Family CRICONEMATIDAE

                                  Rev 07/11/22

Classification:

      Tylenchida
       Tylenchina
        Criconematoidea
         Criconematidae Taylor, 1936
    Synonyms:
      Macroposthoniidae (Skarbilovich, 1959)
      Madinematidae (Khan, Chawla & Saha, 1975)
      Criconematoidea (Siddiqi, 1980)
      Caloosiidae (Siddiqi, 1980)
      Hemicycliophoridae (Skarbilovich, 1959)

Per Geraert (2010) the family is separated into five subfamilies which inlcude about 18 genera and around 400 valid species.

Subfamily Criconematinae	Subfamily Macroposthoniinae	Subfamily Discocriconemellinae
Criconema Croserinema Crossonema Lobocriconema Neolobocriconema Ogma Orphreyus Pateracephalanema	Bakernema Criconemoides Mesocriconema Nothocriconemoides	Discocriconemella Xenocriconemella
Subfamily Blandicephalanematinae	Subfamily Hemicriconemoidinae
Amphisbaenema Blandicephalanema	Hemicriconemoides

Morphology and Amatomy:

      All stages:

•  vermiform; up to 1.9 mm. 

      Female:

• Body sausage-shaped to cylindrical. 
• Cuticle thick, lacking a typical lateral field (sometimes marked by irregularities in body annuli and/or superficial longitudinal lines extremely variable within the same species). 
• Body annuli either retrorse, provided or not with lobation, crenation, scales or spines, or rounded and covered or not with an extra-cuticular layer. 
• Labial area variously shaped; submedian lobes absent or variously developed.  Labial sclerotization strong. 
• Stylet massive; cone much longer than base plus knobs; stylet knobs anchor-shaped or sloping backwards. 
• Isthmus very short; esophageal glandular bulb markedly reduced.        

 Male:

• No stylet. 
• Spicules variously shaped. 
• Caudal alae absent or well-developed.   

 Juvenile:

• Cuticle showing same range of variations as in female, but in some groups, juvenile and female may have different ornamentation; cuticular spines or scales, if present, arranged in longitudinal rows, stylet non-reduced, functional (lacking in some male J4 of Hemicycliophora spp.).

A very large number of species has been described within the family, many of nwhich may be invalid. Geraert (2010) has provided an extremely useful framework for the family, including the partitioning of genera into five subfamilies of genera with similar morphometric and morphological characteristics.

 Etymology:

• From the Greek: krikos = ring, nema = thread

Biology and Ecology:

Nematode species in the Criconematidae feed ectoparasitically on plant roots, some at root tips, others in more mature regions of the root, including areas where the root surface is disrupted by lateral root emergence.  Long stylets allow penetration and feeding from cells several layers deep at the root tip or in the root cortex.

Common plant hosts for criconematids are grasses and woody perennials.  Population levels may be severely underestimated if extraction techniques are used that rely on nematode movement and activity.  Density-flotation extraction techniques are more efficient in recovery of these nematodes (Ferris, et al., 2004; Olson et al., 2017)..

Some criconematids have rather thick bodies and are fairly inactive or move rather sluggishly, others are encumbered by a loose extra cuticle layer which impedes their movement.  Their exposure on the root surface, and their relative immobility, must render them accessible to predaceous and parasitic organisms in the rhizosphere.  That exposure, however, is offset by the protection provided by the thick cuticle in some genera or the extra cuticular sheath in others.  Effects of predation are also offset by the partitioning of assimilated resources into production rather than movement.  Some very rapid increases in abundance have been documented for Mesocriconema xenoplax in Prunus sp., for example (Ferris, et al., 2004).

Despite the morphologically-based protective mechanisms, some criconematids are quite susceptible to parasitism by predaceous fungi, for example, Hirsutella rhossiliensis, and to egg mortality through the activity of flourescent pseudomonads (Jaffee et al., 1989; Kleupfel et al., 2002).

References:

Ferris, H., M.V. McKenry, B.A. Jaffee, C.E. Anderson, and A. Juurma. 2004. Population characteristics and dosage trajectory analysis for Mesocriconema xenoplax in California Prunus orchards.  Journal of Nematology 36:505-516.

Geraert, E. 2010. The Criconematidae of the World. Identification of the family Criconematidae (Nematoda). Academia Press, 615p.

Jaffee, B. A., J. T. Gaspard and H. Ferris.  1989.  Density-dependent parasitism of the soilborne nematode Criconemella xenoplax by the nematophagous fungus Hirsutella rhossiliensis.  Microbial Ecology 17:193-200.

Kluepfel, D.A., A.P. Nyczepir, J.E. Lawrence, W. Wechter, and B. Leverentz. 2002. Biological Control of the Phytoparasitic Nematode Mesocriconema xenoplaxon Peach Trees. J. Nematology 34:120-123.

Raski, D.J. and Luc, M. 1987. A reappraisal of Tylenchina (Nemata) 10. The superfamily Criconemaroidea Taylor, 1936. Rev. Nemarol. 10:409-444.

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