Nematode of the Week

Hexatylus nudus

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Hexatylus nudus (Thorne & Malek, 1968) n. comb.
Syn. Neotylenchus nudus Thorne & Malek, 1968


Hexatylus are different from most Tylenchid nematodes in that they have an entomoparasitic generation. This nematode was recovered from from a pasture located next to a corn field located in Howard County, Nebraska (41N 09’ 43’’ 98W 36’ 33”). The pasture has not been plowed for at least 40 years and is grazed annually by cattle. 

Allen Szalanski


Descriptions
    Order Tylenchida
    Suborder Hexatylina Siddiqi, 1980
    Superfamily Neotylenchoidea Thorne, 1941 (Jairajpuri & Siddiqi, 1969)
    Family Neotylenchidae Thorne, 1941
    Subfamily Neotylenchinae Thorne, 1941
    Genus Hexatylus Goodey, 1926 syn. Neotylenchus Steiner, 1931

    Thorne & Malek 1968, Siddiqi 1985
    Genus Neotylenchus Steiner, 1933
    Diagnosis: Neotylenchidae: Cephalic framework in 8 sectors of which the lateral may be greatly reduced. Median esophageal bulb absent. Esophagus joined to intestine by an obscure valvular apparatus. Spear knobs usually small. Ovary single, outstretched or reflexed. No posterior uterine branch. Bursa enveloping tail. 
    Entomoparasitic generation: Males and preadult, insect-parasitic females occasionally appear in fungus culture. Preadult infective females resembles those of Deladenus and most Sphaerularoididea, with much larger stylet bearing basal knobs and having enlarged oesophagel glands, exteremely elongated uterus filled with minute sperm and immature ovary. Preadult female supposedly penetrates an insect host and matures in its haemocoel.

    Thorne & Malek 1968
    Neotylenchus nudus n. sp.
    l 1.0 mm, a = 21; b = 9.1; c = 23; V = 81 93

    Body fusiform, excessively dense, obscuring many important detals of anatomy. Lateral fields marked by 4 incisures, difficult to observe, central band distinctly wider than the lateral. Lip region about 1/5 as wide as neck base. Spear 8u-10u long, apparently with minute knobs but these are difficult to observe. Esophageal corpus with a elongate-fusiform swelling containing outlets of submedian glands. Basla bulb variable in size, usually with only 2 nuclei visible. Cardiac attachment also obscure but probably a minute, muscular valve. Excretory pore and hemizonid as illustrated. Ovary extending forward to near esophagus base, usually with 1 or 2 fixtures, the oocytes in single file. Spermatheca packed with sperms. Tail conoid to small, rounded, mucronate terminus. Males not collected.
    Neotylenchus nudus is distinctive because of the almost pointed neck region, minutely knobbed spear, massive lobe of esophagus base, tail length compared to vulva-anus distance and mucronate terminus. 
    Holotype female and other specimens indexed under Neotylenchus 1.
    Habitat: Numerous specimens from prairie sod east of Towner, ND, and cultivated fields near Huron, SD, and Breckenridge, MN.
     

  • References:
    • Thorne, G. 1968. Nematodes of the Northern Great Plains. Part I Tylenchida (Nemata: Secernentea). South Dakota State University Technical Bulletin 31.
    • Siddiqi, M.R. 1985. Tylenchida parasites of plants and insects. CAB: UK.