Description of Crassolabium unicum sp. n. (Nematoda: Dorylaimida: Qudsianematidae) from Vietnam

Crassolabium unicum sp. n., collected from a natural habitat in Vietnam, is described and illustrated. The new species is characterized by its 0.77-0.94 mm long body, three-layered cuticle, lip region offset by depression and 12-13.5 mu m broad, odontostyle 13.5-15 mu m long with wide aperture occupying 36-46% of its length, neck 235-260 mu m long, pharyngeal expansion 117-131 mu m long or occupying 47-52% of total neck length, anterior part of intestine presenting very distinct folds, female genital system didelphic-amphidelphic, uterus simple and 28-43 mu m or 0.7-0.9 body diameters, vulva transverse (V= 45-52), prerectum bearing a blind postrectal sac, caudal region short and rounded (21-25 mu m, c = 45-61, c '= 0.6-0.8) with two (dorsal and ventral) lacunae between outer and intermediate cuticle layers, and male unknown. It is compared with the similar representatives of the genus.