Dictionary of Terminology

Revised 02/27/24

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Abamectin A mixture of avermectins which are metabolic products of Streptomycaes avermitilis. It is an effective anthelminthic and insecticide. See avermectin. ivermectin.

Abaxial Not situated in the line of the axis. Directed away from the axis.

abd Anal body diameter, body diameter at level of anus, used as a measure of distances between structures, or size of structures, in posterior region, usually of females.
Abduce To draw or lead away.
Abduct To draw away from a position near or parallel to the median axis.
See adduct.
Abduction A drawing away. A retraction. See adduction.
Abductor Muscle Any muscle that draws away from the main axis or extends or draws parts from the body. See adductor muscle.
Aberrant Deviating from the usual type or form. Abnormal.
Abiogenesis The theoretic arising of living from nonliving matter. Spontaneous generation. See biogenesis.
Abiotic Pertaining to or characterized by non- living, inanimate phenomenon or objects.
Abnormal Deviating from the usual type or form. Aberrant.

Abomasum. The fouth stomach of a ruminant which receives food from the omasum and passes it on to the small intestne,  See omasum.
Aboral Remote from or opposite to the mouth.

Aborigines The indigenous fauna and flora of a geographical region.
Abort To arrest embryonic development.

Aborted Unsuccessful development rendering a part or organ unfit for normal function.
Abortion The unsuccessful or imperfect development of any entity or normally present part or organ.
Abortive Unsuccessful embryonic development. Rudimentary.
Abraded Scraped, rubbed or worn away.
Abrupt A sudden transition. Without gradation.
Abscissa (pl. Abscissas, Abscissae) The transverse line perpendicular to the vertical line (ordinate) to show by graphic design the relations of two series of facts.
Absent Buccal Capsule When an embedded buccal capsule has walls of the same consistency as the lining of the esophagus the buccal capsule is said to be absent.
Absorb To take something within the body. See adsorb.
Abullate Lacking bullae. See bullae.

Abundance A measure of the frequency of entities such as species in a community or guild measured in terms of numbers of individuals, biomass of individuals, contribution to ecosystem function or metabolic footprint of the entities.

Abyssal Environments at ocean depths or on the bed of the ocean.
Abyssal Fauna Organisms dwelling at oceanic depths below 6,000 feet, quiet water, complete darkness. See benthnic fauna, pelagic fauna.
Acanthiform-shaped like a thorn. See corniform.
Acaudal Lacking a tail.
Acaudate Lacking a tail.
Accentuation Increased distinctness.
Accessory Certain subordinates that are auxiliary in function, course, etc., to the principal.
Accessory Piece The gubernaculum.
Accessory Sexual Structures The spicules and gubernaculum of the male nematode.

Accidental Host. An organism that accidentally harbors a paraite that is not normally a parasite of that species.

Acclimate To cause or the process of becoming accustomed to a new environment. To acclimatize.
Acclimatize To acclimate.
Acclivous A gentle rise. An upward slope.
Accrescent A gradual increase in thickness toward the apex.
Accretion The manner by which crystalline and certain organic forms increase by growth of external addition, Also, the joining of parts normally separate.
Acerate Needle-shaped. See acerose, acicular, pointed.
Acerose Needle-shaped. See acerate, acicular, pointed.
Acephalous Lacking a head.
Acescence The process of becoming sour.
Acicular Needle-like. Having a long, slender point.
Aciculum (pl. Aciculums, Acicula) A seta.
Acidobiotic Living in an acid environment.
Acidophilic A successful mode of life in an acid environment.
Acidophobic Intolerant of an acid environment.
Aciform-shaped like a needle. See pointed.
Aciniform Formed like a cluster of grapes.
Acoelomate The condition of lacking a true coelom.  That is, the body cavity, if any, is not entirely surrounded by mesoderm.

Acquired Character A character that originates during the life of an organism due to environmental or functional cause.
Acre-foot One foot of water over an acre; 43,560 cubic feet; or 325,851 U.S. gallons.
Acre-Inch One-twelfth of an acre-foot.
Acrocentric Having a subterminal centromere.
Acriniform Having a radiated form.
Active See alacrious.
Acuate Pointed. See pointed.
Acute Pointed. With a sharp terminus. See pointed.
Acuminate Tapering to a slender point. See pointed.
Acuminose Subacuminate.

Adcloacal Situated in the proximity of the cloaca.
Adanal Situated in the proximity of the anus.
Adanal Bursa A bursa which does not enclose the tail terminus. See Leptoderan.
Adanal Copulatory Papillae The adanal supplements.
Adanal Supplements Organs of secretion and attachment adjacent to the anus of some male nematodes, See Figure 5.
Adaptation Modification of an organism or its parts or organs to make it more fit for existence under the conditions of its environment.
Addendum (pl. Addenda) An addition. A supplement. An appendix.
Adduct To draw towards the median axis or one part toward another. See abduct.
Adduction A drawing toward. A drawing together. See abduction.

Adductor Muscle Any muscle that draws toward the main axis or brings parts into opposition. See abductor muscle.
Adeniforn Having the shape of a gland. Gland-like.

Adhesion The attractive force between two dissimilar bodies that are in contact. See cohesion.
Adhesion Tubes Hollow tube-like setae by which some nematodes ambulate on a surface or to adhere to a substrate in a flowing aquatic environment.
See ambulatory setae.
Adhesive Bristles Adhesion tubes.
Adhesive Tube The spinneret.
Aditus A passage or opening as an entrance.
Adnate Grown together especially of unlike parts.
Adsorb To take something upon the surface of a body.
See absorb.
Adult A sexually mature individual. A condition achieved after the fourth molt.
Adunc Inwardly curved. Hooked.
See hamate.
Adventitious Not arising from the usual place. Arising sporadically.
Adventive An introduced species.
Aerate To imbue with air.
Aeration The exchange of air in soil with air from the atmosphere. The composition of the air in a well aerated soil is similar to that in the atmosphere; in a poorly aerated soil, the air is considerably higher in carbon dioxide and lower in oxygen.
Aerial Inhabiting the air. Growing or existing above ground.
Aeriform Of the nature or form of air. Gaseous.
Aerobic Requiring the presence of oxygen to live.
See anaerobic, facultative aerobic, facultative anaerobic, obligatory aerobic, obligatory anaerobic.
Aerolated A situation where the transverse striae enter the lateral fields,
See Figure 17.
Aestivation Dormancy during periods of unfavorable environment.
See dormant.
Afferent Bearing or conducting toward an organ or position.
See efferent.
Affinity Relationship. Attraction. A relation among organisms where plan of organization and structure indicate position in the overall system.

Afrotropical Realm The biogeographical region encompassing tropical Africa and the southern Arabian peninsula.  See Holarctic Realm, Australasian Realm.
Agar A gelatin-like substance extracted from seaweed. Agar is used in culture media to cause it to set.
See agminate.
Agminate Aggregated. Grouped. Clustered.
Agnobiotic Culture A nematode population with one or more kinds of organisms present.
See pure culture, aseptic culture, monoxenic culture, axenic culture, xenic, synxenic, monxenic, dixenic, trixenic, polyxenic.
Alacrious Active. Lively.

Alae (sing. Ala) Longitudinal thickening of the cuticle forming wing-like expansions. See longitudinal alae, cervical alae, caudal alae, bursa, lateral alae.
Alar Relating to or belong to the alae.
Alate Having alae. Possessing lateral fields.
Albumin A class of proteins. One segregate of the cuticle.
Albuminoid Concretion Food reserve deposits found in modified intestinal cells of some nematodes.
Aliform Wing-shaped.
Alimentary Canal The alimentary tract.
Alimentary Tract The tubular food-carrying passage extending from the mouth to the anus. Its parts are oral aperture, stoma, esophagus, intestine, prerectum, rectum, anus.
Aliquot A part of a whole that divides the whole without a remainder,

Allele One of two or more variants of a sequence of nucleotides (or of a gene) that are located at the same genetic locus on a chromosome; a shorthened version of the term allelomorph. See allelomorph, locus.

Allelomorph Often  used in the abbreviated form "allele". See allele..
Alleyway A path or separation between experimental plots.

Allomone A semiochemical, emitted by an organism, which mediates an interaction between species that benefits individuals of a species remitting the signal and harms individuals receiving the signal. See semiochemical, kairomone, synomone, pheromone.
Alloplasm Functionally-specialized living matter differentiated from and less active than protoplasm, as that of cilia.
Allotype A paratype of the opposite sex of the specimen designated as the holotype. See type.
Alternation of Generations See metagenesis.
Alveolate Having pits or cells like a honeycomb.
Alveolus (pl. Alveoli) A small cell, cavity or pit.
Amalgamated Lips Lips fused giving a smooth or nearly smooth contour.
Ambifenestrate In some species of the genus 
Heterodera where the vulval bridge is slender and the hatching pore is typically an hourglass shape. See fenestrate, semifenestrate, bifenestrate, circumfenestrate, See Figure 32.
Ambulacral Spines Ambulatory setae.
Ambulatory Setae Setae, sometimes hollow and tube-like, used in locomotion. See adhesion tubes, stilt bristles, setae.
Amendment Any material, such as lime, gypsum, sawdust, or synthetic conditioners that is worked into the soil to make it more productive. Strictly, a fertilizer is also an amendment but the term "amendment" is used most commonly for added materials other than fertilizer.
Amphicoelous Biconcave
Amphicyrtic Biconvex
Amphid (pl. Amphids) Paired lateral sense organs which generally open to the exterior on or near the lip region. See Figure 2, Figure 4.
Amphid Aperture The opening leading to the pouch of the amphid. See Figure 2, Figure 22, Figure 22.
Amphidelphic Having two ovaries, generally one extending anteriad and the other posteriad of the vulva. See monodelphic, prodelphic, didelphic. See Figure 27.

Amphidial Duct The connecting passage between the amphidial opening and the amphidial pouch.
Amphidial Gland An organ located posterior to the nerve ring a.id connects with the central nervous system through the lateral ganglion.
Amphidial Nerve The nerve extending anteriad from the nerve ring to the amphid.
Amphidial Opening The amphid aperture.
Amphidial Orifice The amphid aperture.
Amphidial Pocket The amphidial pouch
Amphidial Pore The amphid aperture.
Amphidial Pouch The cavity or chamber of the amphid which contains the sensilla. A dilation of the amphidial gland. Sensilla pouch See Figure 2.
Amphidial Tubes The passages containing the amphidial nerves which connect the fibrillar terminals and the sensilla. An extension of the amphidial gland. See Figure 2.
Amphimixis The union of germplasm of two organisms in sexual reproduction.
Ampliation An enlargement.
Ampulla A membranous sac or vesicle.
Ampullate Flask-shaped.
Ampuliform Flask-shaped. Dilated.
Anabiosis Act of being revived, especially after a period of desiccation.
Anabiotic Anabiosis
Anabolism The constructive processes iii metabolism, from digestion to assimilation. See metabolism, catabolism.
Anaerobic Living in the absence of atmospheric oxygen. See aerobic, facultative aerobic, facultative anaerobic, obligatory aerobic, obligatory anaerobic.
Anal Aperture The anal opening.

Anal Body Diameter (Width) The body diameter at the level of the anus; sometimes abbreviated as abd or abw. See Anal Diameter, abd
Anal Cleft The anal opening

Anal Diameter The body diameter at the level of the anus.
Anal Fenestra In the genus Heterodera, the opening resulting from the breakdown of the thin walled, transparent cuticular region of the anus. See Figure 34.
Anal Ganglion Receives the ventral cord and from which the anolumbar connectives extend to the lumbar ganglia.
Anal Muscles Muscle cells/tissue which function to make the anus operative.
Anal Opening The orifice to the exterior at the terminus of the rectum and delimited by the anus.
Analogue A part or organ similar in function to a part or organ of another individual but differing in structure and origin. See homologue.
Analogous Similar in function but differing in origin and structure. See homologous.
Analogy Similarity in function between parts or organs of a different origin. See homology.
Analytical Key The resolving of the characteristics of nematodes into their constituent parts resulting in the selection of a particular specimen.
Anaphase A state in mitosis or meiosis in which daughter chromosomes migrate toward the spindle poles. See prophase, metaphase, telophase.
Anastomosis (pl. Anastomoses) The union or intercommunication of the lumen of a system or network.
Anceps Sword-shaped.

Androdioecious Descriptive of a population expressing the characteristics of androdioecy

Androdioecy The condition in which a population consists of both males and hermaphrodites. See dioecy, trioecy.
Androgynous Combining the characters of both sexes. Hermaphroditic. See hermaphrodite, reproduction.
Androtype A male type. See type.
Aneuploid Having a chromosome number that is not a multiple of the haploid number. See monoploid, euploid, heteroploid, hyperploid.
Aneuploidy The process or history of becoming polyploid.
Angulate Having angles. Angled.

Anion An ion bearing a negative charge. See ion, cation.
Anisoglottid Having the metarhabdions of the glottid apparatus at different levels. See isoglottoid.
Anisomorphic Of dissimilar form, especially pertaining to the metarhabdions of the glottoid apparatus. See isomorphic.

Anisotopic At dissimilar levels, especially pertaining to a glottoid part of the stoma with dorsal part anterior to the suventral parts.

Anlage: The rudimentary basis of an organ or body part in a developing embryo. See embryo.
Annulate Comprising or furnished with rings. Ringed.
Annulations Deep transverse striae which occur at regular intervals in the cuticle.
Annule The interval between the annulations. A transverse ornamentation of the cuticle surface formed by deep striae at regular intervals. Formed of or giving the shape of rings. See Figure 17.
Annulet A small ring.
Annulose Ringed.
Annulus A ring-like structure or marking.
Anolumbar Connectives Connections joining the anal or preanal ganglia with the lumbar ganglia.
Anorectal Connectives Commissures extending from the anal ganglia to the dorsal surface of the rectum joining the dorsorectal ganglion from which a median nerve extends posteriad to the tail.
Antagonistic Symbiosis A symbiotic association which is disadvantageous or destructive to one of the symbionts.

Antarctic Realm The biogeographic region that encompasses Antarctica. See Holarctic Realm
Anteapical Situated just before the apex. Subapical.
Antemortem Before death. See necropsy, postmortem.
Anteriad Directed forward. Opposed to posteriad.
Anterior In front. Before. The front position as opposed to the posterior.

Anterior Cephalic Crown A crown of six papillae or setae located immediately posterior to the labial crown of papillae. See labial crown of papillae, posterior cephalic crown.
Anterior Cephalid The anteriad cephalid at which the two lateral cords arise. See cephalid. See Figure 1.
Anterodorsal Toward the front and dorsum.
Anteroposterior Axis The long axis from head tail. Longitudinal axis.
Anteroventral Toward the front and the ventral.

Antepudendal With genital tube anterior to vulva. See postpudental.
Anthelminthic A compound fatal to worms or causing the expulsion of worms, especially intestinal worms.
Antibiosis An antagonism between two or more organisms, especially microorganisms in soil, to the detriment of one of them.

Antidromic Extending or proceeding in a direction differeing from the usual.  See orthodromic.

Antidromous Changing direction.  For example, antidromously reflexed ovary.
Antipathetic Symbiosis A symbiotic association which is advantageous or necessary to one or both symbionts.
Antrorse In a forward or upward direction. See postrorse, retrorse.
Antrum A cavity or hollow space. A sinus.
Anus The extremity of the rectum. The posterior opening of the alimentary canal. See Figure 18, Figure 28, Figure 29, Figure 41.

Aparity Live birth of juveniles that emerge from eggs that are still in the uterus. See Bagging.
Aperture An opening. Hole. Orifice. The diameter of the opening.
Apex (pl. Apices) A proximal continuation of the aphelenchoid spicule shaft. The tip. The point of culmination.
Aphelenchoid Esophagus Having a narrow procorpus with a strongly formed median bulb followed by a narrow tube which extends to the intestine. A basal swelling is lacking and the three esophageal glands lie outside the esophagus proper.
Apically Near, toward or directed toward the apex.
Apicad Toward the apex.
Apical Cell A cell of the epithelium that forms the gonoduct wall and is situated at the distal end of the ovary and to be differentiated from the terminal cell.
Apical Lip Notches  Indented lip margins at the confluence of the lips.
Apiculate  Abruptly terminated by a fine, distinct point.
Apneuistic Respiration through the cuticle.

Apodeme A ridge or knob on the cuticle of the stegostome of diplogasterid nematodes that provide muscle attachment and movement of the structure,
Apomixis, Apomictic Parthenogensis Reproduction without fertilization and by mitotic division of egg cells. See Parthenogenesis, Mitotic Parthenogenesis.

Apomorphy; Apomorphic Character or Trait A character that is unique to a group or species and that may be unique from, or represent a "recent innovation" from that found in the ancestor.
Apophysate Bearing an apophysis.
Apophysis (pl. Apophyses) A process. A prominence. See Figure 24.
Apotype A specimen, other than the type, upon which a subsequent or amended description or figure is based. Hypotype. Plesiotype. See type.
Apparition Appearance, Visible.
Appendage An external organ or limb.
Appendix An outgrowth or process, especially an addition to what is relatively complete in itself.
Appendicle A small appendage.
Appendicule A large, single, ventral preanal supplementary organ which is extensible.
Applied Nematology Economic nematology. The practical use of pure nematology for control of nematode pests.
Appose To place surfaces opposite each other.
Apposition The condition of having surfaces against each other. See Fornent, juxtaposition.
Aquatic Living in a water habitat. See arenicolous, edaphic, hypogaeic, marine, rheophile, terrestrial, terricolous, xerophilous.

Arakaoderan bursa Caudal alae completely surrounding the cloacal area.  See leptoderan, peloderan.

Arc A bow-like curvature.
Arcade A circular band of tissue which usually surrounds the esophagus at the base of the lips.
Arcade Cells Cells situated along the esophagus, two opposite each esophageal lumen radius and one opposite each sector for a total of nine. The name is derived from the arch-shaped connections at the base of the lips.
Arcadial Tissue A mass of cells surrounding the stoma.
Arch A structure or form usually curved. In perineal patterns of Meloidogyne females the curved formation of cuticular striae above the phasmids. See Figure 28,
Figure 29.
Arcuate Curved like a bow. Arched.
Are A measurement of area equal to 100 square meters or 119.6 square yards.
Area Application Broadcast application of soil nematicides.

Area Rugosa Ornamentation of the cuticle, sometimes present on the ventral surface in front of the cloaca on the coiled part of the posterior extremity of the male.
Arenicolous Inhabiting sand. See hypogaeic, aquatic, edaphic, marine, rheophile, terrestrial, terricolous, xerophilous, fossorial.
Areolate A small area, especially of cuticle, delimited by transverse and longitudinal markings.
Arista A bristle like appendage.
Aristate Having a slender or spiny terminus.
Arrested Growth A stopping of the growth processes.
Arrowhead-shaped See sagittate.
Ascarocollagen The non-hydrolyzed form of ascarogelatin. It corresponds to the fiber, internocortical and fibril layers of the cuticle.
Ascarogelatin A segregate of the cuticle of the collagen group.
Ascarlyose The sugar 3,6-dideoxy-L-arabinohexose.
Asepsis The state or condition of being aseptic. See sepsis.
Aseptic Free of microorganisms. See septic.
Aseptic Culture A nematode population containing a single species only and free of contamination by all other organisms. Aseptic population. See pure culture, pure population, agnotobiotic, axenic, xenic, synxenic, monoxenic, dixenic, trixenic, polyxenic.
Aseptic Population An aseptic culture.
Asexual Reproduction Reproduction where the union of gametes is not involved. See sexual reproduction.
Association Ecologically, uniform groups of strata over a large area.
Asteriform Star-shaped. Like a star.
Atavism Reversion to a more primitive type.
Athrocyte A coelomocyte capable of absorbing foreign material from body fluids and storing it in crystalline form. See coelomocyte.
Atrophy A wasting away or arrested development.

Attacked To be fed upon by nematodes. To become infested with nematodes. See invasion, infective.
Attack Population The pathogenic nematodes per unit of substratum capable of invasion.
Attenuate Thin, Slender, Drawn-out, Extended

Attractant A chemical substance causing a positive migration response.
Attraction A positive response where the mean number of migrating nematodes reaching the plant end of a test chamber is significantly greater (at the 95 percent level of probability) than the mean number reaching the blank end and where this difference occurs within 3 hours in agar or 6 hours in sand.

Auricular Appendages Horseshoe-shaped cuticular forlds in the cephalic region of some nematodes, e.g. Habronematidae.  See Cordons

Australian Realm The biogeographis region that encompasses Auatralia and Pacific Islands.  See Holarctic Realm, Antarctric Realm.

Autapomorphy A situation where all the species of a taxon descended from the same ancestor share the same "innovative" or recent apomorphic trait. See synapomorphy.
Author The writer of a paper, article, treatise, etc. The author's name usually accompanies the paper to gain credit for accomplishment and to affix responsibility.

Autocthenous Infection Infection originating from organisms, or their progeny, that are already within the or around the host. See autoinfection.

Autogamy Self-fertilization, the fusion of two gametes that come from one individual.
Autoinfection The source of infection originates within body of the host. Infection from within by progeny of previous or current parasites. Occurs in both plant and animal hosts.
Autoinoculation The spread of an infestation from a focus of infection to other parts of an organism.
Autolysis Destruction of a cell by internal agents. Self digestion of a tissue.

Automixis, Automictic Parthenogenesis Reproduction without fertilization and with a meiotic reduction division of unfertilized egg cell.  Diploid number may be re-established by fusion of nucleus with polar body.  See Parthenogenesis, Meiotic Parthenogenesis.

Auto-Pseudogamy A form of Pseudogamy, where male sperm is necessary to activate oocytes but DNA is not transferred, in which females produce a small quantity of male offspring to supply their sperm needs.  See Pseudogamy.
Autopsy An examination and partial dissection after death.
See postmortem, necropsy.
Autosome A chromosome which is not a sex chromosome.
Autotomy Self-amputation of the posterior part of the body by some nematode forms on gaining entrance to an animal host.

Autotroph An organism with the ability to create food resources from simple compounds using the energy of the sun; a primary producer. See Heterotroph Photoautotroph, Chemoautotroph

Autotrophic Having the ability to create complex nutritive substances from simple compounds such as carbon dioxide and water using energy from the sun (photoautotrophic) or from chemical reactions (chemoautotrophic). Autotrophs are primary procucers; the energy they capture is used by consumers (heterothrophs).  See Photoautotroph, Chemoautotroph, Heterotroph.
Autotype A specimen identified by the author as an illustration of his species and compared with the type or cotype. Heautotype. See type.

Avermectin(s) A series of 16-membered lactone derivatives of fermentation products of Streptomyces avermitilis. They have effective anthelminthic and insecticidal properties.  See ivermectin, abamectin.
See subulate, styliform.
Axial Belonging to, or around, in the direction of or along an axis, in line with...
Axial Stylet A buccal stylet aligned along the anteroposterior axis.

Axil The angle formed between a branch or petiole and the stem from which it arises; the cleft between two lips. See primary axil, secondary axil, Figure 36
Axis (pl. Axes) A straight line passing through a body about which the parts are symmetrically arranged.
Axon, Axone The long process of a nerve cell conducting impulses way from the cell body.


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Bacillary Bands One or two laterally situated bands of cells of the lateral cords in the esophageal region. See hypodermal glands.
Bacillary Layer A non vibratile form of cilia which line the intestinal epithelium.
Bacteria Consuming See bacteriophagous.
Bacteriophagous Feeding on or consuming bacteria. See feeding.

Bacterivores Organisms that feed on bacteria.
Baculiform Having the shape of a rod or staff.

Baermann Apparatus The funnels and accessories used to implement the Baermann funnel technique.
Baermann Funnel Technique A method of isolating nematodes from soil, screening residue, plant tissue, or other matter where the material is placed in water and the nematodes by their own action move out into the water, settle and are drawn off from tubing attached to the funnel stem.

Bagging Matricidal vivipary (egg hatch within the body of the female), also known as Endotokia Matricida.
Bag-like See saccate.
Ballonets Cuticular inflations in the cephalic region assuming a swollen band shape immediately posterior to the lips. See head bulb.
Banks Groups of peripheral longitudinal muscle cells. Muscle fields.

Barcode A machine-readable representation of data by lines of different widths and spacings; for example, the DNA sequence data that characterize a species. See DNA Barcoding, DNA Metbarcoding.

Basal Related to, located at, or forming the base.
Basal Bulb An enlargement of the esophageal wall, muscular or glandular, at the posterior of the esophagus. See cardiac bulb, bulbous, isthmus, terminal bulb, true bulb, metacorpus, posterior bulb. See Figure 1, Figure 3.
Basal Knobs The posterior knobs of the stylet. See stylet knobs.
Basal Lamella The inner-most cuticular strata which consists of a thin layer which in cross section appears to be striated. See cuticular layering.
Basal Plate The posterior radial apparatus of the cephalic framework.
Basal Ring The posterior circular base of the cephalic framework. See Figure 6.
Base Pair A unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. See nucleobases.

Basiconica Cone sheped

Batatiform Having the shape of a sweet potato.
Bathyal Fauna Organisms dwelling at oceanic depths of 600 to 6,000 feet, quiet water, little to no light. See benthonic fauna, pelagic fauna.
Beaded See moniliform.
Bean-shaped See reniform.
Bearding A condition of excessive root proliferation induced by nematode feeding.

Beet Sickness A disease of sugar beets incited by Heterodera schachtii.
Beet Weariness A disease of sugar beets incited by Heterodera schachtii.
Bell The bursa.
Bell-shaped See campanulate.
Benthonic Fauna Organisms which dwell on the bottom. They are further defined as littoral, neritic, bathyal or abyssal by depth and nature of bottom. See pelagic fauna.
Benthos The sea bottom; the community of organisms at the bottom of the sea..
Besom A broom.
Besomiform Formed or-shaped like a broom.
Biconcave Possessing concave surfaces on opposite sides. See amphicoelous, amphicyrtic.
Biconvex Possessing convex surfaces on opposite sides, See amiphicyrtic, amphicoelous.
Bicorn With two horns. Crescentiform.
Bicornuate Bicorn, with two pointed tips.
Bicron One billionth of a meter (0.000,000,001).
Bifarious Orientated or pointed in two directions.
Bifenestrate In some species of the genus Heterodera the vulval bridge is stout and divides the fenestra so that the semifenestrae appear to be two nearly separate holes. See fenestrate, semifenestrate, ambifenestrate, circumfenestrate. See Figure 32.
Bifid Divided into two equal parts.
Bifilar Having two filaments or fibers.
Biflex Bending in two directions.
Biform Of two forms, Possessing characteristics of two forms.
Bifurcate Divided into two branches. Forked.
Bilaterally Symmetrical An organism in one plane with each side being approximately a mirror image of the other. This plane usually lies anteroposteriorly and dorsoventrally.
Binding Cells Three coelomocytic cells adjacent to the esophagus and opposite the fibril cells, two ventrolateral and one dorsal. See coelomocytes, fibril cells.
Bioassay Quantitative estimation of a biologically active substance by testing its effect under standardized conditions on living organisms or the effect of one organism upon another.
Biodiversity The variety and variability of life in an ecosystem based on variation at the genetic, species, functional or ecosystem levels.

Biogenesis The doctrine that living organisms are produced only from pre-existing living organisms. See abiogenesis.
Biogeny The evolution of organic forms considered individually (ontogeny) or tribally (phylogeny).
Biological Control The limiting of pathogenic nematode population through depredation by natural enemies.
Biological Race A segment of  total species population differing in some physiological characteristic. See biotype

Biomass The weight of living organisms in a given area; often applied as the total weight of organisms participating in a specific ecosystem function or service.  For example, the biomass of bacteriphagous nematodes.

Biophagous Feeding upon living organisms or living tissue. See feeding.
Biosis Life. Vitality.
Biota The fauna and flora of a region.
Biotic Pertaining to life or the laws of animal and plant progress and evolution.
Biotope A region of uniform environment and biotic populations. 

Biotrophic Organism  An organism that requires a specialized feeding site to be kept alive so that it can complete ists life cycle.  See biotrophy,

Biotrophy  A relationship with the host whereby the feeding site must be kept alive to allow the parasite to complete its life cycle.
Biotype A subgroup of organisms which possess the same genetic characteristics. A subdivision of a race.
Biparasitic A parasite upon a parasite. See feeding.
Bipolarity Possessing two poles.
Bisexual The species having two sexes distinct and in separate individuals. See hermaphrodite, gonochoristid, reproduction.
Bisulcate Having two grooves.
Bivulvarity The occurrence of two vulvae on a single female.
Bivalents Paired homologous chromosomes associated with synapsis.
Blackhead Disease of Bananas A disease of banana plants incited by Radopholus similis.
Blackhead Toppling A disease of banana plants incited by Radopholus similis.
Black Root Rot A disease of strawberry incited by Pratylenchus penetrans, fungi and bacteria.
Blasting A failure to produce fruit or seeds.
Blastocoele The cavity of a blastula.
Blastoderm The cell layers formed by the repeated segmentation of the blastomeres.
Blastomere Cells produced by the first few cell divisions. A cell of the blastula.
Blastula The early embryo having the form of a fluid-filled sphere bounded by a single layer of cells. See gastrula.
Blind Bud An abortive flower bud especially one due to nematode infection.
Blind End The closed terminus of a tube or organ. See caecum.
Blinding Destruction of a plant growing point, stem, flower or root by nematode attack.
Blind Plant A plant with a bud or growing point killed by nematode infection.
Blister A vesicle of cuticle or epidermis.
Blister-like See pustule.
Bloat A disease of onions incited by Ditylenchus dipsaci.
Bloom The subcrystaline layer of a waxy nature found on the cysts of some Heterodera spp.
Blunt See obtuse.
Boat-shaped See scaphiform.
Body The nematode frame with its organs. The important and largest part of an organ. as the body of the spicule.

Body Cavity The hollow within the body which contains the internal organs. See pseudocoel.
Body Pores A series of minute depressions slightly submedian or lateral and apparently connected with the lateral cords via small canals. See caudal pores. ventromedian pores, ventrosubmedian pores, excretory pore.
Body Wall The structural frame consisting of cuticle, hypodermis and muscle layer.

Boss A cuticular prominence on the surface of the nematode, See Ventral Boss.
Botryoid Resembling in shape a cluster of grapes.
Bottle-shaped See lageniform, ampullate, ampulliform.
Boundary Layer The cuticular stratum which is distinct only in certain instances and probably is a condensation layer between the matrix layer and the fiber layers. See cuticular layering.
Bounding Membrane A thin syncytial epithelium covering the esophagus.
Bow-like See arc, arcuate.
Brackish Water Saltish, slightly saline.
Brain The nerve ring.
Branched See ramified, ramiform.
Branched Gland A form with outgrowths far exceeding the diameter of the cell body in length.
Breaking Joint The site of autotomy.
Bridging Host
The possible passing from one host to a previously unsuitable host by transition through the intermediation of another, the bridging host.
Brier Bud A disease of strawberry incited by Aphelenchoides fragariae. See dwarf.
Bristle Setae Ambulatory setae apparently non-functioning glands or sensory organs acting as organs of traction. See setae.
Bristle-shaped See arista, setiform.
Broadcast Application The treatment of soil with a nematicide in such a manner that the expanding vapors form a solid carpet throughout the field. Solid application. See row application, spot application, drench application, gas application.
Broken Striae Non-continuous configuration lines of the perineal pattern. See partial striae, lighter striae, intermediate striae.
Broom-shaped See besomiform.
Brown-Leaf Disease A disease of Asplenium nidus incited by Aphelenchoides fragariae.
Brown Ring Disease A disease of daffodils and hyacinth incited by Ditylenchus dipsaci.
Brown Ring Disease of Narcissus A disease of narcissus capable of being incited by Ditylenchus dipsaci, Aphelenchoides fragariae, A. parientinus or Aphelenchus avenae.
Buccal Aperture The oral aperture.
Buccal Capsule Sensu lato, the combined vestibulum and buccal capsule. The stoma. Sensu stricto, the anterior widening of the esophageal cuticular tube often distinguished from the lining of the latter by it more developed cuticularization. See Figure 12.
Buccal Capsule Cephaloboid An elongated, chambered buccal capsule in which the cheilostom is broad and the protostom and telostom narrow while being enclosed by esophageal musculature. See buccal capsule panagrolaimoid.
Buccal Capsule Panagrolaimoid An elongated, chambered buccal capsule in which a short posterior part is narrowed and surrounded by the esophageal musculature. See buccal capsule cephaloboid.
Buccal Cavity A buccal capsule in the broad sense Figure 40 .
Buccal Ring Where present, a thickened ring delimited from the beginning of the buccal capsule by a groove.
Buccal Rod Where present, elongated cuticular thickenings of the buccal cavity.

Buccal Rugae Folds in the wall of the buccal cavity that provide some rigidity; rhabdions. See rhabdions.
Buccal Spear A stomatostyle.
Buccal Stylet A stomatostyle.
Buchner Funnel A funnel with an interior perforated plate and used for vacuum filtration.
Buffered Populations A situation existing whereby organisms affect one another in such a way that the population density of each remains within a certain range about a mean.
Bulb Flap One of three parts of the valvular apparatus. One in a dorsal and two in subventral positions. See Figure 15.
Bulb Flaps The valvular apparatus

Bulb Teeth The valvular apparatus.
Bulbar Valve The valvular apparatus.
Bulbiferous Having the form of a bulb.
Bulbiform Having the form of a bulb.
Bulboid Esophagus Having a cylindrical shape anteriorly and terminated by a basal bulb. Also termed oxyuroid esophagus.
Bulbous Bulb-like.
Bulbs The one or more muscular swellings of the esophagus. See true bulb, pseudobulb.
Bulbus The basal bulb of the esophagus.
Bulla (pl. Bullae) A blister-like prominence near the vulval fenestra of some Heterodera. See Figure 33.
Bullate Having a blistered or puckered form or appearance. Having or bearing bullae. See bullae.
Burden The total number of parasites infecting an individual.
Bursa (pl. Bursae) Wing-like extensions of the lateral cuticle at the caudal end of the male. Caudal alae. See leptoderan, peloderan, rhabtitoid bursa, strongyloid bursa, .Figure 41.
Bursa Copulatrix The bursa.
Bursa Enveloping Tail Peloderan bursa.

Bursal Fan: The spread peloderan bursa of generally rhabditid nematodes,Figure 41 .

Bursal Musculature The arrangement of the muscles pertaining to the bursa. See musculus costae dorsalis, musculus costerum lateralium internis, musculus bursae basalis, musculus costae lateralis externus posterior, musculus costae lateralis externus anterior.
Bursal Nerve Innervated from bipolar sensory nerve cells forming a longitudinal strand on either side in or near the lateral cords.

Bursal Papillae Sensory papillae that support the bursa of certain nematodes (e.g. Rhabditidae). Their patterns and grouping are  of taxonomic signisficance. See Genital papillae, Figure 41
Bursal Ribs See rays, Figure 41 .
Bursate Having a bursa.
Byssus Elaborately-branched polar projections of the protein membrane on eggs of some nematodes.

 Return to Dictionary Index



Cabbagy Plant A disease of teasel incited by Ditylenchus dipsaci.
Caecum (pl. Caeca) A cavity open at one end, the blind end of a lumen or duct.

Caliciform Having the shape of a calyx or a cup.
Calvarium Subcuticular cephalic framework. See Figure 1.
Camera Lucida An optical instrument for use with the compound microscope where by means of prisms and mirrors a virtual image appears as if projected upon a plane surface. Used for pencil sketching and measuring.
Campanulate Bell-shaped.
Campanuliform Having the shape of a bell.
Canal A tubular channel or passage. A duct.
Cane A thickening with a lack of ornamentation of the posterior cuticle. See helmet.
Cap Cell The terminal cell of the ovary. The primordial germ cell. See Figure 27.
Capitulum A sclerotized guiding piece for the gubernaculum on the ventral cloacal surface of some Hoplolaiminae. The manubrium of some authors. See telamon, See Figure 20.   Alternatively, ptoposed for dorylaimoid spicules, the head of the spicule from the proximal end to the start of the blade or lamina - the manubrium of some authors.
Capsula Var. of capsule.
Capsule A receptacle or bag. A membrane or sac-like form enclosing a structure or organ.
Cardia A muscular structure at the base of the esophagus opening into the intestine. See esophageal-intestinal valve, cardiac valve.
Cardiac Bulb The basal bulb of the esophagus. See cardia.
Cardiac Caecum The esophageal caecum.
Cardiac Esophageal Bulb The basal bulb of the esophagus.
Cardiac Glands Three glandular bodies located at the base of the esophagus.
Cardiac Region of the Intestine The anterior portion of the intestine as distinguished from the prerectum.
Cardiac Valve A thickening or complication of the esophageal lumen lining in the basal bulb. See cardia.
Cardiac Bulb The basal bulb.

Careen A left dorsal cuticular dilation supported by the left ridge and adjacent dorsal ridge of the synlophe in strongylid nematodes. See synlophe
Carina (pl. Carinae) An elevated ridge or keel-like structure not necessarily pronounced or acute.

Carinate Keeled. Having one or more longitudinal ridges.
Carnivore A flesh eater. A predaceous nematode. See feeding.
Carnivorous Preying or feeding on nematodes or other animals. See feeding.
Carrier An organism bearing internally an infectious agent of disease even though no marked symptoms are evident. See vector.
Castration Any process which prevents the development of mature ova or sperm in the gonads.
Catabolism The destructive processes in metabolism. The breaking down of more complex components in protoplasm. See metabolism, anabolism.
Cation An ion bearing a positive charge. See ion, anion.
Caudad Toward the tail. Opposed to cephalad.

Caudal Belonging to, or like, a tail. Situated on or near the tail.
Caudal Alae The bursa. Alae confined to the posterior part of the male nematode body. See alae.
Caudal Appendage In mermithids, the terminal portion of the larval tail. See terminal spine, caudal papillae.
Caudal Bursa A bursa which completely encloses the tail. Peloderan.
Caudal Flagellum A more or less filiform, long and thin elongation of the tail of uniform diameter, or becomes a caudal thread which is pointed at its tip.
Caudal Glands Usually three elongate unicellular cells in or near the tail, discharging by separate ducts into a common ampulla at the spinneret. See Figure 7.
Caudal Papillae In mermithids, the terminal portion of the larval tail.
Caudal Papillae See submedian caudal papillae. See
Figure 5, Figure 18.
Caudal Pore The spinneret. The outlet of the caudal glands.
Caudal Wing The bursa.
Caudalid A single structure similar in size, morphology and body position as the hemizonion and located slightly anteriad of the anus. A parahemizonid.
Cauliflower Disease A disease of strawberry incited by a synergistic association of an Aphelenchoides nematode and bacterium, Corynebacterium fascians. Cauliflower dwarf.
Cauliflower Dwarf Cauliflower disease. See near cauliflower.
Causal Agent The parasitic organism responsible for a disease. Causal organism.

Causal Organism The organism that produces a given disease. Causal agent.
Causative Agent See causal organism.
Cavate Hollowed out.
Cavernicolous Cave-inhabiting. See arenicolous, hypogaeic, aquatic, edaphic, marine, rheophile, terrestrial, terricolous, xerophilus.
Cavernous Filled with caverns. Divided into small spaces.

cbd Cloacal body diameter, body diamter at level of cloaca, used as a measure of distances between structures, or size of structures, in posterior region of males. See cloacal body diameter.
Cecum (pl. Ceca) An outpocketing of the intestine at the anterior end, rarely composed of twists or loops. See caecum.
Ceiling The maximum population density for a given set of circumstances.
Cell The structural and functional unit of all plant and animal life. It consists of protoplasm, a nucleus and is surrounded by a membranous wall.
Cell Body The portion of a cell that contains the nucleus. In a nerve cell it is different from the region comprising the axon or dendrites.  See soma.

Cell Constancy A situation in nematodes where the multiplication of cells ceases at hatching, except for the reproductive system, and growth is by enlargement of existing cells.

Cell Grazer A nematode that withdraws the cytoplasm from a cell and then moves to another cell;  feeding from cels without requirineg development of a nurse cell system.  See biotrophic organism.
Cell Membrane A differentially permeable membranous surface which surrounds the cell.
Cellules End organs or terminal bodies of some coelomocytes.
Central Area The nonstriated region anteriad of the vulva and posteriad of the cutcular striations in Meloidogyne perineal patterns. See Figure 28, Figure 29.
Centromere That part of a chromosome to which the spindle fiber apparently attaches in mitosis.
Centrosome A minute protoplasmic body in the cytoplasm or nucleus that plays an important role in mitosis.

Cephalad Towards the head.

Cephalated Having the head set off in some manner.

Cephalic Belonging to, or situated in, on or near the head. Directed toward the head.

Cephalic Adhesion Tube  A tube for sececreting adhesive material located in the cephalic region. See adhesion tube.
Cephalic Arches See ribs.
Cephalic Capsule A strongly cuticularized head set off by a groove.

Cephalis Cirrus (pl. Cirri) One of the elaborate cephalic appendages in front of the cephalic setae.
Cephalic Crown of Sensory Organs The circular arrangement of papillae, etc. about the oral opening See anterior cephalic crown, posterior crown, inner circle, outer circlet.
Cephalic Framework A rigid supporting structure which provides form to the head and axially acts as a stylet guide. See calvarium. See
Figure 1, Figure 6.
Cephalic Glands
Lateral glands opening near the cephalic papillae.
Cephalic Organ The head cleft.
Cephalic Papillae Papillae of the outer circlet about the mouth. Se
e Figure 22.

Cephalic Probolae Six processes surrounding the mouth opening in some cephalobids and probably extensions of the lips; distinct from labial probolae. See labial probolae.
Cephalic Setae Setae of the outer circlet about the mouth. See Figure 22, Figure 23..

Cephalic Slits Paired pouch-shaped cephalic sense organs.
Cephalic Suture The posterior delimitation of the cephalic capsule; the offset groove from the body contoure..
Cephalic Tubers Prominences located in the head in labial and cephalic positions, often elaborately developed.
Cephalids Structures of a highly refractive nature, biconvex in longitudinal section and extending around the nematode body in the cephalic region. See anterior cephalid, posterior cephalid, caudalid, hemizonid, hemizonion, parahemizonid.

Cephalization: The tendency for sensory structures and the nervous system to be aggregated anteriorly.
Cervical Pertaining to, belonging to or situated in, on or near the neck.
Cervical Alae Alae confined to the "neck region" and are known only in the parasitic groups Strongylina, Ascaridina and Spirurina.
Cervical Duct The excretory duct.
Cervical Expansion Expansions of the cuticle in the cervical region e.g., in Wilsonema. See cervical.

Cervical Gland The excretory gland.
Cervical Groove A pronounced transverse groove on the ventral surface of the cervical region, in some forms extending to completely encircle the cervical region.

Cervical Lacuna A space (lacuna) between the cuticle and epidermis probabl;y created by differences in contractility of the two surfaces See Lacuna.
Cervical Papillae Paired lateral tactile receptors situated near the nerve ring. Deirids.
Cervical Pore The excretory pore.
Cervical Vesicle Inflated cuticle anterior to the cervical groove.
Challange A test of immunity to a host by exposure to parasites after specific immunization.
Checkered See tessellate.
Cheek An ampulla of an amphid.
Cheeks In Meloidogyne kikuyuensis the heavily striated overlap of perineal cuticle on each side of the vulva. See Figure 28.
Cheilorhabdions The dense cuticular walls of the cheilostom. See Figure 10.
Cheilostom The lip cavity of the stoma, delimited anteriorly by the oral aperture posteriorly by the protostom; the anterior region of the stoma. See protostom, telostom, Figure 40

Cheilostome Alternative spelling of cheilostom.
Chelate A type of chemical compound in which a metalic atom is firmly combined with a molecule by means of multiple chemical bonds.

Chemoautotroph An organism that  uses the energy released from inorganic chemical compounds to build organic compounds.  See Autotroph, Photoautotroph, Heterotroph.
Chemokinesis Stimulation of random movement induced by a chemical agency.
Chemoreceptors Anteriorly the amphids, posteriorly the phasmids. See tactoreceptors.
Chemotropism A movement of turning or curvature induced by a chemical stimulus. See tropism.
Chemotaxis A change of position toward or away from a source of chemical stimulation. See taxis.
Chewing Plates The valvular apparatus. See grinder, Figure 40
Chimney See soil chimney.

Chirotype The type specimen upon which a manuscript name is founded. See type.
Chisel A tillage machine with one or more soil-penetrating points that can be drawn through the soil to loosen the soil or subsoil.
Chitin The substance composing the exoskeleton of insects which is not equivalent to the cuticle of nematodes but is present in egg shells of some forms. See cuticle.
Chitin Plates The valvular apparatus - probably a misnomer in terms of the constituent material of the plates .
Chords Var. of cords,
Chorion The outer shell or covering of a nematode egg.
Chromatid During prophase and metaphase of mitosis or meiosis one of the two strands prior to separation which resulted from duplication of a chromosome. After separation each chromatid is known as a daughter chromosome.
Chromatin Minute granules of a nucleo-protein constituent of a cell nucleus.
Chromosome One of the fundamental bodies into which chromatin resolves itself prior to the mitotic or meiotic division of a cell.
Cicatrix (pl. Cicatrices) A scar or scar-like marking, especially in mermithids.
Cicatrization Tissue Tissue involved in the process of healing a wound.
Ciliate Provided with cilia.
Circa-Equatorial About the equator. About or near the middle.
Circinate Ring-shaped.
Circlet A small circular arrangement of structures or parts. A crown.
Circomyrian A type of muscle cell in which the muscle fibers completely surround the sarcoplasm. See platymyarian, coelomyarian.
Circumfenestrate In the genera Heterodera and Globodera where the vulva is lost when fenestration occurs by the breakdown of the thin cyst wall around the vulva leaving a circular hatching pore. See fenestrate, semifenestrate, bifenestrate, ambifenestrate. See Figure 30.
Circumenteric Ring The nerve ring.
Circum-Esophageal About or surrounding the esophagus.
Circum-Esophageal Commissure The nerve ring.
Circum-Oral About or surrounding the mouth.
Cirrus (pl. Cirri) One of the elaborate cephalic appendages in front of the cephalic setae.
Cirrus (pl. Cirri) A slender appendage formed by the eversion of a very long cloaca, frequently lined with spines.
Citron-shaped Having the form of a large lemon.

Clade A branch of a cladogram that includes a single common ancestor and all of its descendants. See monophyletic.

Cladist An evolutionary biologist who studies the pattern  of species relationships; one who seeka to develop natural classification systems.

Cladistics The classification of organisms according to the proportion of measurable characteristics that they have in common; assumes that the higher the proportion of characteristics that two organisms share, the more recently they diverged from a common ancestor. See apomorphy, speciation.

Cladogram A diagram showing the degree of genetic relationship among organisms.
Classification The systematic arrangement of organisms into groups usually based on natural relationships. The common categories in diminishing rank are phylum, class, order, family, genus, species and variety.
Clavate Club-shaped.
Clavate Cells Modifications of the hypodermis which contribute to the formation of the lips, being two in each lip and they are long cells with a hollow interior, lamellate with expanded distal ends that fill the convexity of the lips.
Claviform Club-shaped. Clavate.
Clay As a soil separate, the mineral soil particles less than 0.002 mm. in diameter. As a soil textural class, soil material that contains 40 percent or more of clay, less than 45 percent of sand, and less than 40 percent of silt.
Clay Loam Soil material that contains 27 to 40 percent of clay and 20 to 45 percent of sand.

Clear To make the cuticle and other body parts transparent or translucent.
Clear Tail Length That portion of the tail peculiar to some nematode larvae in which no internal bodies, structures or arrangements can be seen. See tail terminal.
Cleavage Following fertilization, a repeated subdivision of the zygote cytoplasm with the corresponding nuclear mitosis. See Segmentation.
Cleft The space caused by a slit, splitting, a crack, a fissure, etc. See suture.
Clintheriform Having a shape like a plate.

CLM See Cutaneous Larva Migrans
Cloaca In the male a common chamber lined with cuticle which receives the products of the intestinal and reproductive tracts and empties to the exterior via the cloacal orifice. The hind gut. See rectum.

Cloacal Body Diameter Body diameter at level of cloaca, used as a measure of distances between structures, or size of structures, in posterior region, of males. See cbd, abd.
Cloacal Cuticle The cuticular linings of the cloaca which differs in some respects from the external cuticle. See external esophageal cuticle, rectal cuticle, vaginal cuticle.
Cloacal Evaginations Spicule pouches which secrete and lodge the spicules.
Cloacal Orifice The opening of the cloaca

Cloacal Papillae Tactile receptors in the region of the cloaca. See Figure 41
Cloacal Prominence A posterior projection of the region around the cloacal orifice in some nematode forms. The genital cone.
Clone A group of plants derived from a single plant by means of vegetative propagation. Each individual of a clone has the same heredity, so that in a uniform environment a clonal line of plants will respond rather uniformly. See strain.
Clover Sickness A disease of clover incited by Ditylenchus dipsaci.
Club-shaped See clavate, waddiform.
Clustered See agminate.
Clypeiform Having the shape of a shield. See scutate, scutiform, escutcheon-shaped.
Coarse Root. A condition where most of the lateral roots are killed back by nematode attack resulting in an open system of mostly the main roots.

Cobb Formula A system of measurement utilizing decimal formula in which the measurements stated as percentages of the total length of the nematode are made at the specific body points as follows:

Stylet length

Nerve ring

Esophagus base



as % of body length

Body width at lip region

Body width at nerve ring

Body width at esophagus base

Body width at vulva

Body width at anus

 For the male the letter "M" marks the middle of the body. See de Man formula.
Cockles Galls produced by some species of Anguina, especially A. tritici of wheat kernels. See purples, peppercorns.
Coelomate Having a body cavity. See pseudocoelom.
The main body cavity in which the intestine is suspended.  Surrounded entirely by tissues of mesoderm origin.

Coelomocytes Cells lying in the pseudocoelom and appear not to be part of the general connective or isolation tissue. They apparently are of mesenchymatous origin. See athrocytes, fixed athrocytes, phagocytes, stellate cells, pseudocoelocytes.
Coelomyarian A type of muscle cell in which the muscle fibers are adjacent and perpendicular to the hypodermis and extend along the sides of the muscle cell for varying distances. See platymyarian, circomyarian. See
Figure 9.
Coevolution The process in which two or more species reciprocally affact each other's evolution through natural selection. See speciation.

Coexistence Living together in the same place.
Cohabitants Organisms dwelling together.
Collaret A band-like cuticular extension of the cephalic region opening anteriorly.
Collarette A posterior elongation of the annular ring.
Collum A neck or neck-like part or process.
Collum Testis A narrowing separating the testis from the deferent ducts.
Collum Uteri The constriction which separates the uterus from the vagina. In some forms it is elongated to form the ovijector. See
Figure 24.

Colonizer-persister (Bongers' c-p) series A series of categories of nematodes based on their life history chracteristics, response to enrichment and sensitivity to environmental perturbation.

        c-p1 - Nematodes with short generation time and rapid reproducive rates, respond rapidly to resource enrichment, opportunists, r-strategists.

      c-p2 - Nematodes with relatively short generation time that are tolerant to environmental disturbance and resource limitation.

      c-p3 - Longer generation time and greater sensitivity to disturbance.

      c-p4 - Longer generation time, greater sensitivity to pollutants; usually larger-bodied.

      c-p5 - Large bodied nematodes with long generation time, low fecundity and high sensitivity to environmental disturbance and pollution.
An assemblage of nematodes living in close association, especially of the same species and particular niche.
Column-like See rachis.
Combs Crests of cuticle which frequently bear spines.
Comb-shaped See pectinate.
Commensal An organism not truly parasitic capable of living harmoniously in, with or on another.
Commensalism The mode of different organisms living harmoniously together.
Comminute To breakdown into minute particles. Pulverize. See triturate, macerate.
Commissure A bundle of nerve fibers connecting ganglia.
Common Canal The excretory duct.
Compatible Host-Parasite Relationship  Interaction between a nematode species and host plant that is favorable for nematode survival and reproduction.  See incompatible.

Complete Metamorphosis The young hatch looking unlike the adult and through successive larval instars increase in size through several molts. The pupa or resting stage is entered where the body tissues break down and new structures for the adult arise. See metamorphosis, incomplete metamorphosis.
Concave Hollow. Incurved, as the inner surface of a curved surface or line.
Concavo-convex Having one surface concave the other convex with the convexity exceeding the concavity.
Cone The posterior segment of a female cyst of the genus Heterodera.
Cone A solid body having a circle for its base and terminating in an apex.
Congeneric Of the same genus.
Conical Cone-shaped.
Connective The cords of nerve fibers connecting one ganglion of a nervous system with another.
Conoid Having the shape of a cone.
Conspecific Of the same species. See infraspecific.

Constitutive Characters The suite of derived characters that are comprise to the monophyly of a clade. See clade, monophyly.
Constriction Said of the junction of the head and the cervical region when delimited by a sharply pronounced groove. See depression. See  Figure 6.  
Constrictor Vulvae Muscles which function to close the vulva. See dilator vulvae.
Contaminate To infect or infest, with a pest an otherwise healthy organism. To pollute.
Contaminators Individuals of the inoculum. Organisms which bear the inoculum.
Contort To twist upon itself. To form into curves.
Contraction Swellings Numerous deeply staining enlargements formed at intervals along a muscle contractile fiber.
Control The reduction, by any means, of a plant pathogenic nematode population density which results in an economic increase in crop yield. See soil sterilant, spectrum.
Convergence A resemblance between individuals or structures derived from different ancestries or origins. Lines of development coming together from diverse origins to form similar characters. See divergence.
Convex A surface or line curved or rounded as the exterior of a sphere or circular form.
Coprophagous Feeding on dung. See feeding.

Copulation The act of sexual intercourse.
Copulatory Apparatus The copulatory armature.
Copulatory Armature The sex organs of the male employed in the act of copulation. See spicule, gubernaculum, supplementary papillae
Copulatory Muscles In most male nematodes specialized transverse muscles of varying numbers extending from the lateral cords to the subventral sides of the body, generally anterior to the cloacal orifice. The ventral curvature of the posterior part of the body in fixed material is caused by these muscles. See bursal muscles.
Copulatory Warts Greatly enlarged genital papillae of some male nematodes.
Cord-like See restiform.
Cordons Specialized, ribbon-shaped, paired bands of cephalic cuticle; horseshoe-shaped cuticular folds or Habronematidae. See epaulets.
Cords Four longitudinal lines of hypodermal thickening lying on the inner side of the hypodermis and variously termed the dorsal, lateral and ventral cords. The cords contain the nuclei of the hypodermis. See intercordal areas.
Coriaceous Tough, leather-like.
Cornein The horny substance of corals and not equivalent to the cuticle of nematodes. See, cuticle.
Corniform An extended mucronate or pointed process like the horn of an ox.
Cornu (pl. Cornua) Modified cephalic seta(e) with leaf-shaped appearance and often with incisures of the edge, exytending forward and inward.  See corona, corona radiata, perioral.

Corona A crown-like structure or process. A crown.
Corona Radiata Modified lips which form an upstanding collar with the inner surfaces having numerous lobes or cuticular teeth, sometimes compounded with an inner leaf crown. See Figure 12.

Coronoid Beak-like
Corpus The most anterior segment of the esophagus of cylindrical form and of moderate width. Sometimes the base is swollen to form a bulb in such instances the corpus may be divided into procorpus, mesocorpus and metacorpus.
Corpus Esophagi The corpus.
Corridor A passage or tunnel made by an animal. See gallery.
Corrugated Wrinkled. Formed of alternate ridges and grooves.
Cortex Layer The outer layers of the cuticle. See matrix, fiber layers, cuticular layering.
Cortical Consisting of, or belonging to the cortex.
Coryogamy Var. of koriogamy.
Cosmopolitan Common everywhere. Widely distributed. Found in most areas of the world. See ecumenical.

Cospeciation A form of coevolution in which speciation of one species dictates that of another; it is most commonly studied in host-parasite relationships. howqever, host-parasite phylogenies may be altered by host switching, extinction, independent speciation, and other ecological events, so that cospeciation harder to detect. See coevolution, speciation, Fahrenholz's rule, phylogeny.
Costa (pl. Costae) A rib or rib-like structure.
Costate Having the appearance, structure or form of a rib or ribs.
Cotype Any one of all the specimens available when a species is named, hence the type equals the sum of the cotypes. See type.
Coupled Annules Adjoining annules are inserted into one another providing added rigidly and allowing elasticity.
Crenate Having a margin formed of rounded scallops.
Crenation A rounded projection.
Crenature A rounded projection, also, the indentation between crenations.
Crenulate Minutely crenate.
Crescent Sickle-shaped, like the new moon with convex and concave edges.
Crescentiform Having the shape of a crescent.
Crest A ridge or linear prominence. See carinate.
Cristate Having a prominent crest. Crested.
Cristiform In the shape of a ridge or crest.
Cribriform Perforated like a sieve.
Crimp A pathological condition incited by nematodes where plant parts are crinkled, twisted and distorted.
Crimp A disease of strawberry incited by Aphelenchoides fragariae.
Crop Rotation The sequence of plants grown in a particular field.
Cross Breeding The mating of two varieties of the same species. To hybridize.
Cross Infection The infestation of another individual of the same species.
Cross Section A transverse cut. A cut of an organism or thing at right angles to the longitudinal axis.
Crowding Effect A situation where the average size of individuals is reduced in multiple infestations.
Crown A circular structure or process or arrangement of such structures or processes generally at or near the summit of an organ or part. See corona, circlet.
Cruciate Cross-shaped.
Cruciform Cross-shaped.
Crumb An aggregate of soil particles.

Crura The legs of an animal, or the legs of a structure, e.g. a gubernaculum with two parallel guiding rods or rails. See gubernaculum.

Crustformeria A specialized region ibetween the ovary and uterus where the egg shell is deposited.
Cuff A widened glide path of the gubernaculum to help guide the spicule.
Cuirass A protective covering such as the cuticle.
Cuirasse A helmet-like appearance of the cuticle of the head.

Cultural Services Ecosystem services that provide non-material benefits, including recreational opportunities, aesthetic experiences and spiritual enrichment of humans.
Cuneiform Wedge-shaped. See sphenoid.
Cup-shaped See cupuliform, cyathiform.
Cupuliform Having the shape of a cup. Cyathiform.
Curds Dried masses of Ditylenchus myceliophagus and others similar to nematode wool.
Curly Leaf A disease of strawberry incited by Aphelenchoides fragariae. See dwarf, crimp.
Curly Tip A condition where nematode feeding near a root tip causes retardation of growth and the elongation on one side results in a curling effect.
Cusp A pointed process. See pointed.
Cuspate Pointed.
Cuspidate Terminating in an acute point.

Cutaneous Larva Migrans (CLM) A human skin infection in which humans are accidental hosts for larvae of various species of hookworm (family Ancylostomatidae) that are parasites of wild and domestic animals. See Visceral Larva Migrans, Neural Larva Migrans.
Cuticula Cuticle.
Cuticle The noncellular external covering of the nematode and apparently connective tissue of the hypodermis. The cuticle lines the natural opening of the body i.e. the oral cavity, the anal aperture, the vulva, the vagina, the lumen of the esophagus, the rectum, the cervical pore, and the cuticular ampulla of the cervical pore. See hard cuticle, soft cuticle.
Cuticular Adornments Cuticular ornamentations.
Cuticular Framework See frame work.
Cuticular Layering Structural strata of which the cuticle is composed. See external cortical layer, internal cortical layer, fibrillar layer, matrix layer, boundary layer, external fiber layer, basal lamella.
Cuticular Ornamentation Markings of any type on the cuticle.
Cuticular Protuberance Any of a number of modifications of the cuticle, i.e. probollae.
Cuticular Rods In the lip region of some forms the stylet is surrounded by short longitudinal cuticularized rods forming a kind of guiding sheath. Modified cheilorhabdions.
Cuticular Wing A segment of a complicated Tylencholaiminae stylet.
Cuticularized Formed of cuticle.
Cutin A compound related to cellulose and not equivalent to the cuticle of nematodes. See cuticle.
Cutting Organ See onchia, odontia, jaws, denticle.
Cyathiform Concave. Cup-shaped. Cupuliform.
Cylindrical Esophagus Of a large diameter and uniform in width throughout. Characteristic of rapacious nematodes.

Cylindrus The expanded basal portion oof the dorylaimid esophagus (pharynx)
Cyst At maturity the body wall of the Heterodera female thickens, becomes resistant to decay, and turns brown as the worm dies, resulting in a protective shell for the eggs and is termed a cyst.
Cyst Cone The conical perineal region of cyst- forming nematodes.
Cyst-Forming Nematode Any species of the genera Globodera and Heterodera.
Cytogenetics The study of the structural basis of heredity and variation.
Cytokinesis The changes affecting cytoplasm of a cell undergoing mitosis, meiosis and fertilization. See karyokinesis
Cytology The study of the structure, organic processes, functions, etc., of cells.
Cytolysis The dissolution or destruction of cells.
Cytophagous Feeding on cells. See feeding.
Cytoplasm The protoplasm of a cell exclusive of the nucleus and cell wall.


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Damage Year The growing season in which a crop sustained injury due to nematode parasitism.
Dauer Larvae A quiescent stage entered by larvae while enclosed in the cast cuticle of the previous stage.
Decant To gently pour off a liquid in such a manner as not to roil or disturb that remaining.
Decantation-Sieving Method. The gravity-screening method of nematode isolation.

Decapitate To remove the head. To behead, Decollate.
Decay A putrefactive change. The ultimate catabolic state. To rot.
Decline A condition of progressive deterioration of tree foliage and branches.
Decoction A condensing especially by steeping. An extract obtained by boiling.
Defecate To void excrement.
Definitive Complete. Fully developed.
Definitive Home The site of permanent attachment or lodging of parasitic nematodes after a period of larval wandering or migration.
Definitive Host The host in which the sexual life of a parasite takes place.
Degenerate Esophagus An esophageal region showing little or no evidence of its triradiate character or muscular tissue.
DEGO Dorsal esophageal gland opening into esophageal lumen, the position is taxonomically important, especially in the order Tylenchida. See dorsal esophageal gland orifice, DGO, DPGO. Note: esophagus as alternate terminiology for pharynx.

Degeneration Breakdown of the tissues of the internal organs. See devolution.
Dehydration The removal of water, See desiccation, exsiccate.
Deirids Exceptionally large cervical papillae. Lateral tactile receptors situated in the lateral field near the nerve ring.
Delicate Of slight or thin characteristics.
Deltoid Triangular in shape.
De Man Formulae A system of measurement used in identification based on proportional morphometrics. Originally developed by De Man but other parameters have been added by subsequent users, some useful for specific taxa.

       n = number of specimens
      L = body length in mm or µm

      a = (overall body length)/(greatest body width (generally at the vulva))

      b = (overall body length)/(esophagus length from the lips to the esophageal intestinal valve)

     b' = (overall body length)/(esophagus length from the lips to end of the esophageal glands)

      c = (overall body length)/(length of tail (anus to tail terminus))

     c' = tail length / tail diameter at anus or cloaca

     s = stylet or spear length (stomatostyle or odontostyle)

    MB% = (distance from anterior end to median bulb x 100)/(length of esophagus)

     SE = distance from anterior end to excretory pore in µm

     SE/L = SE/L (measured in same units) expressed as %).

     SV/s = distance from base of stylet to median bulb valve/stylet length.

     s/L = stylet length/body length (measured in same units as %).

     m = conus of stomatostyle/total stomatosyle length

      o = (distance of dorsal esophageal gland opening from stylet knobs x 100)/(length of stylet)

      p = (distance of phasmid(when not erratic) from anus x 100)/( length of tail)

     pa = (distance of anterior phasmid (when erratic) from lips x 100)/(overall body length)

      pp = (distance of posterior phasmid (when erratic) from lips x 100)/(overall body length)

      G1 = (overall length of anterior ovary from vulva x 100)/(overall body length)

      G2 = (overall length of posterior ovary from vulva x 100)/( overall body length)

      V = (distance of vulva from the lips x 100)/(overall body length)

     VA = distance from vulva to anus

      stylet extension (odontophore) length in µm
      gubernaculurn length in µm
      spicule length in µm
      capitulum length in µm

    R = total number of body annules

     Rex = number of body annules between anterior and excretory pore

     RV = number of body annules between vulva and tail tip

    Ran = number of body annules between anus and tail tip

     RVan = number of body annules between vulva and anus
For example (the range is given within the parentheses,  the % sign is frequently omitted):

Measurements: (n = 20 females) L = l .17 mm (0.194 1.37 mm); a = 31.3 (26.7-34.6); b = 8.5 (7.9-10.0); b' = 6.3 (5.4-7.5); c = 69 (53.91); o = 14% (10-17%); P = 45% (42.47%): G1 = 36.2% (28.2-48.7%); G2 = 33.1 % (25.5-38.5 %); V = 56.5 % (54-61 %); stylet=43.l (38.2-44. 5 µm). (n = 16 males) L = 9.6 mm (0.74-1. 16 mm); a = 29.2 (26.3- 36.4); b = 7.7 (6.9-8.5); b' = 6.9. (5.4-7.4); c = 34 (29-37); o = l3 %, (10-13 %); P = 42 % (41.1- 46 %);T = 38 % (34-54 %); stylet = 41.4 µm (39.4-43.3 µm); spicules=48 µm (42-52 µm); gubernaculum = 24.7 (20.4-28.6 µm); capitulum = 18.8 µm (16-20.2 µm).
DeManian System A system of vessels connecting the intestine and uteri with one another and posteriorly with the exterior.  Also used for a group of tubes near the anus of certain female nematodes that secrete a sticky substance which protects the eggs or functions during copulation.
De Man Indices See De Man Formulae.
Demarcation Marked by bounds. Delimited. A separation.
Dendrites Branching cytoplasmic projections of a nerve having synapses with axons of other nerve cells.
Denematize To divest of nematodes.
Dentate Bearing teeth. See edentate.
Denticle A small tooth or projection.
Denticulate Having minute tooth-like projections.
Dentiform Having the shape of a tooth.
Dentigenous Ridges Elevations bearing small tooth like projections.
Dentoid Tooth-shaped.
Deoxyribonucleic Acid See DNA.

Depauperate Lacking in abundance or variety of species in an ecosystem.

Dependent Hatching The need for an external stimulus for hatching to be affected.
Depresssion Said of the junction of the head and the cervical region when delimited by a more or less broad hollow. See constriction.
Depressor Ani The H-shaped muscle which serves to dilate the rectum and elevate the posterior lip of the anus thus permitting defecation.

Derived Character A trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants. See Primitive Character.

Dermal LD50  The dosage of a chemical, based on the mass of the affected organism, at which 50% of the target organisms are killed when the material is in contact with the skin; for example, 10 mg of chemical per Kg of target organism tissue. See Lethal Dosage.
Desiccate To dry up. See dehydration. Exsiccate.
Desiccation The state or condition of being dried up.

Desmen A ring of sedimentary material, cemented (by desmos) on the outer surface of a nematode of the family Desmoscolecidae; the body is covered by desmen rings.

Desmos A cement material that holds together the sedimentary particles comprising a desmen.
Detritophagous Feeding on detritus. See feeding.
Detritus The disintegration products of decomposition.
Deutoplasm The food plasm of an ovum. The yolk.
Deutoplasmatic Inclusion A granule or crystal in the yolk.
Devoid Lacking something. Not bearing something.
Devolution Retrograde development. Degeneration.
Dew Point The temperature at which the liquefaction of a vapor begins. Usually the term is applied to condensation of moisture from water vapor in the atmosphere.

DGO Dorsal  gland opening into esophageal lumen or stoma, the position is taxonomically important, especially in the Tylenchida. See DEGO, DPGO.
Dignosis (pl. Diagnoses) A critical scrutiny or presentation of those characters which differentiate the species (or other group) from its closest relatives.
Didelphic Having two ovaries. See amphidelphic, monodelphic, prodelphic, opisthodelphic, polydelphic, reproduction. See Figure 27.
Didymous In pairs. Two fold.
Dieback A condition of progressive necrosis of branch terminals of trees and other plants.

Differentiation The diagnosis of a taxon.
Differentiation The act or process of characterizing or making different. Changing from general to special characters. Specialization.
Diffusate A compound, especially a stimulatory one, which spreads through the substratum from the point of origin. See root diffusate, leachate.
Digestion The process of preparing food by chemical breakdown for absorption and assimilation.
Digestive Diverticula Intestinal caecum.
Digger Hooks Modified lip structures of the genus Diploscapter.
Digitate Finger-like in shape or divided into finger-like processes.
Digitiform Having the shape of a finger.
Digonic Female A digonic hermaphrodite. See reproduction.
Digonic Hermaphrodite A situation where sperm and ova are produced in different gonads of the same individual. See syngonic female, reproduction.

Diheteroxenous Development The requirement of a parasite for two hosts to complete its developmental cycle. See heteroxenous development, dixenous development, triheteroxenous development, trixenous development.
Dilatator Ani The dilator ani.
DilatorAni The muscle which expands the anus.
Dilator Vulvae Vulvar muscles inserted ventrolaterally in the hypodermis and functions to open the vulva. See vulvar muscles. See Figure24.
Diluent A diluting agent.
Dimorphic Individuals of the same species occurring in two distinct forms i.e. male and female. See heteromorphic, monomorphic, polymorphic, reproduction.
Dioecious Existing as separate and distinct male and female. See dimorphic, reproduction.
Dioecy A mating system involving males and females. See androdioecy, trioecy.

Diorchic Having two testes. See monorchic, reproduction.

Diovarial. See Didelphic.
Diplogasteroid Esophagus Having a muscular cylinder anteriorly followed by a median bulb, terminated by a glandular base.
Diploid Having a double (2n) number of chromosomes. See haploid.
Direct Cycle Eggs of parasitic parents hatch into free-living larvae which develop directly into parasitic forms. Homogonic cycle. See heterogonic cycle.
Direct Straight growth to maturity through four successive molts.
Disc Plate-like with a flat circular surface.
Disciform Having the shape of a plate or disc.
Discoid Having a shape like a round plate. Disk- like.
Discoloration Changed to a different color. Stained. Disease A condition produced by some factor in which any part of a ]iving organism is abnormal. See injury.
Dissemination The spread of infectious agents by any means.
Distad Toward the distal end.
Distal Remote from the point of origin or attachment. See proximal.
Distal Tubes The marginal tubes of esophageal radii. See Figure 13.
Distention The act or state of extending or stretching.
Diurnal Rhythm Having a 24 hour periodic cycle. Divergence The development of dissimilarity in forms from a common ancestor. See convergence.
Divergent Extended from a point in different directions or the trends of development.

Diversity The condition of being comprised of different types of entities, such as apecies.  Diversity is greatest when all species present are equally abundant. See abundance, true diversity.

Diversity Indices Measures or indicators of the degree of diversity. See true diversity.

Diversity-weighted Abundance A product of diversity and abundance which recognizes that both may contribute to ecosystem services.  See diversity, abundance, ecosystem services.
Diverticulum (pl. Diverticula) A blind tube or sac off from a cavity or canal. See caecum.
Divided Parted. Disunited. See partite, tripartite.
Dixenic Pertaining to the rearing of an organism with two known species of associated organisms. See gnotobiotic, agnotobiotic, xenic, axenic. synxenic, trixenic, polyxenic.
Dixenous Development. The requirement of a parasite for two hosts to complete its developmental cycle. See heteroxenous development, diheteroxanous development, triheteroxenous development, trixenous development.

DNA Deoxyribonucleic acid. A nucleic acid containing the genetic information for development and functioning of living organisms. Consists of two strands of nucleotides which have sugar and phosphate backbones.  One of four bases is attached to each sugar. The sequence of bases is copied into RNA through transcription and determines the sequence of amino acids in proteins.  See RNA.

DNA Barcoding a taxonomic method utilizing a short genetic marker in an organism's DNA, represented in barcode format, to identify the organismt as belonging to a particular speciesSee Barcode.

DNA Metabarcoding The use of barcoding to identify organisms from a sample containing DNA from an assemblage of organisms.

DNA Polymerase An enzyme that catalyzes production of DNA molecules from nucleoside triphosphates. See Polymeras Chain Reaction, PCR, RNA Polymerase.

Dormancy The dormant state.
Dormant Inactivation as if in sleep. Quiescent See aestivation.
Dorsad In the direction of the dorsum. Toward the dorsal aspect.
See ventrad.
Dorsal The back side aspect of a nematode. Belonging to the back side.
See ventral, dorsum See Figure 22,
Figure 23., Figure 28, Figure 29.
Dorsal Cord The dorsal line of the four longitudinal lines of thickening on the inner side of the hypodermis.
See cords, ventral cord, lateral cords. See Figure 21.
Dorsal Cone A prominent projection on the roof of the buccal capsule which contains the terminal orifice of the dorsal esophageal gland.
Dorsal Depressor Ani Muscle
See depressor ani.
Dorsal Esophageal Gland The dorsal most of the three esophageal glands. Note: esophagus as alternate terminiology for pharynx.
Dorsal Esophageal Gland Orifice The aperture of the duct from the dorsal esophageal gland into the lumen of the esophagus.
See esophageal glands.
See Figure 1.
Dorsal Gland Orifice The dorsal esophageal gland orifice.
Dorsal Gutter A longitudinal thickening in the in the roof of the buccal capsule which contains the terminal orifice of the dorsal esophageal gland.
Dorsal Lobe In males of some nematode forms the terminal section of the bursa lying between the dorsal rays.
Dorsal Nerve A nerve that originates from the mid-dorsal region of the nerve ring, extends posteriorly in the dorsal cord as a motor nerve devoid of, or poor in, ganglion cells.

Dorsal Pharyngeal Gland The dorsal most of the three pharyngeal glands. Note: pharynx as alternate terminiology for esophagus.
Dorsal Pharyngeal Gland Orifice The aperture of the duct from the dorsal pharyngeal gland into the lumen of the pharynx See esophageal glands. See Figure 1.
Dorsal Rays The paired genital papillae of the dorsal lobe of the bursa.
Dorsal Somatic Nerve The dorsal nerve.
Dorsolateral The position on the nematode body situated 300 laterally from the dorsomedian line and perpendicular to the anteroposterior axis Subdorsal.
See position. See Figure 22, Figure 23.
Dorsolateral Muscle Fields A segment of the dorsosubmedian muscle field being delineated by a lateral cord and a subnicdian thickening of the hypodermis.
See dorsosubmedian muscle field, ventrosubmedian muscle fields. See Figure 21.
Dorsolateral Nerves Nerves that arise between the dorsal and lateral nerves.
Dorsomedian The true middle line on the back side of an individual.
Dorsorectal Ganglion A ganglion which gives rise to a medium caudal nerve extending posteriad to the tail.
Dorsorectal Nerve A nerve that extends from the rectal commissure to the rectum.
Dorsosubmedian Muscle Fields The somatic muscle bounded by the dorsal cord and the lateral cords.
See ventrosubmedian muscle fields, subdorsal muscle fields, dorsolateral muscle fields, ventrolateral muscle fields, subventral muscle fields,
See Figure 21.
Dorsoventral An imaginary line extending from the dorsal to ventral side. The dorsoventral axis. The median line.
See position.
Dorsum (pl. Dorsa) The back.

Dorylaimoid Esophagus Having the shape of a long- necked bottle, being slender and thin at the anterior end then expanding towards the cardia.
Double Eggs Nematode ova of an abnormally large size and generally nonviable.
Double Guiding Ring A condition where the guiding sheath of the stylet has two thickened rings of cuticle.
See Figure 2.

DPGO Dorsal pharyngeal gland opening intopharyngeal lumen, the position is taxonomically important, especially in the order Tylenchida. See dorsal esophageal gland orifice, DGO, dorsal pharyngeal gland oorifice, DEGO. Note: pharynx as alternate terminiology for esophagus.
Drench To wet thoroughly especially with a  solution. To soak. To saturate.
Drench Application The treatment of soil or other material with a nematicide as a water emulsion or mixture.
See broadcast application, gas application, row application.
See guttate.
Duct A tube or channel, especially one for conveying the secretions of a gland.
See Figure 1.
Ductule A small duct.
Ductus A duct.
Ductus Ejaculatoris A duct formed by the union of the vas deferens and the duct of the seminal vesic1e for conveying the sperm to the spicula.
Ductus Masculinus The efferent duct.
Ductus Spermatic The vas deferens.
Duff The matted, partly decomposed organic surface layer of forested soils.
Dung Consuming
See coprophagous.
Dwarf Nanism
Dwarf A disease condition of plants incited by
Aphelenchoides spp. with varying degrees of deformation of stems, leaves, flowers and buds which may remain rudimentary. Often termed spring dwarf or summer dwarf.
Dwarf Plant Reduced in stature or form but retaining the same proportions as a normal plant.
See stunted plant.
Dystrophy Nutrition faulty or imperfect.

 Return to Dictionary Index


Ecdysis (pl. Ecdyses) The act of shedding the outer cuticular layer. A molt. See instar.
Eclosion The act or process of hatching from the egg.

Eco-exergy The chemical energy stored in organic matter and the genetic information embodied in biomass of living organisms, providing an indicator of ecosystem complexity and strucure. See ecosystem.
Ecology The relations between organisms and their environment. The reactions of organisms to the conditions of their existence.

Ecosystem An assemblage of living organisms interacting as a system in conjunction with each other and with their abiotic environment. 

Ecosystem Function The biological, geochemical and physical processes that take place in an ecosystem. See ecosystem services.

Ecosystem Sevices  The functions of the ecosystem, derived from the activities of living organisms in conjunction with their environment, that enable life on Planet Earth.  They may be grouped into four broad categories:  See Supporting Services, Provisioning Services, Regulating Services and Cultural Services.

Ecotone Transition areas between different communities occupied by mixed and fluctuating populations.
Ectoferment Saliva of extraoral digestion.
Ectoparasite An organism living upon and/or feeding on the host from the exterior.
See endoparasite.
Ectopore The excretory pore.
Ecumenical Worldwide in extent. General. Cosmopolitan.
Edaphic Relating to, or belonging to the soil.
See arenicolous, aquatic, hypogaeic, marine, rheophile, terrestrial, terricolous, xerophilous.
Edentate Toothless. See dentate.
Eelworm A vernacular term for any individual of the phylum Nematoda, especially for free-living and plant-parasitic forms. See nema, nematode, roundworm, threadworm.
Eelworm Disease of Hyacinth A disease condition of hyacinth incited by
Ditylenchus dipsaci.

Effective Number of Species  A measure of species diversity.  See true diversity.
Effector A molecule that selectively binds to a protein and regulates its biological activity. It may increase or decrease enxyme activity, gene expression or cell signalling.  Molecules secreted by the esophageal glands of plant-feediong nematodes that affect the development or function of plant cells are examples of effectors.

Efferent Bearing or conducting away from an organ or position. See afferent.
Efferent Duct The conveying duct of the male connecting the testis with the rectum. It is composed of the vas deferens, ductus ejaculatorius, vesicula seminalis and the distal sphincter.
Effete No longer capable of producing ova. Egg The reproductive body produced by the female. An ovum.
Egg Chamber A reservoir in the ovijector.
Egg Mass In the broad sense, the gravid female, Meloidogyne spp. with her external matrix containing extruded eggs. In the narrow sense the extruded eggs contained within the matrix. See external egg mass, internal egg mass.
Egg Sac An egg mass.
Eight-shaped (8-Shaped) Structure A panduriform structure surrounding the vestibule extension at the approximate latitude of the cephalic constriction. See lemniscate.
Ejaculatory Duct The ductus ejaculatorius.
Ellipsoidal Elliptical. Oval.
Elliptical-shaped like an ellipse. Oblong-oval.
Elongate To lengthen. To stretch out.
Elutriator An apparatus for washing soil for the extraction of nematodes. See Seinhorst apparatus.
Elutriator Apparatus An apparatus for quantitative extraction of nematodes from soil.
Embedded Buccal Capsule A condition when the buccal capsule is totally surrounded by the esophageal musculature.
Embryo An organism in the early stages of development. The organism before hatching from the egg.
Embryonated Said of an egg containing an embryo or larva. See ovic embryo, juvenile.
Embryonic Found in, or belonging to the embryo. Incipient and rudimentary.
Embryonic Development Growth and maturation of the egg.
Emend To free from a defect or a deficit.
Encyst To become enclosed in a cyst, capsule, molted cuticle or by structures which function as such. See ensheath.
End Bulb The basal bulb.
Endemic Native to a certain region. Indigenous. See exotic.
Endocuticle A section of homogenous material internal to the exocuticle. A 5-banded layer in some
Endogenous Nemin Nemin obtained from the whole of the nematode. See nemin.

Endogenous Organis Matter  Organic material providing a source of carbon and energy that is produced within a field or ecosystem. See Exogenous Organic Matter.
Endoparasite An organism living within and feeding on the host. See ectoparasite.
End Organs The nerve endings of the amphidial nerve coiled within the amphidial pouch. Fibrillar terminals.
End Organs Phagocytic structures of some coelomocytes. See terminal bodies, cellules.
Endotokia Matricida The failure of normally oviparous nematodes to deposit their eggs which may then accumulate, continue to develop, and hatch within the female body. (But see Taylor, Netscher, Chen and Caswell-Chen, 2003)
Enemy Crops A control technique where a nonhost crop is planted on Heterodera infested land. These crops produce active root diffusates induce hatching but do not support nematode development. See trap crops.
Ensate Sword-shaped. Having two edges, broad based and tapering to a point.
Ensheathed A situation where a molted cuticle remains as a protective covering investing the larva thus affording protection against adverse conditions. Encysted.
Ensiform Sword-shaped. Having two edges, broad based and tapering to a point.
Entad An inward extension from without.
Enteric Belonging to, or relating to the digestive tract or enteron.
Enteron The digestive tract as a whole.

Entomopathogenic Nematode A nematode that, either by direct feeding or by vectoring toxic bacteria, cause harm or death to an insect.
Entoparasite An internal parasite. Endoparasite.
Entrails Viscera, Internal organs.

Entropy The degree of disorder, randomness or chaos in a system, for example, aggregates of organisms in a community or food web, resulting in reduction of functions or services of the system. See Negentropy
Environment All external conditions that may act upon an organism or thing to influence its development or survival.
Epaulets Specialized, ribbon-shaped, paired bands of cephalic cuticle. See cordons.
Epiblast The outer layer of the blastoderm. See hypoblast.
Epidermal Fields The cords.
Epidermis The outer cylinder of cells consisting of a single layer of epithelium which secretes the cuticle. The hypodermis.
Epiptygma A vulval flap.

Epistrate a general term for microorganisms growing on the surface of differnt substrates, e.g.,  algae and bacteria growing on  sedimet on a river or ocean bottom.

Epistratum The upper layer.
Epizoite A sedentary nonparasitic animal living attached to another animal.
Epizootic A disease affecting many animals of the same kind simultaneously. Epidemic.

EPN Entomopathogenic nematode.
Equatorial Situated at the middle or central region of a body or part. See midbody.
Eradicate Complete destruction especially of a population.
Eructation The ejection of contents from the intestine via the mouth.

Escutcheon-shaped Having the shape of a shield. See scutate, scutiform, clypeiform.
Esophageal Bulb Any of the several enlargements of the esophageal wall, muscular or glandular. See cardiac bulb, bulbus, terminal bulb, basal bulb, true bulb, metacorpus, posterior bulb.
Esophageal Caucus A blind diverticulum at the posterior part of the esophagus.
Esophageal Collar Esophageal tissue which surrounds the stoma.
Esophageal Cuticle The cuticular lining of the esophagus lumen which differs in some respects from the external cuticle. See external cuticle, rectal cuticle, cloacal cuticle, vaginal cuticle.
Esophageal Cylinder The esophagus proper.
Esophageal Funnel A situation anterior in which the tips of the esophageal sectors are parted infundibuliformly. See infundibuliform.

Esophogeal Gland Nuclei and Orifices The position of the nuclei and orifices of the five esophageal glands of the Dorylaimina may be described in relation to the length of the esophagus:

      DO: orifice of dorsal gland (e.g. 51-55 %)

     DN: dorsal gland nucleus at center of nucleolus (e.g. 54-58 %).

     S1O: orifice of the first pair of ventrosublateral glands (e.g. 65-68%).

     S1N1: anterior nucleus of the first pair of ventrosublateral glands (e.g. 69-72 %).

     S1N2: posterior nucleus of the first pair of ventrosublateral glands (e.g. 70-74 %).

     S2O: orifice of the second pair of ventrosublateral glands (e.g. 84-86 %).

     S2N1: anterior nucleus of the second pair of ventrosublateral glands (e.g. 84-86 %).

     S2N2: posterior nucleus of the second pair of ventrosublateral glands (e.g. 88-90 %).

    K: Distance DN-S1N1 as a percentage of distance DN-S1N2.

    K': Distance DO-S1O as a percentage of DOS2O.
Esophageal Glands Elongated glands of simple or branched tubules located in the esophageal sectors, the secretions of which are apparently of an enzymatic nature, one gland being situated dorsal and two submedian or modified. See salivary glands, pharyngeal glands. See Figure 3.
Esophageal Glands Enclosed A situation where the salivary glands are contained within the esophagus body proper.
Esophageal-Intestinal Canal That segment of the esophageal lumen leading from the haustrulum through the esophageal-intestinal valve to the intestine. See Figure 15.
Esophageal-Intestinal Valve A muscular structure at the base of the esophagus opening into the intestine. See cardia. See Figure 3, Figure 15.
Esophageal Lumen The cavity bounded by the esophageal musculature serving to convey food from the stoma to the intestine. See Figure 3, Figure 13, Figure 15.
Esophageal Nerve Ring The nerve ring.
Esophageal Radii Triradiate expansion folds of the esophageal lumen which may converge terminally or become rounded to form marginal tubes. See Figure 13.
Esophageal Sectors The three sections of the esophageal musculature as divided by the esophageal radii, one dorsal and two ventrolateral See Figure 13.

Esophageal Sleeve See esophageal collar
Esophago-Intestinal Cells The esophageal-intestinal valve.
Esophago-Intestinal Junction The esophageal-intestinal value.
Esophago-Intestinal Valve Var. of esophageal-intestinal valve.
Esophagus The muscular tube that leads from the stoma or stylet base to the intestine. Alternate terminology for pharynx. The pharynx, in a strict sense since a true esophagus is lacking in Nematoda.
See Figure 1.
Esophagus Degenerate A situation where the esophageal region shows little or no evidence of its triradiate character or musculature.
Etiological Agent The parasite inciting a disease in a plant or animal.
Etiology Inquiry into the causes of a disease.

Etymology The origin and derivation of the genus and species name of an organism, or of names applied at other taxonomic levels.
Euploid Having an exact multiple of the haploid chromosome number. See aneuploid, haploid, monoploid, heteroploid, hyperploid, polyploid.
Euryhaline Capable of tolerating a wide variation of osmotic pressure in an environment. See Stenohaline.
Eurystomatous Descriptive of diplogasterid nematodes with a wide stoma, with teeth, and usually associated with predatory behavior..

Eutrophic Being in a well nourished state.
Evaginate To turn inside out or to cause an internal structure to protrude or project externally.
Eversible Capable of being turned outward or inside out. Capable of being everted.
Evert To turn inside out.
Eviscerate To disembowel. To gut.
Excrescence An appendage or outgrowth. A protuberance. See process.
Excrete To void waste products from the body.
Excretory Canal The excretory duct.
Excretory Duct A tube or canal by which the excretory products of the excretory system are conveyed to the exterior via the excretory pore.
Excretory Pore A ventral opening in the cuticle by which the waste products of the excretory system are emitted to the exterior. Cervical pore.
See Figure 1.
Excretory Sinus A common cavity of the excretory ducts communicating to the exterior by the excretory pore via a cuticle-lined reservoir or an elongated terminal duct.
Excretory System All the structures concerned in ridding the body of waste products other than the intestine.
Excurrent Attenuate. Narrowly elongated.
Exocuticle The cortical layer, fiber layer, fibrillar layer, inner matrix and boundary layer of the cuticle.

Exogenous Organis Matter  Organic material imported as a source of carbon and energy from outside a field or ecosystem. See Endogenous Organic Matter.
Exotic Introduced into the locale. Not native, See endemic.
Exsiccate To dry up. See
dehydration. desiccate.

External Amphid The cuticular manifestation of the amphid.
External Circlet The combined cephalic crown and the outer labial crown by forward migration of the former. The outer circlet.
External Cortical Layer The outermost stratum of the cuticle which is subdivisible into parts, the outer denser part and the inner less dense and thinner part. See cuticular layering.
External Cuticle The cuticle covering the exterior of the nematode body which differs in some respects from that which lines parts of the digestive tract and vagina. See esophageal cuticle, rectal cuticle, cloacal cuticle, vaginal cuticle.
External Egg Mass Eggs of Meloidogyne deposited in matrix outside the gall tissue. See egg mass, internal egg mass.
External Genital Armature The bursa.
External Parasite An ectoparasite.
External Protractor Spiculi Muscles extending posteriorly from the external side of the spicule head.
Extogenous Capable of growth outside of the body.
Extorted Turned or twisted away from the median axis. See intorted.
Extracellular Digestion Digestion of food within the intestinal cavity allowing the simpler molecules to be absorbed by the cells. See predigestion, extraoral digestion, intracellular digestion.
Extrados The exterior curve of an arch. See intrados.
Extraintestinal Digestion Extraoral digestion.
Extraoral Beyond or outside of the mouth.
Extraoral Digestion The digestion or partial digestion of food outside of the body (for instance, the salivary injection into cell protoplasm prior to ingestion). See predigestion, extracellular digestion, intracellular digestion.
Extrorse Turned or facing outwards. Toward the outside. See introrse.
Eye Spots Structures present in some freshwater and marine nematodes which consist of a lenticular cuticular body situated on a pigment cup.

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F1 The first-generation offspring resulting from a given mating. F2 the second generation, etc.
Facultative Aerobic Capable of living without the presence of atmospheric oxygen, though capable of utilizing it when available.
Facultative Anaerobic Normally living in the presence of atmospheric oxygen, but capable of becoming anaerobic. See aerobic, anaerobic, facultative aerobic, obligatory aerobic, obligatory anaerobic.
Facultative Parasite Organisms ordinarily saprophytic or saprozoic which may become parasitic under certain conditions. See obligate parasite, facultative saprophyte.
Facultative Saprophyte Organisms ordinarily parasitic which may subsist as saprophytes during part of their life cycle but do not complete their cycle away from a host. See facultative parasite, obligate parasite, obligate saprophyte.

Fahrenholz's rule (1913) .When host-parasite cospeciation has occurred, the phylogenies of the host and parasite come to mirror each other.  However, often phylogenies are altered by host switching, extinction, independent speciation, and other ecological events so cospeciestion may be difficult to detect.  See cospeciation, phylogeny.
Falcate Curved like a sickle.
Falciform Having the shape of a scythe or sickle.
Fallow Cropland left idle in order to restore productivity, mainly through accumulation of water, nutrients, attrition of pathogens; probably a combination of these.
Family In the systematic arrangement of organisms into groups or categories denoting natural relationships a category ranking above a genus and below an order. See classification.
Fascicle A bundle. A cluster.
Fat Body A trophosome.
Faulted The interruption then continuance of a line parallel to the original but on a different plane.
Fauna Animals or animal life. See flora, biota.

Faunal Analysis  Assessment of the relative proportions of nematodes of different feeding habits and life history characteristics to provide inference of the state of the soil ecosystem and its potential for providing Ecosystem Services.
Fecundation Fertilization, as of eggs by spermatozoa.

Fecundity The abundance of offspring produced by a female or the rate of offspring production.
Feeding The intake of substances essential to growth, sustenance and maintenance of an organism. See
bacteriophagous, bacterivore, biophagous, carnivorous, coprophagous, cycophagous, detritophagous, fungivore, fungivorous, herbivorous, lancinate, microbivorous, microphagus, monophagous, mycohelminths, mycophagous. nematophagous, oligophagous, ominivorous, parenteral feeding, phyllophagous, phytophagous, polyphagia, polyphagous, polyphagy, predaceous, predator, rapacious, rypophagous, saprobiont, saprophage, saprophagous, saprophyte, saprozoic, saprozoite, sarcophagous, scavenger, voracious.

Female Gangs The female genitalia.
Female Genital Aperture The vulva.
Female Intersex An individual which begins development as a female but finishes development as a male. See intersex, male intersex.
Fenestra (pl. Fenestrae) A window. A transparent spot. In the genus Heterodera a thin walled transparent region of the vulval cone which may breakdown to form the hatching pore. The thin- walled region about the anus in some Heterodera. See fenestrate, semifenestrate, bifenestrate, ambifenestrate, circumfenestrate, vulval fenestra, anal fenestra. Also, and opening through which a nerve passes. See Figure 30, Figure 31, Figure 32, Figure 34.
Fenestration The process of forming the hatching pore by the breakdown of the thin areas of cuticle of the anal or vulval cone.

Ferment Saliva.

Fertilization Membrane The lipoid membrane.
Fiber Cells Modifications of the hypodermis which contributes to the formation of the lips, two in the dorsal lips and one in the lateral and ventral lips.
Fiber Layers Three cuticular strata of dense connective tissue which is oblique, ribbon-ike, possibly spiral and delimited by the boundary layer and the basal lamella. See cuticular layering.
Fibril (pl. Fibrillae) The fibers which constitute the actual contractile substance of the muscle cell.
Fibril Cells Three coelomocytic cells which lie adjacent to the esophagus and opposite the three esophageal radii. See coelomocytes, binding cells.
Fibrillae Thread or fiber-like supporting structures of the hypodermis.
Fibrillar Layer The cuticular stratum consisting of a condensation of spongy matrix forming a closely woven network between the internal cortical layer and the matrix layer. See cuticular layering.
Fibrillar Terminals The nerve endings of the amphidial nerve coiled within the amphidial pouch. End organs.
Fibroplasm That portion of the muscle cell differentiated into muscle fibers. See sarcoplasm. See Figure 8,
Figure 9.
Fibrous Root System Adventitious roots which arise from the base of the stem, bulb or corm. See Lap root system.
Field Capacity The amount of moisture remaining in a soil after the free water has been allowed to drain away into drier soil material beneath; usually expressed as a percentage of the oven dried weight of soil. It is the highest amount of moisture that the soil will hold under conditions of free drainage after excess water has drained away following rain or irrigation.
Filament A slender, thread-like object, process or appendage.

Filaria(ae) See Filarial Nematode

Filarial Nematode or Filarial Worm  Any of a group of animal-parasitic nematodes that require two hosts to complete the life cycle, an intermediate host (often an arthropd) and a primary host (usually a vertebrate). The juvenile stages occur in the intermediate host and the reproductive adult in the definitive (primary) host. Transmission occurs by the intermediate host biting the primary host or the intermediate host being eaten by the primary host.  Inflammation of the definitive host tissues is called Filariasis.  See Filariasis

Filarial Worm Systematics Nematodes of the families Filariidae, Onchocercidae and other taxa of similar biology, Historically, filariae referred to  genera of nematodes in the Filariidae. However, when the family Onchocercidae was established, many of the genera previously considered to be filarial worms in the Filariidae were transferred to Onchocercidae.and other taxa of similar biology.

Filariasis A disease of a primary host cause by filarial nematodes. Eight species of filarial nematodes have humans as the definitive host. They can be divided into three groups:

a) Lymphatic filariasis is caused by nematodes occupying and disrupting the lymphatic system, often resulting in significant swelling of tissues and elephantiasis.  Nematode species in this group include Wuchereria bancrofti, Brugia malayi, and Brugia timori.

b) Subcutaneous filariasis is caused by nematodes occupying the subcuatneous layers of the skin, including the eye.  Species in this group include Loa loa and Onchocerca volvulus which causes river blindness.

c) Serous cavity filariasis is caused by nematodes occupying mesothelial tissues in the body cavity of the host.  They include Mansonella perstans and Mansonella ozzardi in the host abdomen and Dirofilaria immitis in the heart of dogs.

Filiation Descent from a parent. Lineage.
Filiform Having the shape of a thread or filament.
Filling Cells The cells of the lip pulp other than the clavate cells, fiber cells or arcade cells.
Fimbriate Fringed.
Final Host The definitive host.
Finger-like See digitate.
First Bulb The metacorpus.
Fissiparous The production of individuals by fission. See reproduction.

Fissura Cephalica Head cleft.
Fissure A cleft or groove separating adjacent tissues, parts or organs.

Fitness The level of adaptation of an individual or species to existing environmental conditions resulting in survival and reproductive success
Fix To ha
rden and preserve relaxed specimens especially for permanent mounting and microscopic study.
Fixative Generally a mixture of chemicals which harden and preserve the bodies of relaxed specimen s.
Fixed Athrocytes Stationary coelomocytes capable of absorbing foreign material from the body fluids and storing it in crystalline form. See coelomocyte.
Flaccid Limp. Feeble. Limber.
Flabellum. Fan- or feather-shaped dorsal or ventral extensions of the cuticle.

Flagellum In differential staining of mermithid larvae bodies with carmalum, the posterior region stains very light and is termed "flagellum."
Flange A rib, rim or expansion developed for strength, guiding or attachment to another part or organ. See Figure 4.
Flap Apparatus The valvular apparatus.

Flask-shaped See ampullate, ampulliform, lageniform.
Flavate Bodies Where present, four elongate, yellowish, gland-like structures situated submedianly near the base of the stylet.
Flesh Consuming See biophagous, carnivorous, feeding.
Flooding A control measure against plant parasitic nematodes where soil is kept saturated or submerged.
Flora Plants or plant life. See fauna, biota.

Flush The development of a generation of nematodes.

Flushing Glands Secretion supplying glands of the amphids and plasmids

Focus (pl. Foci) A localized region of disease or the principal site of a general disease.

Foregut The esophageal region of the alimentary tract. See midgut, hindgut.

Forked See furcate, trichotomous, tricuspid, tricuspidate, tridentate, trifid, trifurcate.

Fornent In an opposite position. Facing. See apposition, juxtaposition.

Fossa A ditch-like depression.

Fossorial Equipped for, or capable of digging.

Framework A cephalic structure which provides rigidity to the head. It is subcuticular and axially forms a stylet guide in stylet-bearing forms. See calvarium.

Fovea A pit or depression, a small fossa.

Frass Solid excrement of larval insects.

Free-living Living independently of any host organism. A nonparasite. See parasite.

French Bud A disease of strawberry incited by Aphelenchoides fragariae. See dwarf.

Frenching A disease of strawberry incited by Aphelenchoides fragariae. See dwarf.

Fringe An edging of processes extending beyond the margin and are usually of equal length. See fimbriate.

Frontal Disc The labial disc.

Frustule The hard and porous external silicaceous layer of diatoms; sometimes seen in intestines of free-living nematodes and considered an indicator of feeding sources.

Fumigant Nematicide A nematicidal chemical with high volatility that moves through the soil primarily in the gaseous phase.

Functional Group A group of species that contribute to the same ecosystem function.

Functional Guild  Subsets of a Functional Group with similar general biology, structure or behavioral adaptations.  See Functional Group; Trophic Guild..

Fungivorous Feeding on fungus mycelium. See feeding.

Fungivores Organisms that feed on fungi.

Fungus (pl. Fungi) A low form of plant life which lacking chlorophyll and being incapable of manufacturing its own food, lives off dead or living plant or animal matter. The body of a fungus consists of delicate threads (hyphae) which in mass form branched systems called mycelia.

Funnel-shaped See infundibuliform.

Funnel Technique See Baermann funnel technique.

Furca The branched distal part of a probola.

Furcate Forked. Having two divergent branches with a common base.

Fusiform Spindle-shaped. Tapering toward each end.

 Return to Dictionary Index


Gall A pronounced localized swelling. An outgrowth of unorganized cells generally more or less spherical or fusiform.
Gallery A passage or tunnel made by an animal.
Galvanotaxis A tactic response in which an electric potential is the stimulus. See Taxis.
Gamete A mature reproductive cell. See spermatozoon, ovum.
Gametogenesis The development or formation of reproductive cells.
Gamogonic Pertaining to sexual reproduction.
Ganglion (pl. Ganglia) A well defined concentration of nerve cell bodies forming a nerve center.
Gas Application The treatment of soil or other material with a nematicide in a vapor phase. See broadcast application, drench application, row application.
Gaseous Aeriform.
Gastrula The early embryo, consisting of an open mouthed sac-like body with a wall of two layers of cells, an outer epiblast and an inner hypoblast. The opening is called the blastopore and the central cavity the archenteron. See blastula.
Gavage Introducing contents into the stomach by means of a tube.
Gene The basic unit of heredity in a living organism. A segment of genomic information encoded by DNA that specifies a trait. See DNA..

Gene-for-Gene A hypothesis proposed by Flor that for each gene conditioning a reaction in a host, there is a corresponding gene in the pathogen that codes for pathogenicity. See gene.

Generalist Predators Nematodes that feed on other living organisms but not necessarily restricted to a single type iof prey. See specialist predators.

Generation A single set of progeny in the succession of natural descent. The period of time in which one set of progeny follows another. See life cycle..

Geniculate Bent to an obtuse angle.
Genital Aperture The vulva in females, The anus leading to a cloaca in males.
Genital Armature All the apparatus involved in copulation.
Genital Cone A posterior projection of the region around the cloacal orifice. The cloacal prominence.
Genital Organs The reproductive organs. See ovary, testis.
Genital Papillae (GP) Tactile papillae or setae in the anal region of the male and may be preanal, postanal or caudal in position. See pedunculated papillae, rosettes, plectanes, copulatory warts, preanal sucker.
Genital Primordium The initial cells leading to the development of the reproductive system.
Genital Setae See genital papillae.
Genital Tract The gonads.
Genital Tubes The gonads.
Genitalia The organs of generation. In the male these consist of the testis, seminal glands with their ducts, gubernaculum and spicule. In the female the vulva, vagina, ovary, oviduct, seminal receptacle and uterus.
Genoholotype A genotype specifically named as generic type by the author. See type.
The type of a genus selected from a series of species placed in the genus after the description. See type.

Genome The complete set of genes or genetic material in a cell.

Genomics Study of the structure, function, evolution and mapping of genomes.

Genosyntype One of a series of species upon which a genus is based with no one species having been established as type. See type.
Genotype The species which is designated as the type species of a genus. See type.
Genotype The total genetic makeup of an individual or group. See phenotype.
Genus (pl. Genera) In the systematic arrangement of organisms into groups or categories denoting natural relationships a category ranking above a species and below a family. In binominal nomenclature the first word of the scientific name of a species is the generic name and is capitalized. The second term is the trivial name and is not capitalized. See classification.
Geographical Distribution The inhabited range of a species.
Geotaxis A tactic response in which gravitational attraction is the stimulating factor. See taxis, tropism.
Geotropism A tropic response in which gravitational attraction is the orienting factor. See tropism, taxis.
Germarium The germinal zone.

Germ Layers The layers of cells that are distinguishable in the embryo immediately after gastrulation.  In most animals, the layers give rise to similar tissues and organs.  Diploblastic animals, such as Coelenterata, have two layers, ectoderm and endoderm.  The ectoderm gives rise to external structures and the endoderm to internal structures such as intestine and reproductive organs. Triploblastic animals have a third layer, mesoderm, which gives rise to muscle and skeletal structures and which surrounds the body cavity.

Germinal Zone That part the ovary where the oogonia divide. See growth zone.
Giant Cells A structure formed most commonly in root tissue by the coalescing of several cells through dissolution of common walls under stimulation of salivary secretion by gall-forming nematodes and some other kinds. Lysigenoma. See hypertrophy, hyperplasia, nurse cell.

Gland Nuclei and Orifices See Esophogeal Gland Nuclei and Orifices.
Gland-like Adeniform.
Glandular Esophagus A ventricular esophagus.
Gliding Ring The guiding ring of the stylet. See guiding ring of stylet, Figure 2.
Globate Spherical.
Globular Globe-shaped. Spherical.
Glottoid Apparatus The metastom of Rhabditids and Diplogasterids formed of one dorsal and two subventral metarhabdions. See isoglottid, isomorphic. Figure 40

Glottoid Part Distinct regions of the stoma consisting of one dorsal and two subventral pieces that may be of different shape (anisomorphic) or in different positions (anisotopic). May bear denticles or teeth.
Glottoid Teeth Metarhabdion projections of the glottoid apparatus.
Glucoprotein A segregate of the cuticle (a mucoid).
Glucosamine The chief constituent of chitin.
Glucose A simple 6-carbon sugar.
Glycogen Animal starch. A soluble polysaccharide made up of numerous glucose molecules. The form in which carbohydrates are stored in the animal. Helminth glycogen is a mixture of compounds varying considerably in molecular weight.

Gnathi Jaws.
Gnotobiotic Pertaining to the rearing of an organism with no other or only known species of associate organisms. See Agnotobiotic, axenic, xenic, synxenic, monoxenic, dixenic, trixenic, polyxenic.
Gonad A primary sex gland. An ovary or testis.
Gonochoristic Sexually reproducing species in which there are at least two distinct sexes. The sex of an individual is genetically determined and does not change throughout its lifetime.

Gonochorism Sexual reproduction involving two distinct sexes.
Gonoduct A reproductive tube. A gonad.
Gonopore The opening to the exterior of the gonads; the vulva in the female and the anus in the male.
GP See genital papillae

Gradual Metamorphosis Incomplete metamorphosis.

Granek's Ratio In Heteroderidae, the distance from the edge of the fenesta to the anus divided by thelength of the fenestra.
Grape Cluster-like See aciniform, botryoid.
Gravid Bearing an egg or eggs.
Gravity Flow System A method of applying liquid nematicides to soil utilizing liquid head, liquid viscosity, tubing diameter and tractor speed for regulating the rate of application.

Grinder Cuticular Plates in the posterior bulb of the esophagus of many bacterial-feeding nematodes.  Have the function of crushing bacteria prior to digestion in the intestine. See chewing plates, valve plates, Figure 40
Grouped See agminate, aggregated.
Growth Zone That part of the ovary where the oogonia develop. See germinal zone.

Guard Process One or two cuticular projections at the base of a primary axil. See primary axil, Figure 36.
Gubernacular Muscles Specialized muscles for the functioning of the gubernaculum. See retractor gubernaculi, protractor gubernaculi, seductor gubernaculi.
Gubernaculum In male nematodes a grooved cuticularized structure, sometimes paired, which guides the spicule and is formed by sclerotization of the dorsal wall of the spicular
pouch. See cuff, crura. See Figure 5, Figure 14, Figure 16, Figure 41.
Guide Collar The guiding ring of the stylet.
Guide Ring The guiding ring of the stylet.
Guiding Ring of Stylet The anterior end of a guiding sheath of the stylet cuticularized or muscular thus appearing to be more dense than surrounding tissue. See guiding tube of stylet. See Figure 2.
Guiding Tube of Stylet A sheath about the stylet extending from the "guiding ring" to the stylet
base. See Figure 4,  Figure 6.

Guild A group of species with similar behavior, life history characteristics or ecosystem function.  See functional guild, structural guild.
Gut The intestine.
Guttate Drop-like.
Guttiform Having the shape of a drop. Drop-like in form.
Gynandromorph An individual in which the secondary male and female characters are present in the same individual but different parts of the body, sometimes an hermaphrodite but not necessarily so, See intersex, reproduction.

Gyne An unmated adult female bumblebee that returns to the overwinter burrow and becomes infected by parasitic nematodes such as Sphaerularia bombi, or disperses juveniles of the nematode.

Gynodioecious Descriptive of a population expressing the characteristics of gynodioecy.

Gynodioecy The condition in which a population comprises both females and hermaphrodites.

Gynogenesis The process by which progeny are developed solely from the maternal genome; i.e. sperm DNA is not utilized. See Parthenogenesis.

Gynotype A female type. See type.

 Return to Dictionary Index


Habitat The natural environment of an organism, specifically, the locale in which it grows and lives.
Haemolymph The watery lymph-like nutritive fluid of the nematode pseudocoel.
Hairy See piliferous, trichoid.
Hairy Root A condition of excessive root branching induced by nematode feeding.
Half Turned See hemitrope.
Halophilous, Halophilic Living in a salty environment.
A form of symbiosis in which two species live in association without obvious motive or advantage to either symbiont.
Hamate Having a hook or hook-shaped. See adunc.
Hand-shaped See palmate.
Haploid Single in appearance or arrangement. Having the basic (n) number of chromosomes for the species. See diploid.

Haplotype A set of alleles (DNA variants) along a single chromosome that tend to be inherited together. Because of their proximituy on the chromosome, recombination amongst these alleles is rare. See genotype, allele.
Hard Cuticle The material that builds up the jaws teeth, cuticular lining of the oral cavity and the male genital armature. It has consistency of chitin. See soft cuticle.
Hatching The breaking of the egg shell by a larva during the process of emergence. Eclosion. See spontaneous hatching.
Hatching Factor An external hatching stimulus which acts on eggs. See root diffusate, leachate.
Hatching Pore The fenestra.
Hatch Plant A host plant capable of inducing larval emergence from eggs.
Haustrulum Cuticularized chamber(s) posterior to metacorpus valve.grinder/pump. See Figure 15, Figure 40.
Head Bristles
The cephalic crown of papillae or setae.
Head Bulb Specialized cuticular inflations which form a band-likc structure immediately posterior to the lips. See ballonets.
Head Cap A distinctively set off head region.
Head Cleft A pouch-like cephalic sensory organ, lateral in position, which possesses, in comparison with the amphids, a simpler innervation. Also termed cephalic organ, organe cephalique, fissura cephalica.
Head Offset Head region delimited by a depression or a constriction.
Head Shields Cuticular collar extensions that arch over the lips, considered interlabia by some authors.
Heautotype A specimen indentified by the author as an illustration of his species and compared with the type or cotype. Autotype. See type.
Hectare A. unit of land area equivalent to 2.471 acres.
Helix Having a spiral form.
Helmet A thickening in the labial region set off by a groove and denoted by a lack of ornamentation of the anterior cuticle. See cane.
Helminth A worm.
Helminthiasis A disease incited by worms in or on a host.

Helminthic Relating to, or belonging to, worms.

Helminthology The branch of zoology dealing with worms, especially parasitic worms.

Hemi-rosette An optical-dense semicircular structure with corrugated arch edging connecting the uteri of some frehwater free-living nematodes.

Hemispheroid Having the shape of half a globe or sphere. Semiglobose.

Hemitrope Half turned around. Half inverted.

Hemizonid A nerve commissure of a highly refractive nature, generally biconvex in longitudinal section and which extends ventrally from lateral cord to lateral cord. See cephalids, hemizonion, caudalid, parahemiizonid. See Figure 1, Figure 4.
Hemizonion A small nerve commissure with many characteristics of the hemizonid and apparently always shortly posterior to the hemizonid. See cephalids, hemizonid, caudalid, hemi
. See Figure 1, Figure 4.
Herbivores Organisms that derive their sustenance entirely from vegetable matter. See feeding.
Herbivorous Feeding on vegetable matter. See feeding.
Heredity Transmission of genetic characters of parents to their progeny.
Hermaphrodite An individual with both functional male and female reproductive organs. See protandrous hermaphroditism, digonic hermaphrodite, syngonic hermaphrodite, intersex. gyandromorph, androgynous, reproduction.
Heterogeneous Differing in kind, qualities or nature. See homogeneous.
Heterogenetic Development where the larvae do not resemble the parents. See monogenetic reproduction.
Heterogonic Cycle A situation where eggs of parasitic parents develop into free-living males and females, their progeny then proceed to the parasitic phase. Indirect cycle. See homogonic cycle.
Heterogony Alternation of two sexual generations or of a sexual and a hermaphroditic generation. See reproduction.
Heterology The lack of similarity between structures from being composed of different components or of a different derivation, See anology, homology.
Heterolysis Destruction of a cell by an external agent, especially, by lysins or enzymes from an outside source. See autolysis.
Heteromorphic Having different forms at different life stages. See dimorphic, monomorphic. polymorphic.
Heteroploid Having a greater or smaller chromosome number than the diploid number but not a simple multiple of the haploid chromosome number. See monoploid, aneupolid, euploid. hyperploid, polyploid.

Heterotroph An organis that depends on another organism, living or dead, as a source of food and energy,  See Autotroph

Heteroxenous Development Development of a parasite that requires two or more host species. See diheteroxenous, dixenous, triheteroxenous, trixenous.
Heteroxeny See Hetoxenous Development.

Hexamerous Having six radially-arranged parts or structures.
Hexebesen A witches broom condition on a plant.
Hiatus A natural opening in the egg shell. See plug. May also refer to a space or gap in a sequential arrangement of structures such as supplements.
Hibernation The anabiotic state. See anabiosis

Hill Application Spot application of a nematicide.
Hindgut The rectum. See foregut, midgut.
Hispid Rough with minute spines.
Hispidulous Minutely hispid.

Historopic Attracted towards tissues.

Holapopmorphy A situation where two species descended from the same ancestor share the same "innovative" or recent apomorphic trait See apomorphy, synapomorphy, plesiomorphy, autapomorphy.
Holarctic Realm A faunal area comprising Europe North Africa, to the Sahara desert, Asia to the Himalaya Mountains and the North American continent down to Mexico. See Nearctic region.
Holidic Pertaining to a medium whose intended constituents, other than purified inert materials, have exactly known chemical structures before compounding. See meridic, oligidic.
Hologonia A gonad where proliferation of primordial germ cells extend along its entire length.
Hologonic Gonads See hologonia.
Holomyrian A situation where the longitudinal muscle cells are indistinguishable as individual cells especially as viewed in transverse section. See meromyarian, polymarian.
Holotype The individual specimen selected as type of a species by the author. See type.
Homogeneous Similar in kind, qualities or nature. See heterogeneous.
Homogenous Layer The matrix layer of the cuticle.
Homogonic Cycle
A situation where eggs of parasitic parents hatch into free-living larvae which develop directly into parasitic forms. Direct cycle. See heterogonic cycle.
Homologue A part or organ of the same relative structure, position or origin as another. The same in different individuals varying in form and function. See analogue.
Homologous Similarity of structure, but independent of function, See analogous.
Homology Structure of fundamental similarity, but independent in function, derived from descendence through some common ancestral form. See heterology.
Homonym A generic or specific name already occupied and therefore rejected due to the law of priority which requires the use of the earliest published name. Two or more entities having the same name.
Homotype A specimen compared with the type and determined to be conspecific with the type. See type.
Honeycombed See alveolate.
Hook-like See adunc, hamate, unciform, uncinate. Horn-shaped See bicorn, corniform.

Horizontal Gene Transfer (HGT)  The transfer of genetic material between organisms in a manner other than sexual or asexual reproduction, e.g. by transformation or viral infection.  See vetrical gene transfer.
Horizontal Resistance Resistance to races or biotypes of the nematode species is uniform, not race specific - reduces selection pressure
. Usually controlled by several genes. See resistance.

Host The organism which is invaded or parasitized by a disease-producing agent and from which the parasite obtains its sustenance. See host range, suscept.
Host List The range of organisms infected by a specific parasite. See host range.
Host Plant The plant which affords sustenance to a nematode parasite and allows reproduction.

Host Preference The selection of a host most suitable for the survival of the parasite.
Race Nematodes of the same species differing only in their preference of host plants. See race, physiologic race.

Host Range The number of organisms parasitized by a specific nematode. See host list, stenoxenous.
Host Selection The food preferences of parasitic nematodes.
Hot water Treatment The steeping of bulbs, seeds and other plant parts in a water bath at a temperature lethal to the infecting nematodes and leaving the plant material undamaged.
Humidity The weight of water vapor in a given quantity of air, compared with the total weight of water vapor which the air is capable of holding at a given temperature.
Humus The well decomposed organic matter in mineral soils.
Hyaline Clear. Transparent. Without color. Glassy.
Hydrogen-ion Concentration A measure of the acidity of a chemical in solution. The greater the concentration of hydrogen ions, the more acid the substrate. The hydrogen-ion concentration is expressed in terms of the pH of the substrate. See pH.
Hydrolysis A chemical decomposition process of a compound which involves the addition of the elements of water.
Hydrotaxis A taxis in which a moisture gradient is the response initiating stimulus.
Hygroscopic Readily absorbing and retaining moisture.
Hyperparasitism A situation where parasites in turn are parasitized by other organisms.
Hyperplasia The abnormal increase in the number of cells of a tissue. See hypertrophy.
Hyperploid Having a chromosome number slightly greater than an exact multiple of the haploid number. See monoploid, euploid, aneuploid, heteroploid, hyperploid, polyploid.
Hypersensitive A violent reaction to parasitic attack resulting in sudden death of invaded tissues providing a barrier against further invasion.
Hypertonic A solution having an osmotic pressure higher than an isotonic fluid such that it gains water by osmosis across a membrane. See isotonic, hypotonic.
Hypertrophy The abnormal enlargement of cells generally by dissolution of common cell walls. See hyperplasia.
Hypha (pl. Hyphae) One of the thread-like strands, or filaments, that constitute the body or mycelium of a fungus. It may be divided into cells by cross walls, a septate condition, or be one elongated cell with several nuclei, a nonseptate or coenocytic condition. The hypha may be coarse or fine, aerial or submerged, stiff or flexible and exhibit different types of branclung. Some hyphae are specialized for producing spores or for penetrating host tissue.
Hypoblast The inner layer of the blastoderm. See epiblast.
Hypodermis A thin cell layer beneath the cuticle with longitudinal thickenings protruding between the longitudinal muscles to form the cords which contain the nuclei of the hypodermal cells, See lateral cord, ventral cord, dorsal cord.
See Figure 21.
Hypogaeic Subterranean. Living underground. See arenicolous, aquatic, edaphic, marine, rheophile, terrestrial, terricolous, xerophilous.
Hypothesis (pl. Hypotheses) A tentative explanation of a phenomenon. See postulate, theory.
Hypotonic A solution having an osmotic pressure lower than an isotonic fluid such that it loses water by osmosis across a membrane. See isotonic, hypertonic.
Hypotygma Papilla-like processes on cloacal aperture of male.

Hypotype A specimen, other than the type, upon which a subsequent or emended description or figure is based. Apotype. Plesiotype. See type.


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Ideotype A specimen named after comparison with the type, to be distinguished from a topotype. See type.
Imbricate Arranged or appearing lapped over one another like shingles on a roof.
Imbrication An overlapping of the edges as of tiles or shingles.
Immature Not yet at the state of full sexual development.
Immobile Larva The development of the male of cyst-forming nematodes within the cuticle of the third stage larva.
Immunity The ability of an organism to remain free from a disease or of parasitism by virtue of inherent properties of that organism. An immune organism is exempt from the-particular disease. See tolerant, resistant.
Impermeable Not permitting passage. Impervious.
Impregnation The act of rendering pregnant. Fecundation.
Incisures See involutions.

Incompatible Host-Parasite Relationship Interaction between a nematode species and host plant that is unfavorable for nematode survival and reproduction.  See compatible.
Incomplete Metamorphosis A growth phenomenon where young through successive stages, or instars acquire adult characteristics which become functional at maturity. See complete metamorphosis.
Increase Factors The several formulae used to calculate the gain in population of cyst-forming nematodes as follows:

Increase factor X1 = (total cysts obtained at season's end)/(original number of cysts)
Increase factor X2 = (number new cysts produce at season's end)/(original number of cysts)
Increase factor X3 = (total eggs obtained at season's end)/(original number of eggs)
Increase factor X4 =
(number new eggs produced at season's end)/(original number of eggs)

Incubation The period of time and conditions of environment between inoculation of an organism by a disease-producing agent and the appearance of symptoms.
Indentate Having an irregular margin. See serrate.
Indicator Plant A suitable suscept plant used to signify the survival or reproduction of plant-parasitic nematodes after some treatment or condition of population stress.
Indigenous Living in its natural or original locality. Native. See endemic.
Indirect Cycle Eggs of parasitic parents develop into free-living males and females, the offspring then proceed to the parasitic phase. Heterogonic cycle. See homogonic cycle.
Indirect Development Complete metamorphosis.

Indomalayan Realm The biogeographic region that includes the Indian subcontinent and southeast Asia.  See Holarctic Realm. Neotropical Realm, Afrotropical Realm, Australasiian Realm.
Infect To invade and establish a parasitic relationship within the host proper. See infest.
Infection Incidence The population density of attacking parasitic nematodes.
Infectious Larvae Infective larvae.
Infective Having the qualities necessary to enter a host and produce a disease condition.
Infective Larvae Nematode larva at a stage of development capable of penetrating and infecting a host.
Infective Juveniles Infective larvae.
Infective Stage The period of development in the life cycle of a parasitic nematode in which it possesses the qualities enabling infection of a host.
Infective State The infective stage.
Infest To attack externally. To contain the parasites, said of nonliving material. See infect.
Inflated Annules Enlarged annules often with a lumen or other modification of an intra-annule cavity.
Inflation of the Cuticle A blister-like swelling of the cuticle.
Inflect To curve or bend inwards or towards the axis. See infiexed.
Inflexed Curved, bent or directed abruptly inward, downward or toward the body axis. See inflect.
Infraspecific Included within a species. See con- specific.
Infundibuliform Funnel-shaped.

Ingest To take substances, especially food, into the body.

Inhalation LC50 The concentration of a chemical at which 50% of the target organisms are killed when the chemical is inhaled; for example, 10 mg of chemical per liter of air. See lethal concentration.
Injury Damage of relatively short duration to an organism. See disease.
Inlet Valve The esophageal lumen just anterior to the valvular apparatus and opening into the haustrulum. -
Inner Body The inner mass
Inner Circlet The crown of inner labial papillae. The internal circlet. See outer circlet: See Figure 2,
Figure 22, Figure 23..
Inner Cuticular Layer This layer corresponds to the fiber layers of the cuticle. See Figure 21.
Inner Labial Situated on that part of the lips located closest to the longitudinal axis. See inter labial, outer labial.
Inner Labial Bristles Inner labial papillae which have been altered to bristle-like structures.
Inner Labial Papillae Sensory papillae situated toward the apex of the lip segment forming a circlet of six in primitive forms. See outer labial papillae. See
Figure 22, Figure 23..
Inner Leaf Crown An amplification of the corona radiata by the formation of a second more posterior crown of lobes. See Figure 12.
Inner Mass A darkly staining structure slightly post-equatorial in microfilariae.
Inner Membrane The lipoid membrane.
Innervation The nerve distribution to or in a part or organ.
Inoculate To cause an infectious agent (the maculum) to come in contact with a host.
Inoculant Inoculum.
Inoculation The communication of an infective agent to the host to cause a disease.
Inoculum The infectious agent used in inciting a disease.
Inorganic Substances occurring as minerals in nature or obtainable from them by chemical means. All matter except the compounds of carbon, but including carbonates, Inanimate. See organic,
Inseminate To introduce spermatozoa into the vagina of female nematodes.
Insemination The introduction of semen into the female reproductive tract. See copulation.
Instar The nematode larval condition of growth assumed between successive molts. See molt, ecdysis, larval stages, stadium.
Integument Cuticle. Covering. Investment. Skin.
Intercallary Additional. Interpolated. Inserted between.
Intercordal Areas The nonthickened regions of hypodermis devoid of nuclei lying between the cords. See cords.
See Figure 21.

Interface The common surfaces of two bodies.
Interior Mass Inner mass.
Interkinesis The interval between mitoses of a nucleus.
Interlabia Small lobes situated between the lips.
Interlabial Situated between the lips. See inner labial.
Interlabial Clefts The space or fissure separating the lips.
Intermediate Host The host in which the asexual stages of a parasitic life cycle take place.
Intermediate Striae The lesser lines situated between the major configuration lines of a perineal pattern. See partial striae, lighter striae, broken striae.
Internal Circlet The crown of inner labial papillae. The inner circlet.
Internal Cortical Layer The cuticular stratum bounded by the external cortical layer on the outer most side and the fibrillar layer on the inner side. See cuticular layering.
Internal Egg Mass Eggs of Meloidogyne spp. deposited in matrix within the gall tissue. See egg mass, external egg mass.
Internal Parasite Endoparasite.
Interphasmidal Line An imaginary line connecting the phasmids in a Meloidogyne perineal pattern. See
Figure 28, Figure 29.
Intersex An individual which exhibits a blending of male and female characters and which function as one or the other or neither sex, but never as both. See
gyandromorph, male intersex, female intersex.

Interstitial The space between grains of sand on a beach, river bank or estuary.
Interstrial Region The area between two striae.
Intestinal Caecum A blind diverticulum arising at the anterior of the intestine and extending anteriorly next to the esophagus.
Intestinal Tract The alimentary canal. See Gut. See Figure 3.
Intestine A simple tube, composed of a single layer of epithelial cells in which digestion of food takes place. Gut.
See Figure 1, Figure 18.
Intestino-Rectal Sphincter The valve of intestinal tissue separating the intestine from the rectum or cloaca.
Intestino-Rectal Valve The intestino-rectal sphincter.
Intima An internal lining.
Intima of the Esophagus A cuticularized tube of triradiate form circumscribing the lumen of the esophagus.
Intorted Turned or twisted inward. See extorted.,
Intracellular Occurring or situated within a cell.
Intracellular Digestion The digestion of food particles within the cell. See extra-oral digestion, predigestion, extracellular digestion.
Intrados The interior curve of an arch. See extrados.
Intraoral Within the mouth.

Intrauterine Within the uterus.
Intrauterine Generations The development of mature males and females within the uterus of the mother; then yet another generation may develop within the progeny.
Intravial Stain See intra vitam.
Introduced Species See adventive.
Introrse Facing or directed inward, See extrorse.
Invalivate To mix with saliva.
Invasion Growth or movement of an infectious agent into a host with its subsequent establishment as a disease. See attack, infective.
Invasive Larvae Infective larvae.

Ivermectin Anthelminthic and insecticide chemically derived from avermectins. See avermectin, abermectin
Invertebrate Without a backbone or vertebral column. 
Involutions The longitudinal cuticular clefts which divide the lateral fields. Incisures. See Figure 17,
Figure 19, Figure 21.
Ion An atom or molecule bearing an electrical charge. See anion, cation.
Isoglottid Having the metarhabdions of the glottoid apparatus at the same level, See anisoglottid.
Isolation Tissue The pseudocoelomic membranes and mesenteries.
Isomorphic Of identical or like form especially pertaining to the metarhabdions of the glottoid apparatus See anisomorphic.
Isotonic Having equal osmotic pressures. See hypotonic, hypertonic.
Isthmus The segment of musculature between the medium bulb and basal bulb of the esophagus. See corpus, basal bulb.
See Figure 1

Iteroparity A species is considered iteroparous if it is characterized by multiple reproductive cycles over the course of its lifetime. See Semelparity.


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J2 an abbreviation for second-stage juvenile; the infective stage of many plant-parasitic nematodes.

J3 an abbreviation for third-stage juvenile

J4 an abbreviation for fourth-stage juvenile

Jaws A cuticular framework around the mouth which functions in grasping and holding; fundamentally 3 partite. Teeth in the broad sense.
Juvenile A nematode in a developmental stage which does not yet have functional gonads. Any immature nematode.
Juvenile Female A fourth-stage female in which the vagina and uterus are functional but the ovaries have yet to mature. See koriogamy.
Juxtaposition Situated adjacent to another. The act of being placed side by side. Apposition. See fornent.


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Kairomone A semiochemical, emitted by an organism, which mediates an interactions between species that benefits individuals of a species receiving the signal and harms individuals emitting the signal. See semiochemical, allomone, synomone, pheromone.

Karyokinesis Mitosis.
Karyoplasm The protoplasm of the nucleus. Nucleoplasm.
Keel-like See carina.
Keratin A segregate form of the cuticle corresponding to the external cortical layer. See cuticular layering.
Kidney-shaped See reniform.
Kinesis Movement induced by a stimulus and is not necessarily orienting. See taxis.
Knobs See stylet knobs.
Koriogamy The impregnation of a female nematode which possesses a fully developed vagina and uterus but an immature ovary.


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Labial Annule The labial disc.

Labial Basket A wide basket-like strucrure in the cheilostom that may be supported by six sclerotized curved plates, e.g. in the dorylaim genus Carcharolaimus.  See cheilostom..
Labial Crown of Papillae The anterior most circlet of papillae located on the lips. In forms with six lips two are lateral, two subdorsal and two subventral in position. In forms with other lip conditions they are accorded their respective positions. See anterior cephalic crown.
Labial Disc (or Labial Disk) The more or less circular font of cuticle about the oral opening and delimited posteriorly by the first transverse striation.
Labial Papillae Papillae located on the lips. See labial crown of papillae.
Labial Pulp Cavity See lip pulp.
Labial Sclerolization See framework.
Labial Muscles Specialized lip muscles apparently of the same origin as somatic muscles.

Labial Probola One of three cuticular processes (extensions) surrounding the mouth in cephalobids, one dorsal and two subventral; May be supported on a stem-like  peduncle.
Labial Setae The setae of the inner circlet and located on the lips or close to the mouth.
Labium (pl. Labia) Lip.

Lacuna A space; generally applied to a space between the cuticle and the epidermis and underlying muscle created as a consequence of the cuticle being less contractile and the muscle more contractile See cervical lacuna(e).
Lageniform Bottle-shaped. A more or less cylindrical body with a narrow elongate neck.  
Laggard An individual which matures very slowly or remains under the mature size.
Lamella (pl. Lamellae) A thin sheet, plate or layer. Sheet-like process, part or organ.
Lamellate Composed of thin sheets, plates or layers.
Lamelliform Having the form or composed of thin sheets, plates or layers.
Lanceolate Oblong and tapering to a point.

Lance-shaped. Spear-shaped. See oblanceolate.
Lancets Shall sharp teeth in the buccal cavity of some nematodes.
Lancet-shaped Formed like a lance commonly sharply pointed and two edged. See lanceolate.
Lancinate To pierce a cell or organ, etc. with a tooth or stylet.
Larva (pl. Larvae) In the nematological sense, the immature form of a nematode. See nymph, juvenile, neotony.
Larval Stages The periods of growth between molts. See Instar.
Larvated Eggs Embryonated eggs.
Larviparous Reproducing by bringing forth living larvae. Ovoviviparous. See viviparous, oviparious, fissiparous, reproduction.
Laterad Toward the side and directed away from the median line.
Lateral Relating to, belonging to, attached to, or situated at the side. The position on the nematode body situated 90 degrees from the median line and perpendicular to the anteroposterior axis. See position. See
Figure 22, Figure 23..

Lateral Alae Lateral or sublateral extensions of the cuticle which extend along the body in both males and females.  See caudal alae, bursa.
Lateral Cephalic Inflations Cuticular inflations confined to a limited lateral region just posterior to the lips. See inflation of the cuticle..
Lateral Cords Longitudinal hypodermal thickenings lying in the lateral position. See cords, dorsal cord, subdorsal cord, ventral cord, subventral cord. See Figure 3, Figure 21.
Lateral Fields A form of cuticular configuration above the lateral cords.

Lateral gene transfer  See horizontal gene transfer
Lateral Glands Lateral hypodermal glands.
Lateral Grooves Involutions.
Lateral Guiding Pieces Cuticularized structures which guide the spicule.
See Figure 5, Figure 20.
Lateral Hypodermal Glands Two sublateral rows of unicellular glands lying in the lateral cords and communicating to the exterior by short ducts through pores in the cuticle. See hypodermal glands.
Lateral Lines Involutions.
Lateral Membrane A cuticular flap situated on both sides of the vulval slit in some nematodes. See epiptygma, vulvar flap.
Lateral Nerves Nerves originating mostly at the lateral ganglia. Of a sensory nature with ganglionic swellings along the lateral cords, supplying a sensory branch to the cervical papillae when present and enter the lumbar ganglia posteriorly.
Lateral Organs The amphids. See organs of the lateral cords.
Lateral Papillae The amphids.
Lateral Pore An opening to the lateral hypodermal glands. See Figure 3.
Lateral Ridges A broad longitudinal ridge which covers the lateral cord and in some forms may be subdivided superficially by involutions. See longitudinal ridges.

Lateral Wings Longitudinal lateral elevations of cuticle which extend along all or part of the body, especially from the base of the esophagus to the anal region. See lateral field.
Lateroanal In the lateral position at the level of the anus. See position.
Laterodorsal The position on the nematode body situated 45 degrees from the dorsomedian line and perpendicular to the anteroposterior axis. Submedian. See position, lateroventral. See
Figure 22, Figure 23..
Retractor Spiculi A muscle extending anteriorly from the manubrium, to the body wall between the laterodorsal somatic muscle field and the lateral cord.
Laterosubdorsal The position on the nematode body situated 60 degrees from the dorsomedian line or 30 degrees dorsad from the lateral line and perpendicular to the anteroposterior axis. See position.
Lateroventral The position on the nematode body situated 45 degrees from the ventromedian line and perpendicular to the anteroposterior axes. Submedian. See position, laterodorsal. See
Figure 22, Figure 23..
Retractor Spiculi A muscle extending anteriorly from the manubrium to the body wall between the lateroventral muscle field and the lateral cord.
Latitude A site in a nematode measured on the meridian of a cross section.
L.A.Value The logarithm of the concentration in arbitrary units of the active root diffusate factor and is proportional to its activity. See log activity values.
Layered See lamelliform.

LC50 The concentration of a chemical at which 50% of the target organisms are killed; for example, 10 mg of chemical per liter of air or water. See lethal concentration.

LD50 The dosage of a chemical, based on the mass of the affected organism, at which 50% of the target organisms are killed; for example, 10 mg of chemical per Kg of target organism tissue. See lethal dosage.
Leachate The dissolved soluble constituents of a root diffusate and its solvent. See root diffusate.
Leaching The result of percolating a solvent through a substrate to dissolve its soluble constituent.
Leaf Blotch Disease A pathological condition of Chrysanthemum incited by Aphelenchoides ritzemabosi.
Leaf Crown The corona radiata.
Leaf Drop A disease condition of fig trees incited by Paratylenchus hamatus and Xiphinema index.
Leaf Galls Leaf swelling which serve as structures for the maturation and reproduction of the nematode parasites and are comparable to seed galls.
Leather-like See coriaceous.

Lectins Sugar-binding proteins which are highly specific for the sugar component to which they bind. Often involved in biological recognition between cells and proteins.

Lectin Binding The use of sugar-binding proteins to adhere to specific regions of cell walls. For example, some bacteria use lectins to attach themselves to the cells of the host organism during infection.

Lectotype The specimen selected as holotypc from the syntypes upon which a species revision is based. See type.
Legs Hollow, glandular ambulatory setae.
Lcmniscate Ribbon-like, having the shape of an "8". See panduriform, eight-shaped structure.
Lemon-shaped See citron-shaped. Prolate.
Lenticular Lens-shaped. Having the form of a biconvex lens.
Leptoderan Caudal alae which do not meet posterior to the tail. See peloderan.
Lesion An injury, wound or morbid structural change. A localized spot of diseased tissue.

Lethal Concentration The concentration of a chemical at which the target organisms are killed; for example, 10 mg of chemical per liter of air or water. See LC50.

Lethal Dosage The dosage of a chemical, based on the mass of the affected organism, at which the target organisms are killed; for example, 10 mg of chemical per Kg of target organism tissue.  May be expressed based on ingestion (Oral Lethal Dosage) or skin contact (Dermal Lethal Dosage). See LD50.

Lethargy A state of inaction.
Life Cycle The successive series of changes through which an organism passes in the course of its development. See generation.
Life History The record of events in the development of an individual.
Liganientum Cephalo-esophageal arcade cells.
Lighter Striae Intermediate striae.
Ligneous Wood-like. Woody.

Limnic Living in aquatic environments with low salt content. Freshwater environments.
Linear Resembling a line. Having a form long and uniform in width.
Lineate Having lines or stripes. Having a form long and uniform in width.
Linguiform Tongue-shaped.
Lingulate Tongue-shaped.
Ligulate Strap-shaped.
Lip Cap The anterior most cuticular annulation, disc-like in shape, circumoral and usually thicker than adjacent head annules.
Liplets Diminutive lip-like structures frequently projecting.
Lipoid Membrane A thin, delicate covering membrane immediately beneath the egg shell of fertilized eggs. The inner membrane. See the fertilization membrane.
Lip Pulp The interior tissue of the lips composed of several large, elongate cells. See clavate cells, fiber cells, arcade cells, filling cells.
Lip Region The cuticular area from the basal ring forward. Figure 40.
Lip Sclerotizations The cephalic framework.
Lip Sector The several regions of the anterior cephalic region as delimited by the radial blades.
Littoral Fauna Organisms dwelling between high and low tide lines, usually close to the shore. See benthic fauna, pelagic fauna.
Lively See alacrious.

LM Light microscope or light microscopy
Loam The textural class name for soil having a moderate amount of sand, silt and clay. Loam soils contain 7 to 27 percent of clay, 28 to 50 percent of silt and less than 52 percent of sand.
Lobe A generally rounded part or projection of a part or organ separated from neighboring parts by fissures or constrictions.
Lobiform Shaped like a lobe or rounded process.
Lobulate Consisting of or with many small lobes or lobules.

Locus The specific position on a chromosome where a gene or genetic sequence is located.
Log Adivity Values A L. A. of zero is that concentration of hatching factor of root diffusate which just fails to give a hatch significantly higher than water. A L. A. of I represents a value of 10 times, a L. A. of 2 represents a value of 100 times, etc. The logarithm of the concentration of the active factor of the root leachate.
Longitudinal Extended in length. Lengthwise.
Longitudinal Alae Longitudinal thickenings of the cuticle, generally lateral or sublateral, extending the length of the body. See alae.
Longitudinal Axis The long axis from head to tail. Anteroposterior axis.
Longitudinal Cords The longitudinal thickenings of the hypodermis. See cords.
Longitudinal Fibrils Noncontractile or static fibers of the muscle sarcoplasm. See transverse fibrils.
Longitudinal Fields The longitudinal ridges.

Longitudinal Lines The longitudinal ridges of some authors and the longitudinal cords of others.
Longitudinal Lip Groove A cephalic cuticular depression above each of the radial blades of the cephalic framework.
Longitudinal Lip Striae Generally faint, irregularly spaced markings of the cephalic cuticle which terminate at the cephalic constriction, See  constriction.
Longitudinal Markings This form of cuticular ornamentation may he ridges, alae or the result of interruptions in the transverse markings.
Longitudinal Plane The lengthwise plane or dimension ala body. See sagittal plane, transverse plane.
Longitudinal Ribbon The lateral field.
Longitudinal Ribs The longitudinal ridges of the cuticle.
Longitudinal Ridges Local longitudinal thickenings of the two external cuticular layers which extend the whole body length. See lateral ridges.
Longitudinal Striation In the cuticle a groove parallel to the longitudinal axis. See transverse striation.
Longitudinal Thickenings The lateral fields. The lateral cords.

Lotic Inhabiting rapidly moving freshwater.
Lumbar Ganglia Large ganglia in the anal region receiving the lateral nerves and ventrolateral connectives.
Lumen The cavity delimited by the walls of a tubular vessel.
See Figure 1, Figure 3.
Lumen Rays The esophageal radii.
Lysigenoma (pl. Lysigenomata) A structure formed most commonly in root tissue by the coalescing of several cells through dissolution of common walls under stimulation of salivary secretions by gall-forming nematodes and some other kinds. Giant cell. See hypertrophy, hyperplasia, nurse cell.
Lysis Cell destruction. A tissue dissolution process.


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Macerate To waste away. To soften, separate and wear away. See comminute, triturate.

Macrobenthic Invertebrates living within or on the surface of aquatic sediments and that are larger than 1 mm in size.
Macrophagous Feeding on objects of a relatively large size. See feeding, microphagous.
Macroscopic Visible to the unaided eye. See microscopic.
Macula A spot, especially one not elevated above the surrounding level. See ocellus.
Male Intersex An individual which begins development as a male but, completes development as a female See intersex, female intersex.
Male Plant A disease of strawberry incited by Aphelenchoides fragariae. See dwarf.
An abnormal development or formation of a part or structure.

Mammalian Toxicity The effect of a pesticide on non-target human and warm-blooded animals.  See Toxicity.

Mammiform Nipple-shaped. Breast-shaped.
Mammillate Having nipple-like protuberances or processes. Digitate.

de Man Formula See De Man Formula.

de Man Indices The De Man formula.
Mandibles Hard, strong cuticularized structures about the mouth which function in biting or  grasping.
Manubrium The enlarged, cephalated proximal portion of the spicule. See Figure 16, Figure 20.
Marginal Fibers Fibers, probably of an elastic nature, which extend from the ends of the lumen of the esophageal radii to the bounding membrane of the esophagus.
Marginal Tubes The terminal cylindrical endings of some esophageal radii; the radii of other forms may have convergent terminals. See Figure 13.
Marine Living in the sea. See aquatic, arenicolous, edaphic, hypogaeic, limnic, rheophile, terrestrial, terricolous, xerophilous, cavenicolous, fossorial.

Marsupials Mammals with short gestation period that carry young in a pouch; endemic to Australia
Mass Invasion A situation where large numbers of nematode parasites attack a host simultaneously.
Mass Hatching The phenomenon of large number of nematode eggs hatching within a short period of time in response to some stimulus.
Massive Gland A simple roundish pear-shaped cell or an elongate tubular cell of uniform diameter and devoid of internal cavities. Salivary gland.
Masticatory Apparatus Organs or structures adapted to the chewing of food.
Matricin A fibroid segregate of the cuticle corresponding to the matrix layer. See cuticular layering.
Matrix The enveloping substance within which something originates or develops.
Matrix Glands In Meloidogyne spp. six glands, two subdorsal, two lateral and two subventral which secrete the gelatinous matrix through the anus and in which the eggs eventually are imbedded.
Matrix Layer The cuticular stratum consisting of a spongy mass between the fibrillar layer and the boundary layer. See cuticular layering.
Maturation The entire process by which diploid primordial germ cells are transformed into haploid gametes.
Maturation Division Mitosis.
Mediad Toward the median plane or line.
Medial Pertaining to, directed toward, situated at, or occurring in the middle.
Median A midway point in position. Situated in the middle position. A plane of division dividing a bilateral organism into right and left halves. See position.
Median Bulb The metacorpus. Figure 40
Median Esophageal Bulb The metacorpus.
Median Pseudobulb The metacorpus.
Medioventral Ventromedian. See position.
Medium (pl. Media) Substratum.

Meiobenthos The assemblege of microinvertebrates, including nematodes and copepods, that inhabit freshwater and marine aquatic systems.

Meiofauna  Organisms that pass through a 1-mm mesh sieve and are retained on a 42- or 63-um mesh sieve
Meiosis The process by which a nucleus halves its chromosome number from the original diploid state to the reduced haploid state. Typically meiosis consists of two nuclear divisions: in one, without prior longitudinal splitting the chromosomes separate resulting in half of the original diploid number being in each resulting daughter nucleus; in the other the process is essentially mitotic in character. Four haploid cells are thus produced by the two divisions.

Meiotic Parthenogenesis Reproduction without fertilization and with a meiotic reduction division of the unfertilized egg cell.  Diploid number is re-established by fusion with the nucleus of a polar body.  See Parthenogenesis, Automictic Parthenogenesis.

Mensural  Of or pertaining to measure. Measurable.
Menstruum A solvent. Any substance capable of dissolving a solid body.
Mentek A disease of rice incited by Hirschmanniella oryzae.
Meridic Pertaining to a medium in which the chemical identity of certain, but not all, of the absolutely essential molecules has been established. Media in which most of such requirements are known are highly meridic; those in which but one or a few are known are slightly meridic. See holidic, oligidic.
Mermithaners Male ants infected with a species of mermithids. See mermithogynes, mermithostratiotes, mermithergates.
Mermithergates Worker ants infected with a species of mermithids. See mermithogynes, mermithergates, mermithostratiotes, mermithaners.
Mermithogynes Female ants infected with a species of mermithids. See mermithergates, mermithostratiotes, mermithaners.
Mermithostratiotes Soldier ants infected with a species of mermithids. See mermithogynes, mermithergates, mermithaners.
Mermithoid Esophagus Having a degenerate musculature and possessing a long cuticularized tube with the cells of the esophagus and glands distributed in an irregular manner.
Merogony A mode of reproduction where the spermatozoon enters the egg cell and provides stimulus to further embryonic development but does not fuse with the nucleus to form a zygote.
Meromyarian Having eight rows of longitudinal muscle cell between hypodermal cords. See platymyarian, holomyarian, polymyarian.
Mesenteries A delicate membrane which invests the intestine and the gonads and extends from the esophageal membrane to pseudocoelomic membranes covering the musculature. See pseudocoelomic membranes, isolation tissue.
Mesenteron The intestine.
Mesorhabdions The walls of the mesostom.
See Figure 1, Figure 10.

Mestostegostom The second anteriormost region of the stegostom, the mesostom. See mesostom.
Mesostom A subdivision of the protostom as distinguished by clefts in the rhabdions and is preceded anteriorly by the prostom and posteriorly by the metastom. See prostom. metastom. See Figure 10.

Messenger Ribonucleic Acid  See mRNA.

Metabarcoding See DNA Metabarcoding.

Metabolic Footprint A measure of the contribution of an individual, species or guild of organisms to ecosystem function or service based of their utilization of carbon and energy. See metabolism, abundance, ecosystem services.
Metabolism The chemical changes occurring in living organisms by which energy is provided for vital processes and activities and new material is assimilated to repair the waste. The sum of the processes of anabolism and catabolism which take place in living matter.

Metabolites The substrates, intermediates and products of cell metabolism.

Metabolomics Study of chemical processes invol;ving metabolites. See metabolites.
Metacentric Having two equidistant arms due to the median position of the centrome. See telocentric.
Metacorpus The posterior subdivision of the corpus taking an ovate form and being preceded by a cylindrical anterior segment. The median bulb. See procorpus.
See Figure 1.
Metagenesis Reproduction where the immediate descendants are dissimilar from the parents with the alternate type produced only with every other generation or after a period of several generations. The alternation of sexual and asexual reproduction in the life cycle of certain organisms. Alternation of generations.

Metagenomics The study of genetic matterial recovered from an environment or from an assemblage of organisms. See genomics.
Metameric Segmentation The repetition of elements of the main organ systems of the body along the length of the body.  For example, in the earthworms (Annelida), each of the externally visible rings marks a segment (or metamere) of the body that contains a similar pattern of blood vessels, nerves, excretory organs, external features, etc.; similar patterns are evident in Arthropoda.  In the Vertebrata, segmentation is most obvious during embryonic development; in adults it is confined to mesoderm derivatives such as muscle and skeleton, e.g., repetition of vertebrae and ribs.

Metamorphosis A pronounced reorganization of body tissues and form in changing from one stage of development to another, as from a larva to an adult. See complete metamorphosis, incomplete metamorphosis.

Metaneme Filamentous organs located in or near lateral hypodermal chords.  Interpreted as stretch receptors, known in some nematode species, but not C. elegans. Occur in nematodes of the order Enoplida.  Have a central scapulus and anterior and posterior filaments

Metaphase A stage in mitosis or meiosis when chromatids are arranged on the equatorial plane of the spindle. See prophase, anaphase, telophase.
Metarhabdions The walls of the metastom.
See Figure 1, Figure 10.

Metastegostum the second  last region of the stegastom, the metastom, See metastom.
Metastom The posterior subdivision of the protostom as distinguished by clefts in the rhabdions. See  mesostom, prostom. See  Figure 10, Figure 40
Metatype In the broad sense, a specimen compared by the author of a species with the type and determined to be conspecific. In the narrow sense, a topotypic specimen compared by the author of a species with the type and determined by him to be conspecific. See type.
Myceile, Micella, Micell In colloids a unit of structure derived from complex molecules.
Microbenthic Invertebrates living within or on the surface of aquatic sediments and that are less than 63 um in size.

Microclimate The local climatic condition of a particular niche resulting from the modification of the general climate condition by local differences in relief, exposure and cover.
Microfilariae Young or embryonic filarioids of the Filarioidea.
Micron (µm, pl. Micra) A unit of measurement equal to 1/1,000 of a millimeter, designated by the Greek letter mu.
Microphagous Feeding, on objects of a minute size. See feeding, bacteriophagous, macrophagous.
Microplot A small duplicate of a field plot designed to be as similar as possible.

Microphytobenthos The community of unicellular eukaryotic algae, especially diatoms, and cyanobacteria that at the surface of illuminated  marine and freshwater sediments; the primary producers at the base of benthic foodwebs.

Micropyle The minute opening in the investing membrane of an egg permitting the entry of a spermatozoon.
Microscopic Small in size. Not visible to the unaided eye. See macroscopic.
Midbody The equatorial region of the nematode body. Median. See equatorial.
Middle Cuticular Layer This layer corresponds to the matrix layer of the cuticle, See cuticular layering. See Figure 21.
Middorsal The true dorsal line. Dorsomedian, See position.
Middorsal Nerve The dorsal nerve.
Midgut The intestine proper, from the posterior of the esophagus to the anterior of the rectum See foregut, hindgut.
Midintestine The intestine proper.
Midventral The true ventral line. Ventromedian, See position.
Midventral Glands Supplements.
Migrate To move from one feeding site or location of development to another.
Migratory Nematodes Endoparasitic and ectoparasitic nematodes which are capable of feeding and moving about in roots or soil.
Mitosis The process by which a nucleus divides into two nuclei. Typically mitosis consists of four successive stages; (1) the prophase, in which the chromatin forms long thread-like structures termed a spireme (or several spiremes) which shorten, thicken and split longitudinally becoming rearranged into paired chromosomes; (2) the metaphase, the nuclear membrane dissolves, a spindle is formed and the chromosomes come to lie at its equatorial plane; (3) the anaphase, the chromatids separate and move to opposite poles of the spindle; (4) the telophase, the chromosomes uncoil, become elongated and eventually become indistinguishable. A nuclear membrane is formed and the spindle disappears. Each daughter nucleus contains the original (diploid) number of chromosomes. If the cell is to divide the cytoplasm cleaves at this stage. The period of time involved in mitosis varies greatly but is usually between one-half and three hours.
Mitotic Parthenogenesis Reproduction without fertilization and by mitotic division of egg cells. See Parthenogenesis, Apomictic Parthenogenesis.

Modified Changed somewhat in form or other characteristics.
Molt, Moult To cast off the cuticle. See ecdysis, instar.
Moniliform Constricted at intervals so as to resemble a string of beads. Beaded.
Moniliform Glands In the demanian system posterior glands which accompany the ducts which open to the exterior shortly anterior to the anus.
Monodelpbic Having one ovary. See amphidelphic didelphic, prodelphic, opisthodelphic, polydelphic. See Figure 25,
Figure 26.
Monogenesis Development from a single hermaphroditic parent. Asexual reproduction. See reproduction.
Monogenetic Development where the larvae resemble the parents. See heterogenetic, reproduction.
Monogony The development of eggs without benefit of fertilization by spermatozoa. See parthenogenesis, reproduction.
Monograph A treatise in detail on a particular subject.
Monomorphic Exhibiting only one form, especially applied to species which contain only one sex (female). See dimorphic, heteromorphic, polymorphic,.
Monophagous Feeding on only one kind of food, especially nematodes feeding on plants. See feeding.
Monophyletic Derived, developed or of a single stock or common ancestral form and including all the descendants of the common ancestor. See polyphyletic, paraphyletic, polyparaphyletic.

Monophyly A group of organisms exhibiting the monophyletic condition. See monophyletic, paraphyly.
Monoploid Having the gametic number of chromosomes. Haploid. See aneuploid, euploid, heteroploid. hyperploid, polyploid.
Monorchic Having one testis. See diorchic, reproduction.
Monotremes Egg-laying mammals of the order Monotremata; the only egg-laying mammals.
Monotype A holotype of a species based on a single specimen. See type.

Monovarial. See Monodelphic.
Monoxenic Pertaining to the rearing of an organism with only one known species of associated organism. See gnotobiotic agnotobiotic, xenic, axenic, synxenic, dixenic. trixenic, polyxenic.
Monoxenic Culture A nematode population containing only one other species of organism. See pure culture, aseptic culture, agnotobiotic culture, axenic culture.

Monoxenous Having a single host species in the life cycle. See Monoxenic.
Moon-shaped See bicorn, crescentiform, seleniform, semilunar.
Mordant In staining, any substance which when added to the dyestuff combines to form an insoluble compound to produce a fixed color in the material stained.
Moribund In a dying condition. Near death.
Morphogenesis Development or evolution of morphological characters.
Morphology The study of form and structure of organisms.
Morphometry Measurement of external form. See De Man Formulae.

Morphometric Parameters Measurement of external form. See De Man Formulae.

Morphotype The type of the dimorphic form of a species. See type.
Morula The globular mass of cells formed by holoblastic cleavage of the egg in its early development.
Morular Organ A region at the ovarial end of the uterus where the egg shell is formed.
Mosaic-like See tessellate.
Moult Var. of molt.
Mouth The oral aperture.
See Figure 1.
Mouth Capsule The buccal cavity.
Mouth Spear See stomatostyle, ondontostyle. onchiostyle.

MPB See Microphytobenthos
mRNA Messenger Ribonucleic Acid.  The molecule of ribonucleic acid (See RNA) that is transcribed from a DNA (See DNA) template and carries the coding information for the structure of a protein to the ribosomes (See Ribosome), the sites of protein synthesis.

Mucivorous Feeding on the protoplasm of plants. See feeding.
Muck Soil Highly decomposed organic soil material developed from peat. In gencral, muck has a higher mineral or ash content than peat and is decomposed to the extent that the original plant parts cannot be identified.
Mucoid A segregate of the cuticle (glucoprotein).

Mucro An abrupt point, tip or process which terminates the nematode tail; a cuticular projection.
Mucron A small knob-like ending on a terminus.
Mucronate Ending abruptly in a point, having a mucro.
Mucus The gelatinous matrix.
Multispire Two or more turns of a spriral. See spiral.
Mural Stylet A stylet derived from the wall of the stoma.
Mural Tooth A cutting or piercing structure situated on the pharyngeal wall but formed further back in the esophagus.
Muscle Fibers See fibroplasm.
Muscle Fields The somatic muscles divided into groups by the cords and named according to position. See dorsosubmedian muscle fields, ventrosubmedian muscle fields. See Figure 21.
Muscles of Special Function Muscles of the same origin as somatic muscles but limited as to region and function. See somato-esophageal muscles, somato-intestinal muscles, intestinal muscles, anal muscles, vulvar musculature, bursal musculature, spicular muscles.
Musculature The muscles of a body with special reference to their arrangement and function.
Musculus Bursae Basalis A bursal muscle arising from the ventral side of the bursa extending dorsally to the root of the dorsal ray. See bursal musculature.
Musculus Costae Dorsalis A much branched bursal muscle arising mediodorsally in the dorsal ray, extending anteriorly to become trifurcate then the median arm splits into four parts. See bursal musculature.
Musculus Costae Lateralis Externus Anterior Bursal muscles arising anterior to the musculus costae lateralis externus posterior, extending posteriorly to the base of the ventral rays. The muscles probably function to extend the bursa. See bursal musculature.
Musculus Costae Lateralis Externus Posterior A bursal muscle arising anteriorly dorsad of the lateral cords, extending posteriorly and becoming trifurcate at the base of the lateral rays. The muscle probably functions to extend the bursa. See bursal musculature.
Musculus Cestrum Literalism Internist A bursal muscle arising as paired sub median muscles at the body wall anterior to the intestino-rectal valve; each laterally extended branch enters the root of the lateral ray. The muscle probably functions to bend the bursa inwards. See bursal musculature.
Mushroom-shaped Stalked with an umbrella top.
Mutant An organism that undergoes mutation.
Mutation A genetic variation with the progeny differing from their parents in one or more characters.
Mycophagous Feeding on fungi. See feeding.


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Nanism Dwarfishness. Being small in stature.
Natatory Parts Structures adapted or used for swimming.
Natural Enemies Organisms detrimental to the survival of others.
Natural Selection The process of population or specific stress by the environment tending to eliminate those forms least adjusted to survive under the conditions in which they live.
Neallotvpe An allotype described after previous publication of the original description. See type.
Near-Cauliflower Intermediate forms of disease expression between the healthy plant and cauliflower dwarf.
Nearctic Pertaining to or belonging to the nearctic region.
Nearctic Region That part of the Holarctic Realm considerd the New World, which covers most of the North American continent and Greenland. See Palearctic Region, Holarctic Realm.
Neck That portion of the nematode body from the base of the lips to the base of the esophagus. See cervical.
Necrobiosis The death of an individual cell. See necrosis, nematosis.
Necrobiotic Food Tendencies The preference of plant cells for food at an early stage of necrosis by pathogenic nematodes.

Necromenic. Using the feeding strategy that is described by Necromeny. See Necromeny
Necromeny Feeding on microbes that exploit the cadavers of dead organisms.but not being actively involved in killing the organism

Necrophagy Cannibalism of dead organisms by others of the same species, an effective route of infection of parasitic organisms among hosts..

Necropsy A post-mortem examination. See autopsy.
Necrosis The death of cells surrounded by living tissue, specifically death to cells in mass in contrast to necrobiosis. See necrobiosis, nematosis.

Necrotic In a dead and decaying condition. Affected with or characterized by necrosis.
Nectaries Plant cells near the heads of sedentary nematodes which have been stimulated to enlarge by saliva excretions and from which the nematodes derive their sustenance. Nurse cells, giant cells.
Needle-shaped See acerate, acerose, acicular, aciform, spiculiform, spicule.

Negentropy Negative entropy or reverse entropy; the opposite of randomness or chaos; a greater degree of organization and structure, resulting in increase in functions and services of the system. See Entropy.
Nekton Fauna Animals that swim freely by their own efforts. See palagic, plankton, benthos.
Nema A term for any individual of the phylum Nematoda.
Nemacide See nematicide.

Nemata An alternative name for the phylum Nematoda.
Nematicide Any agent lethal to nematodes.
Nematization The state of being populated, infested or infected with nematodes.
Nematize To populate, infest or infect with nematodes.
Nematocide Var. of nematicide.
Nematoda The name of the phylum constituted by nematodes.
Nematode A term for any individual of the phylum Nematoda. See eelworm, nema, roundworm, threadworm.
Nematode Index The numbers of nematodes per unit of substratum:

      0 = none  = 0
      1 = rare =  1
      2 = infrequent = 10
      3 = frequent  =  100
      4 = abundant  =  1,000
      5 = very abundant = 10,000
See root-knot index.
Nematode wool A mass of resistant, desiccated Ditylenchus larvae frequently found on bulb crops and others. Wool.
Nematodologist Var. of nematologist.
Nematological Pertaining to, or having the character of, nematology.
Nematologist One versed in nematology.
Nematology The body of science centered on nematodes.
Nematophagous Feeding on, or deriving sustenance from, nematode bodies. See feeding.
Nematosis A morbid condition due to parasitism by nematodes. See necrobiosis.

Nematostat A chemical, situation or phenomenon which holds a nematode population in equilibrium.
Pertaining to a nematotoxin.
Nematotoxin Any substance lethal to nematodes.
Nemic Belonging to, or pertaining to, nematodes.
Nemic Index See nematode index.
Nemicide See nematicide.
Nemin The substance or substances that cause trap formation by predaceous fungi. See Endogenous nemin.

Neodont A tooth emerging at the anterior part of the esophagus in some nemaode taxa, e.g. genus Boehmiella.

Neontology The study of recent organisms as distinguished from paleontology.
Neoteny Larval characteristics persisting in the adult. See reproduction.
Neotony Sexual maturity in the larval stage. See paedogenesis, reproduction.

Neotropical Realm The biogeographical region encompassing tropical regions of Central and South America.  See Afrotropical Realm, Holarctic Realm, Australasian Realm.
Neotype A specimen from the original type locality designated as a new holotype. Plesiotype. See type.
Nepo Virus A plant virus with polyhedral particles transmitted by nematodes in the Longidoridae.  See Tobra Virus.

Neritic Fauna Organisms dwelling below the low tide line to depths of about 600 feet and subject to some wave action. See benthonic fauna, pelagic fauna.
Nerve Ring A belt, broad and flat in slender nematodes but narrow in forms with a large esophagus, containing cell bodies of neurons
distributed around it. The nerve cells are generally too diffuse to be termed true ganglia. The nerve ring represents the dorsal and ventral connections between the lateral ganglia. See circumenteric ring, circum-esophageal commissure
. See Figure 1.
Nests Clusters of nematodes within plant tissue.
Nests Centers of nuclear division of a syncytial hypodermal cell.
Net-like See reticulate.

Neural Larva Migrans A zoonotic infection in which humans are an accidental (not definitive) host for a nematode parasite of animals.The nematodes cannot mature in humans and cause damage by migrating into the central nervous system and brain; often caused by Baylisascaris infection..  See Cutaneous Larva Migrans, Visceral Larva Migrans.
Neuron (pl. Neurons) A nerve cell and its series of processes.
Niche A habitat or environment best suited for the survival of the organism.
Nipple-like See mammillate, digitate.
Noncoelomate Lacking a true body cavity. See pseudocoelom.

Non-host Usually used when no varieties of a plant species support reproduction of a nematode species.  For example, Citrus spp. are non-hosts to Globodera rostochiensis.  See host.
Northern See
Noxious Injurious. Destructive. Baneful.
Nuclear Nests See nests.

Nucleobase The fundamental units of the genetic code; the bases adenine (A), cytosine (C), guanine (G) and Thymine (T) are the constituents of DNA while A, G, C and Uracil (U) are the components of RNA. See DNA, RNA, nucleotide.
Nucleoplasm The protoplasm of the nucleus as distinguished from cytoplasm.

Nucleotide A molecular component of DNA or RNA comprised of three subunit molecules, a nucleobase, a 5-carbon sugar (ribose or deoxyribose) and a group of one to three phosphate molecules. See nucleobase, DNA, RNA.
Nucleus (pl. Nuclei) A well defined and specialized portion of cellular protoplasm held as being of crucial importance to cell physiology and heredity. It
usually consists of nucleoplasm bounded by a
nuclear membrane and composed of 1mm, chromatin and differentiated structures such as nucleoli. See Figure 7, Figure 8, Figure 21.
Nurse Cells Modified plant cells about the heads of sessile
nematodes which feed on the cells. See giant cells, nectaries
Nursery A center of nematode infestation in plant tissue well isolated from many population inhibiting pressures.
Nymph An immature individual having the form
characteristic of the adult. In Entomology "larva" is the term for individuals which undergo complete metamorphosis and to be distinguished from "larva" in the nematological
sense which undergo incomplete metamorphosis. See juvenile.

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Oar-shaped See remiform, spatulate.

Oblanceolate Inversely lanceolate.
Oblate Flattened, as a
spheriod depressed at two opposite poles. See prolate.
Obligate Parasite An organism only capable of deriving its food from living organisms. See facultative parasite, facultative saprophyte,
obligate saprophyte.
Obligate Saprophyte Organisms which subsist on dead organic matter or from available inorganic material and have no relationship with living cells. See obligate parasite, facultative parasite,
facultative saprophyte.
Obligatory Aerobic Requiring the presence of atmospheric oxygen in order to live. See anaerobic, facultative aerobic, facultative anaerobic, obligatory anaerobic.
Obligatory Anaerobic Growing only in the
absence of atmospheric oxygen. See aerobic, anaerobic facultative aerobic, facultative anaerobic, obligatory aerobic.
Oblique Slanting. Inclined.
Cuticular Markings Conspicuous oblique beneath the cortical layer of the cuticle.
Oblong Elongated.
Obovate Inversely ovate. See ovoid.
Obtuse Not pointed. Blunt. See pointed.
Ocellus (pl. Ocelli) An eye spot. A pigmented spot; possibly associated with detection of light. See macula.
Ochlesis Any detrimental condition due to overcrowding.

Ocular Larva Migrans (OLM) A zoonotic infection of the human eye caused invasion of the eye by larvae of Toxocara canis (dog roundworm). See visceral larva migrans, neural larva migrans.
Ocular Micrometer Disc A ruled glass plate used in the eyepiece of a microscope for measuring minute objects.

Ocular Toxocariasis See Ocular larva migrans
Odontium (pl. Odontia) A labial tooth (teeth) situated on the pharyngeal wall but formed in the esophagus and moved forward. See onchium.
Odontostyle A stylet terminating with a dorsally oblique aperture. The stylet was derived through evolutionary development from an odontium and originates in the esophagus wall. See onchiostyle. See Figure 4. See spear.
Oecology Var. of ecology.
Oesophagus Var. of esophagus or pharynx.

Offset Not in line with the body contour or not contioguous with the axis of an organ, for example, an offset head or an offset spermatheca.
Oligidic Pertaining to a medium, consisting wholly or largely of crude materials in which no molecule (other than water) has been established as an absolute nutritional requirement. See holidic, meridic.

Oligonucleotide Short DNA or RNA molecules that function in the regulation of gene expression. See Primer.
Oligophagous Feeding on a few kinds of food, especially nematodes with a limited host range. See feeding.
Oligozoic A habitat having few kinds or numbers of animals.

OLM See ocular larva migrans.

Omasum. The third stomach of a ruminat which receives food from the reticulum and passes it to the abomasum. See abomasum.

Omics Informal description of branches of science with names ending in -omics and collectively characterizethe translation of pools of biological molecules into structure and function of organisms. See genomics, metagenomics.
Omnivorous Subsisting on all types of food, especially feeding on both animal and vegetable material. See feeding.

Omnivore-Predators A grouping of nematodes  with feeding habits that include feeding on other living organisms. See Generalist Predators, Specialist Predators.

Onchiophore The curved posterior extension of the onchiostyle feeding structure in Trichodoridae.

Onchiostyle A feeding structure with an onchium or tooth anteriorly and an extension or onchiophore posteriorly.
Onchium (pl. Onchia) A solid tooth (teeth) which was formed "in place" as compared to the development of an odontium in the esophagus then moved forward. See Figure 4.
Onchus An onchium.
Onion Bloat A disease of onions incited by
Ditylenchus dipsaci.
Ontogenetic Pertaining to the life history or development of the individual organisms. See phylogenetic.
Ontogeny The life history or development of an individual as distinguished from that of the species and higher groups. See phylogeny.
Oocyte A female gamete prior to maturation. See Figure 27.
Oogenesis The formation of the egg, its preparation for fertilization and development.
Oogonium (pl. Oogonia) The first stage in the differentiation of an egg cell from a primordial germ cell. See OOcyte.
Ooplasm The cytoplasm of an egg.
Oosperm A fertilized ovum. A zygote. Oosphere An unfertilized ovum. A female reproductive cell.
Opercular Plug A removable covering from the hiatus of some nematode egg shells allowing the escape of the larva.
Opisthodelphic Having a single ovary posterior to the vulva. See amphidelphic, monodephic, prodelphic, didelphic
. See Figure 26.
Opposed Pertaining to structures that are opposite each other, either located on each side of the body or directed anteriorly and posteriorly.

Orad Toward the oral aperture.
Oral Aperture The anterior entrance into the stoma.
See Figure 1, Figure 6, Figure 22, Figure 23..
Oral Capsule The stoma.
Oral Cavity The stoma.

Oral LD50  The dosage of a chemical, based on the mass of the affected organism, at which 50% of the target organisms are killed when the material is ingested; for example, 10 mg of chemical per Kg of target organism tissue. See Lethal Dosage.
Oral Opening The oral aperture.
Oral Orifice The oral aperture.
Order In the systematic arrangement of organisms into groups or categories denoting natural relationships a category ranking above a family and below a class. See classification.
Belonging to, or characteristic of an Order.
Ordinate The vertical line perpendicular to the transverse line (abscissa) to show by graphic design the relations of two series of facts. See abscissa.
Ordinate Arranged in rows, such as
cuticular ornamentations, etc..
Organe Cephalique
The head cleft.
Organic All carbon compounds derived from living organisms.

Organism An organic entity so constituted as to carry on the various functions of life. A living creature.
Organs of Sense See tactile organs,
amphids, phasmids, ocellus.
Organs of the Lateral Cords
A conspicuous series of gland-like structures giving the esophagus an appearance of alternate tissues.
Organ Z A muscular organ of unknown function, bearing three or four inner
apophyses, lying between the spermatheca and the uterus. See Figure 24.
Orifice An aperture.
Opening of a tube, duct, etc. Ornamentation Sculpturing or markings on a body or part.

Orthodromic Proceeding in the usual (direction).  Usually applied to nerve impulses but also to gonad direction in nematodes
Orthokinesis Variation in generalized, undirected, random locomotory activity caused by variations in the intensity of stimulation.
Oscillation One complete body swing from one extreme limit to the other of a nematode
serpentine movement.

Orthometaneme Filamentous organs located in or near lateral chord. See Metaneme.
Osmosis The tendency of two solutions to equalize by diffusion through a selectively permeable (semi-permeable) membrane. See euryhaline, stenohaline.
Outer Circlet The combined cephalic crown of papillae and the outer labial crown by forward migration of the former. The external circlet. See inner circlet. See Figure 2
, Figure 23..
Cuticular Layer This layer corresponds to the external and internal cortical layers of the cuticle. See cuticular layering. See Figure 21.
Outer Labial Sited on the distal lip segments.
Outer Labial Bristles Outer labial papillae which have altered to
bristle-like structures. The circlet is considered cephalic by some authors. See Figure 22,
Figure 23..
Outer Labial Papillae Sensory papillae situated distally on each lip segment forming a circlet of six in
primitive forms. The circlet is considered cephalic by some authors. See inner labial papillae.
Outer Leaf Crown The corona
radiata. See Figure12.
Outlet Valve The esophageal lumen at the junction of the
haustrulum with the esophageal- intestinal canal. See inlet valve. See Figure 15.
Outstretched Ovary Where all segments of the reproductive tube are in a straight line. See straight ovary,
recurved ovary, reflexed ovary. See Figure 27.
Oval Ellipsoidal. Having the outline of an egg.
Ovarium The ovary.
Ovary The reproductive organ of the female which produces the ova. See testis.
See Figure 25,
Figure 26, Figure 27.

Ovate Oval in shape with the broader end basal. See ovoid, obovate.
Ovejector Var. of ovijector.
Overall Application Broadcast application.
Ovic Juvenile Unhatched first stage larva contained within a deposited egg.
Ovic Embryo Term for eggs containing an embryo or larva. An embryonated egg.
Oviduct A tube which serves for the passage of ova from the ovary to the uterus. See
Figure 27.
Oviform Having the shape of an egg.
Egg-like. See ovoid, ovoidal.
Ovijector That portion of the oviduct modified to aid in the expulsion of the egg, generally heavily muscularized.
Oviparous Producing eggs that hatch after expulsion from the body. See
ovoviviparous, viviparous, larviparous, fissiporous, reproduction.
Oviposit To lay eggs.
Ovocyte An oocyte.
Ovoid Having a shape like an egg. See ovate.
Ovoid, ovoidal Having the shape of an egg. Egg-like. See ovate, oviform.
Ovoviviparous Producing thinly shelled eggs which hatch within the uterus.
Larviparous. See viviparous. oviparous, fissiparous, reproduction.
Ovum (
pl. Ova) The reproductive cell of the female nematode. An egg.
Oxyuroid Esophagus Having a cylindrical shape anteriorly and terminated by a basal bulb.
Also termed bulboid.

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Paddle-shaped See spatulate, remiform. spathulate.
Paedogenesis Reproduction in a larval stage. See neotony, reproduction.
Paedogenetic Reproducing in the larval stage.

Paedomorphism Evolutionary change in a charactyer that is exhibited in a juvenile stage.
Paired See

Palearctic Region That part of the Holarctic Realm considerd the Old World, which covers Asia. See Nearctic Region, Holarctic Realm.
Palmate Hand-shaped. Resembling a hand with the fingers spread.
Palps Specialized labial appendages, apparently for touching, grasping or guiding material to the mouth.
Panduriform Obovate with a concavity on either side much like a violin.
Papilla (pl. Papillae) Minute elevations of the cuticle. Any small nipple-like projection or part. In general sensory organs. See Figure 2
, Figure 5, Figure 11, Figure 22, Figure 23..
Papillary Nerves Six nerves, two
dorsolateral, two lateral, two ventrolateral from the nerve ring to the sense organs of the anterior end consisting of three circlets of sixteen members.
Paplliform Having the shape of a papilla.
Parahemizonid The hemizonion and similar structures.
Paralectotype All types remaining after selection of a lectotype
. See type.

Parallel Evolution Independent changes in a character that was identical in two different ancestors to a new charcater state that is the same in two descendants.

Paraphasmids Thick walled ampullae at the sites of the phasmids.

Paraphyletic Group A group of organisms with a common ancestor and most of the descendants of that ancestor, excluding  monophyletic subgroups that are descendants of a later ancesor in the group. See monophyletic, monophyly.

Paraphyly Exhibiting the paraphylectic condition. See monphyly
Parasite An
organism that obtains its sustenance wholly or in part from another living organism. See free-living feeding.
Parasitic Castration A situation where parasitic nematodes destroy the gonads or arrest their development, especially in insects.
Parasiticide Any agent lethal to parasites.
Parasitism An association where one individual lives at the expense of
another, makes no return and is destructive to its host. The state of being parasitic.

Paratenic Host  A substitute intermediate host in which the parasite feeds, but does not pass through developmental stages, until a Definituve Host is reached. See Definitive Host; Transfer Host..
Paratype All specimens remaining after the selection of the holotype and allotype. See type.

Paravulvae  Specialized ventral body pores in females, located anterior and posterior to vulva. See genus Paravulvus.
Parenteral Feeding The absorption of food other than by way of the intestine. See feeding.
Pars Distalis Vaginae The distal part of the vagina with cuticular lining contiuous with that of the exterior of the body. See Figure 35.

Pars Proximalis Vaginae The proximal section of the vaginal canal with hyaline walls. See Figure 35

Pars Refringens Vaginae The distal-intermediate section of the vaginal canal, sclerotized, refractive structures varying in shape. See Figure 35

Parthenogenesis The development of eggs without benefit of fertilization by spermatozoa. See Monogony, Reproduction, Sperm-dependent; Meiotic Parthenogenesis; Mitotic Parthenogenesis

Parthenogenetic Having the ability to reproduce by parthenogenesis. See Parthenogenesis.
Partial Sterilization An incorrect term for selective killing of organisms in a substrate.
See Pasteurization.
Partial Striae Intermediate striae.

Partite Parted. Separated.
Passive Migration The transport of nematodes by water, wind, on hoofs, feet and bodies of animals, the activities of man, etc.
Pasteurization The process of selectively killing a particular organism or group of organisms in a substrate leaving other organisms alive. See sterilization.
Patent Open. Spreading. Affording passage. Expanded. Distended. See patulous, prepatent.
Pathogen A disease causing agent.
Disease causing.

Pathogenicity The process of causing disease.

Pathological, Pathologic A diseased condition. A morbid state due to a disease. Unhealthy.
Pathology The study of disease, their nature, causes, etc.
Cuticular ornamentations.
Patulous Open. Spreading. Expanded. Distended. See patent.

PCR See polymerase chain reaction.
Pearls White
Heterodera cysts.
Pear-shaped See
piriform, pyriform.
Pea-shaped See
Pectinate-shaped like a comb. Having narrow parallel projections.
Peduncle A stem or stalk.
A stem-like structure supporting an organ or other structure.
Pedunculate Set on or attached by a slender stem or neck. Petiolate.
Pedunculate Papillae Genital papillae of male nematodes elevated on little stalks.
Pelagic Fauna The plankton and nekton animals of the open sea.

Pelagic Zone The open sea, especially beyond the littoral zone and above the abyssal zone.
Pellicle A thin membrane or film.
Peloderan Caudal alae which meet posterior to the tail. See leptoderan.
Pellucid Transparent.
Penetrate To pass beyond the surface.
To pass into or through a thing. To pierce. See lancinate.
Peppercorns Galls produced by some species of
Anguina, especially by A. tritici in wheat kernels, See cockles, purples.
Percutaneous Penetration through the skin.
Perforate To pierce. See
Perianal Situated or occurring around the anus.
Periaxial Surrounding an axis.
Peribuccal Around, enclosing or surrounding the buccal cavity.
Perienteric Fluid Fluid of the pseudocoel.
Perineal Belonging to the perineum.
Perineal Pattern Configurations, especially of Meloidogyne spp., on the cuticle surface of the perineum; specific designs are common to each species. See posterior cuticular pattern.
Perineum The superficial region about the anus.
Perioral Around, enclosing or surrounding the oral aperture.

Perioral Cuticle Cuticle of the lip region surrounding the oral aperture, often demarcated by ridges, incisures, flabella and cornua.  See flabellum, cornu.
Petaloid Having the form or appearance of a flower petal.
Petiolate Stalked. Situated upon a stalk.
pH A symbol of a scale used to designate the relative acidity of a solution. The scale ranges from 1 to 14. pH 7, the midpoint, represents a neutral solution. Numbers less than 7 indicate increasing acidity; those more than 7 increasing alkalinity.
Phagocyte A
coelomocytic cell which ingests or absorbs noxious organisms, tissue or detritus.
Phagocytosis The engulfing and destruction of microorganisms, tissues or detritus by phagocytic action.
Pharyngeal Bulb A muscular swelling of the esophageal wall around the
buccal capsule.
Pharyngeal Caecum The esophageal caecum.

Pharyngeal Collar See pharyngeal sleeve (preferred term)
Pharyngeal Glands The esophageal glands.

Pharyngeal Gland Nuclei and Orifices See Esophogeal Gland Nuclei and Orifices.

Pharyngeal Sleeve Extension of pharyngeal tissue surrounding the posterior part of the stoma

.Figure 40
Pharyngo-Intestinal Valve The esophageal-intestinal valve.
Pharynx The anterior part of the digestive tract with a tri-radiate lumen
. Variation of oesophagus or esophagus..
Pharynx Lumen The esophageal lumen.
Phasmidial Glands The precaudal glands.
Phasmids The lateral caudal papillae connected with the lateral precaudal glands. Paired postanal lateral chemoreceptor sensory organs. See precaudal glands, scutellum.
See Figure 19, Figure 29, Figure 41.
Phenotype The visible characters of an organism resulting from the interaction of genotypic
characters and environment. See genotype.

Pheromone Chemicals performing the function of hormones outside the body of the emitting individuals to to affect the behavior of the receiving individuals. See kairomone, allomone, synomone, semiochemical.
Phoresy A symbiotic relationship in which one organism transports another organism of a different species.  Often exhibited in arthropods and also in some fishes.

Phoretic Relationship  A symbiotic relationship in which one organism is transported by another.  See phoresy.

Phospholipid Fatty Acid Fatty acids derived from phospholipids which are the primary lipids of cell membranes.  Their analysis may be used to determine the composition of a microbial assemblage.

Photoautotroph An organism that  uses the energy from sunlight to build organic compounds.  See Autotroph, Chemoautotroph, Heterotroph.

Phyllophagous Feeding on leaves, See feeding.
Phylogenetic Relating to the lineage history of the development of a natural group.
Phylogeny The lineage history of the development of a genus, family, class or other natural group. See ontogeny, speciation.
Phylum (pl. Phyla)
In the systematic arrangement of organisms into groups or categories denoting natural relationships a category ranking above a class and below a kingdom. See classification.
Physiological Race, Physiologic Race See race, hostic race.
Phytocidal Lethal to plants. See phytotoxic.
Phytocide Any agent lethal to plants.
Phytonematode A plant parasitic neniatode.
Phytoparasite Nematodes capable of obtaining sustenance from plants.
Phytophagous Feeding on the tissues or juices of plants. Herbivorous. See feeding.
Phytotoxic Injurious or lethal to plants. See phytocide.
Phytoxic Phytotoxic.
Piercing Organ See stylet, odontia, jaws, spines, denticle, lancinate.
Pilliferous Hairy.
Pioneer A biotype.
A mutation or an adaptation through selection of a nematode population feeding on a nonhost.
Piriform Pear-shaped. See pyriform.
Pisiform Having the size and shape of a pea
Plankton Organisms that float and move passively with winds and currents, generally of microscopic size. See pelagic, nekton,
Plant-Inhabiting Nematodes Two different biological groups which can be distinguished as parasites and saprozoites. See feeding.
Plaques An inflated condition of the cuticle with the general appearance of looking like deep annulations divided longitudinally.
See inflation of the cuticle, warts.
Plate-like See disc, clintheriform.
Platymyarian A type of muscle cell between the hypodermal cords in which the muscle fibers are all adjacent to the hypodermis . The platymyarian meromyarian arrangement of somatic muscle cells is most common in nematodes.  See meromyarian, polymyarian, coelomyarian, circomyarian. See Figure 8.
Plectanes Cross striated cuticular plates which function to support genital papillae of some males.
Plectoid Having the characteristics of the genus Plectus.
Plesiotype A specimen upon which subsequent or additional description or figure is based. See type.

Plesiomorphy; Plesiomorphic Character or Trait A character that is unique to a group or species and that may have occurred near to that found in the ancestor; an ancestral trait.

PLFA See phospholipid fatty acid.
Plicate Bearing folds or parallel ridges. See ridge.
Plicatulate Minutely ridged.
The condition of being a multiple of a basic haploid number.

Phiricellular Many celled.
Point The apex of
anthing having a tapering end. See apex, mucro.
Pointed See
acunate, acute, acuminate, acurninose, cusp, aciforin, obtuse.
Polar Body One of the daughter nuclei derived from the first or second division of meiosis containing practically no cytoplasm and is expelled from the
Polar Filament A projection of the protein
membrane on some nematode eggs, probably serving in attachment.
Polydelphic Having three or more gonads. See amphidelphic. monodelphic, prodelphic, opisthodelphic, didelphic.
Polygamous Mating with two or more females. See reproduction.

Polymerase Chain Reaction, PCR Repeated heating and cooling thermal cycling that facilitates DNA melting and enzyme catalyzed DNA replication so that large quantities of a specific DNA sequence are produced in a short time. The process reuires Primers and DNA Polymerase.  See Primer, DNA Polymerase.
Polymorphic, Polymorphous Occurring in two or more forms. See dimorphic,
heteromorphic, monomorphic.
Polymyarian The presence of many rows of  longitudinal muscle cells between hypoderal cords; best viewed in transverse body section. See holomyarian, meromyarian.

Polyparaphyletic A paraphyletic groupin from which many monophyletic groups are exclyded. See polyphyletic, monophyletic.
Polyphagia The ability to subsist on various kinds of food. See feeding.
Polyphagous Feeding on many kinds of food, especially nematodes feeding on decaying organic matter. Plant pathogenic nematodes feeding on two or more hosts.

Polyphagy The ability of plant-pathogenic nematodes to subsist on two or more host plants. See feeding.
Polyphyletic Group Derived from two or more ancestral types, races, families, in which common characters are convergences from different ancestors. See monophyletic, paraphyletic.
Polyploid Having a chromosome number in multiples of the basic haploid number. See monoploid, aneuploid, euploid, heteroploid, hyperploid, diploid.
Polyploidy A
polyploid condition..
Polyxenic Pertaining to the rearing of an organism with many other known species of associated organisms. See gnotobiotic, agnotobiotic, xenic, axenic, synxenic, monoxenic, dixenic. trixenic.
Ponding A problem of puddling in applying large quantities of nematicide carrying liquids due to the compacting of the soil surface layers.
Population The individuals inhabiting a specific unit of substratum.
Population Density The number of individuals per unit of substratum.
Pore A minute opening or orifice; generally the outlet of a gland.
Pore Space The space within soils not occupied by solid particles.
Port Of Entry Point of penetration of a parasitic nematode through either natural or
unnatural openings.
Position The site of
attachment of an organ or part. See lateral, laterodorsal, dorsoventral, submedian, anteroposterior, dorsolateral, subdorsal, laterosubdorsal, subventral, ventrolateral, lateroventral, sublateral, dorsomedian, median, ventromedian, postanal, posterior, anterior, anteroventral, medioventral, preanal, postanal, lateroanal. anterodorsal. See Figure 22,
Figure 23..
Possum Ears A disease of strawberry incited by
Aphelenchoides fragariae. See dwarf.
Postanal Posterior to the anus. See position.
Postanal Pulvillus A satiation where the ventral cord passes o both sides of the rectum and is then continuous with swollen cells on the dorsal surface of the rectum.
Postalar Tail That segment of the tail posterior to the bursa.

Postcyclic Host In most cases non-hosts that have acquired a parasite (usually in the intestine) by prefation on the definitive host, intermediate hos or paratenic host. See Definitive Host, Intermediate Host, Paratenic Host.
Postembryonic Pertaining to the life stage after hatching from the egg.
Postembryonic Development Growth after hatching from the egg.
Posteriad Directed backward. Opposed to anteriad.
Posterior On or toward the hind end of a body or part. See anterior.

Posterior Adhesion Tube  A tube for sececreting adhesive material located in the poseterior region of the body. See adhesion tube.
Cephalic Crown A circlet of four sub- median setae or papillae located immediately posterior to the anterior cephalic crown or fused with it in some forms. See anterior cephalic crown, labial crown of papillac.
Cephalid The second cephalid at which the two median cords arise. See cephalids. See Figure I.
Posterior Cuticular Pattern The perineal pattern.
Posterior Uterine Branch The postvulvar uterine branch.
Post Mortem After death, especially an examination. See necropsy, antemortem.
Postrorse In a backward or downward direction. See antrorse. retrorse,

Postpudendal With genital tube posterior to vulva. See antepeduntal.
Postuterine A position posterior to the uterus.
Postuterine Rudiment The postvulval uterine branch.
Postuterine Sac See postvulval uterine sac.

Post-uterine Sac See  postvulval uterine sac.
Postvulvar Posterior to the vulva.
Postvulval Ganglion A ganglion which receives the paired ventral nerve cords at a point posterior of the vulva where fusion into a single nerve cord occurs.
Postvulval Rudiment The postvulvar uterine branch. Postvulvar Sac The postvulvar uterine branch.
Postvulval Uterine Branch A rudimentary extension of the posterior uterus, See
Figure 25.

Postvulval Uterine Sac A rudimentary extension of the posterior uterus which sometimes functions as a spermatheca, sometimes postuterine sac or postvulval sac.

Potato Sickness A disease of potato incited by Globodera rostochiensis.
Praeapical Glands The phasmids.
Praecaudal Glands Var. of precaudal glands.
Praecorpus Var. of procorpus.
Praerectum Var. of prerectum.
Preadult The last larval stage before becoming adult. Preanal Anterior to the anus. See position.
Preanal Ganglion A ganglion which receives the Ventral nerve cord and from which the anolumbar connectives extend to the lumbar ganglia.
Preanal Sucker A greatly enlarged genital papilla having a sucker-like form.
Preanal Tubes The cuticularized ducts of the preanal ventral glands.
Precaudal Glands Two organs situated in the lateral sectors of the tail. The openings to the exterior are termed the phasmids. Phasmidial glands.
Precociousness The presence of reproductive structures in
preadult forms. See neotony, paedogenesis, reproduction.
Predaceous Living by preying on other organisms.
See feeding.
Predacious Fungi
Fungi with the capacity to capture nematodes and derive sustenance from them.
Predator A nematode which lives by preying on other nematodes or organisms. See generalist predator, specialist predator.
Predigestion The digestion or partial digestion of food outside the intestine. See extraoral digestion, extracellular digestion, intracellular digestion.
Preferred Host A plant affording a more favorable environment to a nematode parasite than other suscepts.
Prepatent The condition or situation preceding the patent condition.
Preputal Fold A campanulate fold of cuticle directed posteriorly over the tail of some male forms.
Prerectum The segment of the alimentary tract between the intestine and the rectum, separated from the intestine by a stricture in the lumen and from the rectum by a sphincter muscle.
See Figure 18.
Pressure The stresses endured by a nematode population in its struggle for survival.
See stress.
Pressure Orifice System A method of applying liquid
nematicides to soil utilizing pressure, orifice diameter and tractor speed for various rates of application.
Primary Axil A cleft or depression between two lips that alternates with the spacing of the labial probola. There are two sub-dorsal and one ventral primary axils; the spaces may contain one or two guard processes. See secondary axil, guard process, labial probola, Figure 36.

Primary Muscle Fields The somatic muscles as divided into four main groups by the cords. The dorsosubmedian muscle fields and the ventrosubmedian muscle fields. See Figure 21.

Primer Short single-strand DNA fragments called oligonucleotides that are a complentary sequence to the traget DNA region to be amplified in the polymerase chain reaction. See Polymerase Chain Reaction.

Primitive Character Persisting in structure little advanced from ancestral form. See primordial, plesiomorphic, derived character.
Primordial Growth of an individual or organ in its earliest or primitive form.

Primordial Germ Cell Cell at begginning of ovary where divison of oggonia is initiated.  See Cap Cell.
Primordium (pl. Primordia) The initial development of an organ, tissue or individual.
Probolae Prominent and elaborate specialized extensions encircling the oral aperture especially in cephalobids; situated in some nematode forms in labial and cephalic positions. See pseudolabia, cephalic tubers. labial probola. See Figure 11, Figure 36.
Process A prominence or prolongation of a surface.
An outgrowth or extension. See apophysis, corniform, excrescence.
Procorpus Tue anterior subdivision of the corpus taking a cylindrical form and generally being terminated by an oval posterior segment. See metacorpus
. See Figure 1.
Proctodaeum The invagination of the epiblast that produces the anus and intestine.
Prodelphic Having a single ovary anterior to the vulva. See amphidelphic, monodelphic, opisthodelphic. See Figure 25.
Progeny Offspring. Young. See reproduction. Prolate Elongated, s a spheroid stretched out in the direction of the two opposite poles. Lemon-shaped.
Proliferative Cell
The terminal cell.
Stylet extensions.

Promoter A DNA sequence to which proteins and RNA polymerase bind that initiate transcription of RNA from the downstream DNA. See RNA Polymerase.
Pronucleus (pl. Pronuclei) A gamete nucleus after maturation is completed. Two haploid gamete pronuclei fuse to form a diploid zygote nucleus in fertilization.
Propagate To continue or mult
iply by bearing young, seeds or cuttings and the like. See reproduction.
Prophase The initial stage of mitosis or meiosis in which chromosomes appear. See metaphase, anaphase,
Prorhabdions Walls of the prostom
. See Figure 1, Figure 10.
Prostatic Glands Glands in some male nematodes which produce an adhesive secretion at the distal end of the ejaculatory duct.
Prostegostom The most anterior region of the stegostom, the prostom.

Prostom The anterior subdivision of the protostom. See mesostom, metastom. See Figure 10.
Protandrous Hermaphroditism Spermatozoa and later ova are produced by the same gonad. A syngonic female. See reproduction.
The production of spermatozoa and later ova by the same gonad. See reproduction.
Protein A very complex organic compound built of numerous amino acids and which form an
essential part of the structure and diet of all animals. Protein contains nitrogen, carbon, hydrogen, oxygen and usually sulfur.

Protein Membrane The outer covering of the egg surface sculpturing of some and it is deposited by the uterine wall.

Proteome The complete set of proteins produced in a cell.

Proteomics The systematic large-scale analysis of proteins of a cell or system.
Proterotype The primary type which includes all the material upon which the original description is based. See type.
Protoplasm The basic substance of which all living matter is
made, being grayish, semitransparent, viscid and a complex colloidal physiochemical system that constitutes tile living matter of plant and animal cells.
Protorhabdions The walls of the protostom.
See Figure 1, Figure 10.
Protostom The middle region of the stoma delimited anteriorly by the cheilostom and posteriorly by the telostom. The protostom is subdivisible into three parts: the prostom, mesostom and metastom. See Figure 10, Figure 40..
Protostoma Var. of protostom.
Protract To extend or
Gubernaculi Paired gubernacular muscles which extend from the subventral body wall anterior to the proximal part of the gubernaculum. See gubernacular muscles.
Protractor Muscle A muscle which functions to extend an organ. See Figure 5.
Protractor Onchii The protractor muscle of the stylet.
Spiculi Paired spicular muscles extending obliquely from the spicules to the ventral side of the body. See spicular muscles.
Protractores Spiculorum See protractor spiculi.

Protuberance An elevation above the surface, A protrusion or bulge.
Prouterus A situation where the proximal end of the uterus is separate and may function as a receptacle or shell gland.

Provisioning Services Ecosystem services that provide products whicht support or maintain life.  For example, food, fiber, fuel, energy, pharmaceuticals.
Proximad Toward the proximal end.
Proximal Designating that end of a part or organ nearest to the point of attachment or origin.

Psammal A sandy soil environment or habitat.
Pseudobulb A swelling of the esophageal musculature in which the lumen does not widen to form a cavity. A nonvalvate esophageal bulb. See true bulb.
Pseudocoel The pseudocoelom.
Pseudocoel Cells Coelomocytes.
Pseuocoelocytes Coelomocytes.
Pseudocoelom The body cavity of the nematode. See pseudocoelomic membranes, mesenteries, coelomocytes, body cavity.

Pseudocoelomate Possessing a body cavity that is not entirely surrounded by mesoderm.
Pseudocoelomic Membrane A delicate sheath which invests and supports the internal organs, specifically it surrounds the esophagus, lines the internal surface of muscle cells and extends between each pair of muscle cells to the hypodermis. See mesenteries. isolation

Pseudogamy Activation of development of an oocyte by a sperm without nuclear fusion, also known as sperm-dependent parthenogenesis. In most cases of pseudogamy, the sperm is obtained by copulation with other species. See Sperm-dependent Parthenogenesis, Auto-Pseudogamy..
Pseudolabia Prominences of the head often elaborately developed. They are situated in labial and cephalic positions in some nematode forms. See probolae, cephalic tubers.
Pseudonchs Structures in the pharynx which resemble onchia in certain views.
Pulvillus A cushion-like group of cells. See postanal pulvillus.
Punctations Small pits or deep depressions on the surface of the cuticle; the shape is usually rounded but may wary.
Purples Galls produced by some species of
Anguina, especially by A. tritici of wheat kernels. See cockles, peppercorns.
Pure Culture A nematode population containing a single species only; it differs from aseptic culture by not being free of other organisms.
See pure population, agnotobiotic culture, monoxenic culture. axenic culture, pure line population.
Pure Line Population A nematode population derived from a single parent or set of parents.
Pure Population A nematode population containing a single species only; it differs from aseptic population by not being free of other organisms.

PUS See postvulval uterine sac.
Pustule A small papilliform or blister-like elevation.
Putrifaction The process of organic decomposition especially the anerohic breakdown of proteins.
Pyriform Pear-shaped. See piriform.

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Quadricolumella In the female gonad probably the gland region that secretes the egg shell. See Crustaformeria.
Quarantine A restraint upon goods, animals, plants or other materials which may bear pathogenic organisms.

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Race A hiotype or groups of biotypes which differ from one another in certain physiological characters which function to segment the species into subspeciflc categories. A population which reacts differently than other populations of apparently the same species. See hostic race.
Rachis An axial structure or column.
Radial Developed or situated around a central axis.
See actiniform.
Radial Bars In the cephalic framework six rigid supports connecting the vestibule of the stylet guide and the basal ring and ribs. See Figure 6.
Radial Blades The radial bars.
Radial In Form See actiniform, stellate, triradiate.
Radial Muscles
Muscles of the esophagus which dilate the lumen of the esophagus.
Ramified Branched..
Ramiform Resembling or-shaped like branches, Ramified

Random Movement Having a haphazard course or direction in contrast to a tactic response. See taxis.
Rapacious Feeding on prey.
Predaceous. Voracious. See feeding.
Rays Genital papillac and their accompanying muscles embedded in the bursa of some nematode forms.
The esophageal radii.

rDNA Ribosomal DNA are sequences encoding for ribosomal RNA and which regulate transcription of DNA to RNA. They contain transcribed and nontranscribed spacer segments. See DNA, RNA.  18S rDNA is the ribosomal DNA sequence containing genes that encode for ribosomal RNA (See rRNA). Sequence data from these genes is widely used in molecular analysis to reconstruct the evolutionary history of organisms as it is conserved and considered suitable for constructing evolutionary divergences.

Receptaculum Seminis The spermatheca.
Reciprocally Infective Capable of transferring from one crop to another then return to infect the original crop.
Commissure A commissure arising from the preanal ganglion and extending to the dorsorectal nerve.
Rectal Cuticle The cuticular lining of the rectum which differs in some respects from the external cuticle. See external cuticle, esophageal cuticle, cloacal cuticle, vaginal cuticle.
Rectal Glands Large unicellular glands, usually three in females and six in males.
Rectal Matrix Glands See matrix glands.
Rectal Muscles Specialized muscles which function to widen the anal opening and are attached to the dorsal wall of the rectum.
Rectal Sinus A cavity immediately
anterior to the anus and to which the rectum is connected. See Figure 28.
Rectilinear Formed of straight lines or
characterized by straight lines.
Rectum A narrow
tube, flattened in dorsoventral direction and separated from the intestine by a sphincter muscle. It is derived as an invagination of the epidermis and is lined by a cuticularized intima. The hindgut. See cloaca
. See Figure 18, Figure 41 .
Recurved Reflexed.
Recurved Ovary A situation where the distal portion of the gonoduct is turned back on itself. Recurved ovaries are considered to belong to the more primitive
type of ovary. See outstretched ovary. See Figure 26, Figure 27.
Red Plant A disease of strawberry incited by
Aphelenchoides fragariae.
Red Ring A disease of coconut palm incited by Bursaphelenchus (Rhadinaphelenchus) cocophilus.
Reduction Division See meiosis.
Turned or folded back upon itself, especially applied to configuration of ovaries and testes of nematodes. See Figure 26, Figure 27.
Regenerative Power The ability to heal wounds.

Regulating Services Ecosystem services that regulate other ecosystem processes.  For example, activities and abundance of pest and disease organisms, decomposition of organic wastes, purification of water and air.
Relax To inactivate
nematodes, generally by heat prior to fixing. To kill.
Remiform Having a shape like an oar. See spatulate, spathulate.
Renette Generally one but, in some forms, two ventral excretory cells. The excretory gland.
Reniform Having the shape of a kidney.
Replacement Spear
Present in juvenileDorylaimoidea. Located in the anterior, slender portion of the esophagus..

Reproduction The process of perpetuating the species by giving rise to offspring. See neotony, paedogenesis, monogony, parthenogenesis, digonic hermaphrodite, syngonic female, syngony, protandrous hermaphroditism, syngenesis, polygamous, progeny, protandry, sex determination, sexual dimorphism, syngenesis. androgynous, dioecious, diorchic, monorchic, dimorphic, hermaphrodite, precocious, monogenetic, hetero genetic fissiparous, bisexual, gyandromorph,, heteronomy, larviparous, ovoviviparious viviparous, oviparious, monogenesis.
Reproductive System All the organs and structures concerned in the production and delivery of ova and sperm.
Reservoir A plant parasitic nematode population surviving on a "weed" host.
A cavity or ampulla for the storage of a fluid or secretion.
Resistance The ability of an organism to remain relatively unaffected by a disease due to possession of certain inherent properties. A host may be slightly, moderately or highly resistant.
The reduced rate of parasite reproduction on a host.
Resistant Stage That period of a nematode life cycle in which environmental extremes have little or no affect.
Resister The species biotype capable of withstanding the adverse affects of parasites, climate, resistant hosts, etc.
Respiration The absorption of oxygen from the surrounding medium and giving off carbon dioxide and other products formed by oxidation in the tissues.
Restiform Corded or cord-like.
Reticulate Having cross markings like a net.
Rectractor Gubernaculi Muscles extending from the distal part of the gubernaculum to the dorsal or lateral walls of the body.
Retractor Muscle Muscles which serve to return an organ to its original position. See Figure 5.
Spiculi Paired muscles extending from the manubrium of the spicule anteriorly to the hypodermis near the lateral cords. See spicular
muscles. See Figure 5.
Retroarcuate Curved backwards.
Retrocession A recession or movement backward.
Retrogressive Development A simplifying evolutionary trend of an organism usually expressed as the complete or partial loss or amalgamation of structures.
Retrorse In a backward or downward direction.
Retrovesicular Ganglion The union immediately posterior to the excretory pore where the dorsolateral
nerves fuse.

Reviviscent Capable of reviving, especially some nematode forms after a period of desiccation.
Rhabdions The thickened curticular walls of the stoma. See cheilorhabdions, protorhabdions, telorhabdions.
See Figure 1, Figure 10.
Rhabditiform Having the shape of a rod.
Rhabditoid Having characteristics of the genus Rhabditis.
Rhabditoid Bursa A condition where the caudal alae meet posteriorly and anteriorly forming a complete oval. A wide caudal bursa.
Rhabditoid Esophagus Antcriorly of a cylindrical shape, often with a pseudobulb, followed by the isthmus and terminated with a basal bulb.
Rheophile Inhabiting rivers and streams. See hypogaeic, aquatic. edaphic, marine, terrestrial, terricolous, xerophilous, cavernicolous, fossorial, arenicolous, xiphilous.
Rheotaxis A situation where the tactic response is dependent upon the mechanical stimulation of a moving fluid, especially water, for the directive factor. See taxis.
Rheotropism A situation where the tropism is dependent upon the mechanical stimulation of a moving fluid, especially water, for the orientating factor. See tropism.
Rhizosphere The area immediately surrounding
the plant roots.

Ribonucleic Acid See RNA

Ribosomal DNA See rDNA.

Ribosomal RNA See rRNA.

Ribosome  The cell structure that is the site of protein synthesis. Ribosomal RNA (See rRNA) decodes messenger RNA (See mRNA) into amino acids
Ribs In the cephalic framework, six rigid supporting structures radiating transversely, then posteriorly to fuse with the anterior edge of the basal ring and the six radial bars. Four ribs are sublateral, one dorsal and one ventral. See basal ring, radial bars, cephahc arches. See Figure 6.
Ridge A raised line or strip on a surface.
See annulate. annulose.
Ring Nematode Decline Of Carnation A disease of carnations incited by
Mesocriconema xenoplax.
Ring-shaped See circinate.
Ripe Pertaining to mature ova or spermatozoa.
River Inhabiting
See rheophile

RNA Ribonucleic acid. A nucleic acid consisting of a chain of nucleotide units, each with  a nitrogenous base, a ribose sugar and a phosphate.  Usually single stranded.  Differs from DNA which is double stranded, in which the sugar is deoxyribose, and( has thymine rather than uracil as a nucleotide. RNA is transcribed from DNA by RNA polymerase enzymes. See DNA.

RNAi RNA interference. A mechanism inhibiting gene expression or or by hindering gene transcription.  See RNA.

rRNA  Ribosomal ribonucleic acid is the RNA component of the ribosome (See ribosome).  It provides a mechanism for decoding messenger RNA (See mRNA) into amino acids by interacting with transfer RNA (See tRNA) which transfers the amino acids that correspond to the mRNA codon.  18S rRNA is the structural RNA which codes for the small subunit of ribosomes in eukaryotes.  The genes coding for 18S rRNA are referred to as 18S rDNA (See rDNA).

RNA Polymerase An enzyme that synthesizes RNA from a DNA template.

Rod Border Structures on intestinal epithelium which are probably modified immobilized cilia.
Rod-like See baculiform, rhabditiform.
Rogue To remove undesired individual plants from a crop.
Root Ball The interwoven network of plant roots of a potted plant.
Diffusate A root excretion that affects the behavior of plant parasitic nematodes, especially as a hatching or tactic stimulus, See leachate
Root Galls A pronounced localized swelling of root tissue due to hypertrophy and hyperplasia incited by nematode feeding.

Root-Knot Index An index of the amount of root galling as a measure of the Meloidogyne population:
1 = zero percent roots galled
2 = 1 to 25 percent galled
3 = 26 to 50 percent galled
4 = 51 to 75 percent galled
5 = 76 to 100 percent galled
nematode index.
Rootlet A small root.
Root Rot Complex A morbid condition of roots and root tissues incited by multiple attacks of nematodes, fungi, bacteria, etc,
in stages or nearly simultaneously.
Root Zone
See rhizosphere.
Rosette A pathological condition where the internodes of plants are shortened and the normally separated leaves are closely clustered.
Rosette The
uvette of the deManian system.
Punctation patterns of the cuticle surrounding genital papillae.
Rostrum (pl.
Rostra) A beak-like projection ventrad near the proximal end of thespicule, joining the dorsal and ventral spicular shafts.
Rot Destruction of tissues by decay organisms; frequently after nematode injury.
Roundworm A vernacular term for any individual of the phylum
Nematoda, especially as applied to parasites of vertebrates. See eelworm, nema, nematode. threadworm.
Row Application The placing
of a nematicide in such a manner that the lethal vapor is effective in a broad band where the future row crop is to be planted. See broadcast application, spot application, drench application, gas application.
Rudimentary A condition of imperfect development.
Development on a primitive level. Development arrested at an early stage. Vestigial.
Rudimentary Posterior Uterine Branch A vestigial extension of the posterior uterus.
A postvulvar uterine branch.
Rudimentary Posterior Uterus A vestigial extension of the posterior uterus.
A postvulvar uterine branch.
Rugae Ridges formed by folds in the wall of a structure. See Buccal Rugae

Rugose Wrinkled.
Rugosissimus Extremely rugose or wrinkled.
Rugula (pl. Rugulae) A small wrinkle.
Rugulose Having fine wrinkles.
Rypophagous Rhypophagus Filth-eating. See feeding.

Return to Dictionary Index



Sac A bag or sack-like structure. A pouch.
Saccate Sac-shaped. Contained in a sac.
Sacciform Having the shape of a sac.
Saccular Sac-like.
Saccule A small sac or pouch.
Sack-like See sac.
Sagittate Arrowhead-shaped. Triangular-elongate.

Sagittal Plane The median-vertical-longitudinal plane in a bilaterally symmetrical animal or a section parallel to that plane. See longitudinal plane, transverse plane.
Sagittiform Arrowhead-shaped.
Saint John's Disease A disease of peas incited by Heterodera goettingiana.

Salient Pointing outwards, noticeable, obvious.
Saliva A secretion o the esophageal glands presumably containing a digestive enzyme.
Salivary Gland The esophageal glands. See
Figure 3.
Sand Individual rock or mineral fragments in soils having diameters ranging from 0.5 mm. to 2.0 mm. Usually sand grains consist chiefly of quartz but they may be of any mineral composition. The textural class name of any soil that contains 85 percent or more of sand and not more than 10 percent of clay.
Sand Inhabiting See arenicolous.
Sandy Clay Soils of this textural class contain 35 percent or more of clay and 45 percent or more of sand.
Sandy Clay Loam Soils of this textural class contain 20 to 35 percent clay, less than 28 percent silt and 45 percent or more of sand.
Sandy Loam Soils of this textural class have 50 percent sand and less that 20 percent clay.
Sap The juices of a plant cell.
The semiliquid constituents which compose the protoplasm of the plant cell. The watery solution which circulates through plant vascular tissue.
Saprobiont An organism which subsists as a saprophyte or saprozoite. See saprophage, feeding.
Saprophage An organism which derives its sustenance from decaying organic matter. See feeding.
Saprophagous Feeding on dead or decaying organic matter. See feeding.
Saprophyte Any organism deriving sustenance from dead or decaying organic matter. See feeding.
Saprozoic Pertaining to an animal which derives sustenance from dead or decaying organic matter. See feeding.
Saprozoite An animal which derives its sustenance from dead or decaying organic matter. See feeding.
Sarcophagous Flesh eating. See Feeding.
Sarcoplasm The undifferentiated protoplasm of the muscle cell. See fibroplasm. See Figure 8
, Figure 9.
Scaffold An abnormally heavy, refractive guiding ring.
Scalariform Bearing markings like the rounds of a ladder.
See imbricate.
Scalloped See crenate.

Scaphiform Having the shape of a boat.
Scavenger An organism which derives sustenance from the refuse, offal and decaying matter of other life,
See feeding.
Sclerite A hard plate or piece of cuticle.
Sclerotized A noncommittal term for hardened. dense, refractive parts of the nematode body.

Sclerotized Vagina See Pars refringens vagianae.
Sculate Having the shape of a shield. See scutiform, escutcheon-shaped. clypeiform.
Scutellate Having a surface divided into small plate-like areas.
Scutellum (pl. Scutella) Greatly enlarged phasmids common to some species of the Hoplolaiminae.
See Figure 19.
Scutiform Having the shape of a shield. See scutate, escutcheon-shaped, cypeiform.

S-E Pore Secretory-Excretory pore. See excretory pore, cervical pore.
Second Bulb The terminal bulb.

Secondary Axil A cleft or depression between two lips that is in line with a labial probola. There is one dorsal and two sub-ventral asecondary axils, they are usually broader and shallower than the primary axils. See primary axil, labial probola, Figure 36.
Secondary Invaders Any and all organisms found in a host after the initial attack and injury by the primary parasite.

Secondary Host The host in which the asexual stages of a parasitic life cycle take place. See Intermediate Host.
Secretion A useful product produced by a cell or gland.
The act of producing or passage of this product. See excretion.
Sector The interval between the cords.
Sedentary Endoparasite See sedentary nematodes.
Sedentary Nematodes
Nematodes which become established within or on the roots of host plants i.e. root-knot, cyst-forming, Cobb's root- knot, reniform, etc., where the females remain fixed in position throughout their life cycle.

Sediment Particulate meterial, organic and inorganic, that settles to the bottomof a body of water and may provide habitat and resources for organisms.

Sedimentary Layer See Sediment.
Seductor Gubernaculi Paired muscles extending from the proximal end of the gubernaculum to the dorsolateral walls of the body.
Seed Galls Enlarged ovules converted to a gall and containing nematode larvae, especially on grasses and cereals.
Segging In Oats A disease of oats incited by Ditylenchus dipsaci. See tulip root.
The repetition of elements of the main organ systems of the body along the length of the body.  For example, in the earthworms (Annelida), each of the externally visible rings marks a segment (or metamere) of the body that contains a similar pattern of blood vessels, nerves, excretory organs, external features, etc.; similar patterns are evident in Arthropoda.  In the Vertebrata, segmentation is most obvious during embryonic development; in adults it is confined to mesoderm derivatives such as muscle and skeleton, e.g., repetition of vertebrae and ribs.

In embryological development the subdivision of the single-celled egg into blastomeres. Cleavage.

Seinhorst Extraction Technique A method for the isolation of nematodes from infected plant  material utilizing funnels, a constant fresh water spray and suitable settling basins.
Seinhorst Elutriator Apparatus An apparatus employed for the isolation of nematodes from soil resulting in a sample relatively free of debris.
Seinhorst Technique An elutriation method for quantitative extraction of nematodes from soil.
Seleniform Having the shape of a full moon.

SEM Scanning electron microscope or scanning electron microscopy.

Semelparity A species is considered semelparous if it is characterized by a single reproductive episode before death. See Iteroparity.
Semifenestrate A situation in some species of the genus Heterodera where the vulval bridge divides the fenestra into two parts. See fenestrate, bifenestrate, ambifenestrate, circumfenenstrate. See Figure 31, Figure 32.

Semilunar Having the shape of a halfmoon.
Seminal Receptacle The spermatheca.
Seminal vesicle
In male nematodes enlarged tube- or pouch-like structures which function to store the semen.

Semiochemical A chemical substance or substances released by an organism that affects the behaviors of individuals of the same or of other species. See pheromone, kairomone, allomone, synomone.. 
Semivagrant Nematode forms with mobile larval stages and sedentary parasitic adults.
Senescence Old. Aged.
Senility Old age. Passed the reproductive stage.

Sensilla Basiconica Cone or peg-shaped sensilla.
Sensilla Pouch An expansion of the amphidial tube containing the sensory elements of the sensilla and is situated posterior to the amphidial pouch. See Figure 2.
Sensillum (pl. Sensilla) A simple sense organ, or one of the structural components of a compound sense organ. The nerve ending connected with the amphidial nerve. See Figure 2.
Sensory Elements Stimuli preceptors collectively making up the
Sensory Organ A body structure which functions as a preceptor of stimuli.
Sepsis The state or condition of being septic.
See asepsis.
Septentrional Northern. Boreal.
Septic Contaminated with
microorganisms. - See aseptic.
Septicemia A morbid condition caused by pathogenic bacteria and their toxins within the body.
Seriate Occurring in a series or periodically.
Having marginal teeth or notches. See dentate.
Sessile Obligate feeding and reproducing at one fixed site. Not free to move from one site to another.
Seta (pl. Setae) Tactile sensory organs of elongate cuticular structure and articulate with the cuticle proper. A bristle-like protuberance. An aciculum. See tubiform setae, ambulatory setae, bristle setae, adhesion tubes.
Setaceous Bearing setae.
See setose.
Setiform Having the form of a seta. Bristle-shaped.
Setose Bearing setae.
Sex-Determination The factor or factors which cause the development of an egg into a male or female nematode. See reproduction.
Sex Ratio The proportion of males to females in a nematode population.
Sexual Dimorphism A difference in form or
stricture as males and females of the same species.
Sexual Reproduction Reproduction requiring tile union of male and female gametes. See asexual reproduction, syngenesis.
Shaft The main body of the
, usually

curved and often bearing a thin flange of cuticle termed the velum. See Figure 16.
Sheath A covering enclosing a body, part or
organ and generally elongated in form.
Shields Interlabia.
See scutate, scutiform, escutcheon-shaped, clypeiform.
See falcate, crescentiform, falciform.
Sieve-like See cribriform.
Sigmoid A two directional curve-shaped like the letter S.

Signal Peptide A short peptide (usually 16-30 amino acid) to which newly synthesized proteins, that are destined for secretory pathways, are attached. They prompt the cell to translocate the protein towards the cell membrane.
Silt Individual mineral particles of soil that range in
diameter between the upper size of clay, 0.002 mm., and the lower size of very fine
sand, 0.05 mm. Soil of the textural class silt contains 80 percent or more of silt and less than 12 percent of clay.
Silt Loam Soil material having 50 percent or more of silt and 12 to 27 percent of clay or 50 to 80 percent of silt and less than 12 percent of clay.
Silty Clay Soil of this textural class has 40 percent or more of clay and 40 percent or more or silt.
Silty Clay Loam Soil of this textural class has 27 to 40 percent of clay and less than 20 percent F of sand.
Single Egg Mass Line A nematode population derived from eggs produced by a single female.
See pure line population, single larva line, pure population, pure culture.
Larva Line A nematode population derived from an individual juvenile nematode.
Sinuate Wavy.
Sinuous Having a serpentine or undulant form.
Sinus A curvilinear indentation.
An opening or depression. A cavity, See antrum.
Sinus Canals Greatly enlarged ducts.
Sinusoidal Wavy, serpentine, winding in form.
Skeletal Fibrils The longitudinal and transverse fibrils of muscle cells.
Skeleton The cuticle to which the musculature is attached.
Skin The cuticle.
Skin Glands See lateral glands, cephalic glands, cervical glands,
preanal tubes, cement glands, hypodermal glands.
Slimeflux Wound sap of trees.
Slow Decline A disease of
citrus incited by Tylenchulus semipenetrans.
Soft Cuticle A gelatinous, elastic, extensible material that makes up most of the nematode body covering. See hard cuticle.
Soil Borne Nematodes living within the confines of the soil during at least part of their infective stage.
Soil Chimney Any passage leading to the soil surface allowing
nematicidal vapors to become diluted and escape.
Soil Fumigation The use of a nematicide to disinfest soil of plant parasitic nematodes.
Soil Inhabiting See
edaphic, hypogeal, terrestrial, terricolous.
Soil Mass Application The fumigation of soil in depth as contrasted to a surface application.
Soil Porosity The degree to which the soil mass is permeated with pores or cavities. Porosity can be generally expressed as a percentage of the whole volume of a soil that is unoccupied by solid particles. in addition, the number, sizes, shapes and distribution of the voids is important, Generally, the pore space of surface soil is less than one-half of the soil mass by volume, but in some soils it is more than half The part of the pore space that consists of small pores that hold water by capillary is called capillary porosity. The part that consists of larger pores that do not hold water by capillary and allows free drainage is called
non-capillary porosity.
Sterilant A nematicide with a broad lethal I spectrum i.e. will control nematodes, fungi, weeds, etc. See control.
Soil Structure The arrangement of primary soil particles into compound particles or clusters that are separate from adjoining aggregates and have properties unlike those of an equal mass of
unaggregated primary soil particles. The principal forms of soil structure are platy, prismatic, columnar (prisms with rounded tops), blocky (angular or subangular), and granular. Structureless soils are single grain (each grain by itself, as in dune sand) or massive (the particles adhering together without any regular cleavage as in many claypans and hardpans.
Soil Texture The relative
proportions of the various size groups of individual soil grains in a mass of soil. Specifically, it refers to the proportions of sand, silt and clay.
Soil Type A category under soil series based on the texture of the surface soil. See textural class.
Sole The site of attachment of the special ambulatory setae or adhesion tubes.
Solid Application The treatment of soil with a nematicide in such a manner that the expanding vapor forms a solid carpet throughout the field. Broadcast application See row application, drench application, gas application.
Solubilization A form of colloidal solution where a relatively insoluble chemical is dispersed in the form of micelles, consisting of alternating molecules of detergent and water with the inner core being the chemical.
Soma (pl,
Somata) The
body proper of an animal as distinguished from the germ cells. Alternatively, the portion of a cell that contains the nucleus.

Somatic Muscle Muscles of the body proper as distinguished from muscles of special function. Somatic muscles are grouped between the hypodermal cords; contractile regions are close to the hypodermis (platymyarian). There may be 2-5 rows of muscle cells betwwen the hypodermal cords (meromyarian) of  a large number of rows of muscle cells (polymyarian). See Figure 21.
Somatic Cells Body cells of an individual as distinguished from germ cells.
Somatic Setae The setae in general on the body cuticle as distinguished from cephalic setae, caudal setae, etc..
Somato-Esophageal Muscles Specialize muscles common to the esophageal region though of diverse form and origin.
Somato-Intestinal Muscles Specialize muscles common to the region of the intestine which extend from the body wall to the intestine.
Sorb To take up and retain by adsorption or absorption.
Sorption The act or process of sorbing. A general term covering adsorption and absorption.
Spathulate Paddle-shaped. Narrow and flat at the base and broad at the top. See reniforrn,