Criconematoidea (Taylor, 1936)
Criconematina (Siddiqi, 1980)
Hemicycliophoroidea (Skarbilovich, 1959)
Tylenchocriconematoidea (Raski & Siddiqui, 1975)
Characteristics Chart of the Order Tylenchida
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 spheroidal.
- 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.
- 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 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;
either slender and offset from glandular bulb or short, broad and amalgamated
with glandular bulb.
- Esophageal glandular bulb 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 Ám) 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
- Swollen female may deposit numerous eggs in a gelatinous matrix produced by the
- Intestine syncytial, lacking a definite lumen, often
extending beyond anus.
- Female anus a small pore, absent in rare cases.
- 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.
Raski & Luc, Rev. Nematol. 10(4):409-444 (1987)