Criconematoidea Taylor, 1936
Criconematina (Siddiqi, 1980)
Hemicycliophoroidea (Skarbilovich, 1959)
Tylenchocriconematoidea (Raski & Siddiqui, 1975)
Characteristics Chart of the Order Tylenchida
Criconematidae Taylor, 1936
Morphology and Anatomy:
- Usually under 1 mm long, but longer in a few cases (up to 1.9 mm in Hemicycliophorinae).
- Marked sexual dimorphism; male slender, female sausage-shaped, cylindrical or spheroid.
- Female and juvenile with extremely variable cuticle; thick with retrorse annuli, lacking
may have lobes, crenation, spines, scales; or thick with smooth, coarse, rounded annuli covered or not with an extra-cuticular layer; or thin cuticle with fine rounded annuli and lateral fields often marked with lines (obliterated in swollen stages).
- Labial area in female and juvenile with usually one or two often modified annuli; oral aperture dorso-ventrally longitudinal on a raised area or labial disc.
- Basically, there are six pseudolips of which the four submedian ones can bear each a submedian lobe; no sensillae visible on surface of lip area. Labial framework hexaradiate, with light to strong sclerotization.
- Amphid openings round to oval, close to labial disc area.
- Phasmids absent.
- Females and most juveniles with well-developed stylet, often very long, with cone markedly longer than the shaft; basal knobs well-developed, either sloping backwards or anchor-shaped.
- Female and juvenile esophagus with median bulb enormously developed, muscular, containing a large, often elongated cuticular valvular apparatus and being amalgamated with
procorpus, which is usually broad and surrounds the basal region of the stylet;
Isthmus short, broad and amalgamated
with postcorpus bulb.
- Postcorpus small, offset from intestine (except in
Sphaeronema whittoni and
Meloidoderita kirjanovae in which the glands are free).
- Orifice or dorsal esophageal gland at a short distance (usually under 4 µm) behind stylet base.
- Vulva transversely oval or slit-like, located posteriorly, usually at over 75% of body length.
- Female genital tract has one branch, anterior, outstretched (may be coiled in swollen females).
- Post-vulval uterine sac absent. In juveniles, female genital primordium shows no element of a posterior branch.
- Spermatheca usually offset and inclined laterally or ventrally.
- Uterus with a distinct columned part, but number of rows of cells apparently not constant; in swollen females
vagina can have a thickened wall, transformed into a cyst in
- Intestine syncytial, lacking a definite lumen, often
extending beyond anus.
- Small, slender.
- Cuticle thin, with narrow annuli; no extra-cuticular layer; typical lateral field present.
- Stylet mostly absent or degenerated and non-functional.
- Esophagus degenerated, nonfunctional.
- One testis.
- Spicules often very long and setaceous, with small narrow head, elongate-slender shaft and finely pointed distal end; variable in shape, but often arcuate.
- Gubernaculum linear or crescent-shaped in lateral view, not protrusible.
- Caudal alae, when present, usually low, rarely
peloderan; but well-developed,
Tylenchocriconematinae and most Hemicycliophorinae.
- cloacal lips usually narrow and elevated, or drawn out as a penial tube.
- Hypotygma may be present or absent.
The Criconematoidea is widely considered a monophyletic group based on the
structure of the pharynx, sexual dimorphism, a monoprodelphic ovary without a
post vulva sac, and loss of phasmids and deirids (Andrássy, 2007;
Powers et al., 2017) with some opinion differences at the taxonomic level
Andrassy, I. 2007. Free-living Nematodes of Hungary
II. Hungarian Natural History Museum, Budapest. 496 p.
Powers, T., Harris, T., Higgins, R., Mullin, P. Powers, K. 2017. An 18S rDNA
Perspective on the Classification of Criconematoidea. J. Nematology 49:236-244.
Raski & Luc, Rev. Nematol. 10(4):409-444 (1987)
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