Criconematoidea

Female Criconema, photographed by Tom Powers.

Belongs within: Tylenchina.

The Criconematoidea are a group of soil-dwelling nematodes in which the females are parasites of plant roots, while the free-living males do not feed as adults.

Characters (from Raski & Luc 1987): All stages usually under 1 mm long, rarely up to 1.9 mm (Hemicycliophoridae). Marked sexual dimorphism: male slender, female sausage-shaped, cylindrical or sphaeroidal.
Female and juvenile with very variable cuticle: thick with retrorse annuli lacking lateral field, provided or not with lobation, 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. Amphidial apertures round to oval, close to labial disc area. 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. Deirids reported in thin-cuticled genera Tylenchulus and Paratylenchus. 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 oesophagus 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 either slender and offset from glandular bulb or short and broad being amalgamated with glandular bulb. Oesophageal glandular bulb small, usually offset from intestine. Orifice of dorsal oesophageal 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: one branch, anterior, outstretched (may be coiled in swollen females). Post-vulval uterine sac absent. In juveniles: Female genital primordium showing 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 ovijector can have a thickened wall, rarely transformed into a cyst. Swollen female may deposit numerous eggs in a gelatinous matrix produced by the excretory system. Intestine syncytial, lacking a definite lumen, often extendmg beyond anal level. Female anus a small pore, rarely absent.
Male : Small, slender. Cuticle thin, with narrow annuli; no extra cuticular layer; typical lateral field present. Stylet mostly absent, or degenerated and nonfunctional. Oesophagus 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 sometimes well-developed, leptoderan. Cloacal lips usually narrow and elevated, or drawn out as a penial tube. Hypotygma present or absent.

<==Criconematoidea
    |--Hemicycliophora de Man 1921 E86 [Hemicycliophoridae LB02]
    |    |--H. arenaria L02
    |    `--H. mikoletzkyi Goffart 1950 [=Procriconema mikoletzkyi Goffart 1949 (n. n.)] E86
    |--Tylenchulidae LB02
    |    |--Tylenchulinae W02
    |    |    |--Tylenchulus semipenetrans W02
    |    |    `--Trophotylenchulus obscurus W02
    |    `--Paratylenchus [Paratylenchinae] W02
    |         |--P. dianthus W02
    |         `--P. projectus W02
    `--Criconematidae LB02
         |--Hemicriconemoides chitwoodi H02
         |--Criconemella [Criconematinae] W02
         |    `--C. xenoplax W02
         |--Criconemoides Taylor 1936 E86
         |    `--C. stygia (Schneider 1940) [=Criconema stygia] E86
         `--Criconema Hofmänner & Menzel 1914 [incl. Iota Cobb 1913] E86
              |--C. minor (Schneider 1940) [=Iota minor] E86
              |--C. paxi (Schneider 1940) [=Iota paxi] E86
              `--C. southerni (Schneider 1940) [=Iota southerni] E86

*Type species of generic name indicated

REFERENCES

[E86] Eder, R. 1986. Nematoda from continental subterranean aquatic habitats. In Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) (L. Botosaneanu, ed.) pp. 125-132. E. J. Brill / Dr. W. Backhuys: Leiden.

[H02] Hope, I. A. 2002. Embryology, developmental biology and the genome. In The Biology of Nematodes (D. L. Lee, ed.) pp. 121-145. Taylor & Francis: Florence (Kentucky).

[L02] Lee, D. L. 2002. Cuticle, moulting and exsheathment. In The Biology of Nematodes (D. L. Lee, ed.) pp. 171-209. Taylor & Francis: Florence (Kentucky).

[LB02] Ley, P. de, & M. Blaxter. 2002. Systematic position and phylogeny. In The Biology of Nematodes (D. L. Lee, ed.) pp. 1-30. Taylor & Francis: Florence (Kentucky).

Raski, D. J., & M. Luc. 1987. A reappraisal of Tylenchina (Nemata): 10. The superfamily Criconematoidea Taylor, 1936. Revue de Nématologie 10 (4): 409-444.

[W02] Wyss, U. 2002. Feeding behaviour of plant-parasitic nematodes. In The Biology of Nematodes (D. L. Lee, ed.) pp. 233-259. Taylor & Francis: Florence (Kentucky).