Description of Trithornus aquatica gen. n. sp. n. (Nemtoda:Cephalobina) from aquatic habitat, India.

Abstract: A new cephalobid nematode, Trithornus aquatica gen. n. sp. n. has been described and illustrated. The new genus can be distinguished by the unique shape of its labial probolae, consisting of swollen labial shaft and a trifurcated apical section. The cephalic probolae is triangular in shape. Cuticle is transversely annulated, lateral field with five incisors, outer ones being undulate. The stoma comprises of cheilostom with granular rhabdia, gymnostom narrower than cheilostom and stegostom. Stegostome can be differentiated into three parts meta, meso and telo. A tooth is present on mesostegostome. Females have cephaloboid type of reproductive system. Tail is elongate conoid with a pointed tip. Males were not found. The newly described genus closely resembles Acrobeles Linstow, 1877, Chiloplacus Thorne, 1937 and Cervidellus Thorne, 1937 in having similar stoma, furcated labial probolae, simple cuticle and cephaloboid type of female gonad with a post uterine sac. But, is clearly distinguishable by the related genera on the basis of the shape of labial probolae and the presence of outer undulated lateral lines. A dichotomous key to the identification of the genus has also been provided.