Morphology, Taxonomy and Morphometry of Some Cephalobidae (Nematoda: Rhabditida) From Brazil, With Descriptions of Two New Genera and Four New Species

Abstract

Sixty-three soil samples from Brazil yielded at least 19 species of Cephalobidae, including two new genera which are described. Cephalonema longicauda n. gen. n. sp. is characterized by an offset, button-like head, lips amalgamated, cheilorhabdions large, strongly sclerotized, vulva at mid-body and long tail. Heterocephalobellus brasiliensis n. gen. n. sp. is characterized by a very long oesophagus with loop, a very long post-vulval uterine sac and the same tail in both sexes. Heterocephalobus tabacum n. sp. is characterized by the posterior position of the excretory pore and by protruding papillae on the lips and Cephalobus pseudoparvus n. sp. by a long tail and rectum, anterior position of excretory pore and nerve ring and by distribution of the genital papillae in the male. Three synonyms are proposed: Acrobeles capensis as a junior synonym of A. mariannae, the genus Pseudocephalobus as a synonym of Teratolobus and the family Alirhabditidae as a synonym of the Cephalobidae. Species found for the first time since they were described are: Alirhabditis indica; Teratolobus regulus; Heterocephalobus pauciannulatus; Cephalobus pinguimucronatus; Acrobeles mariannae; Acrobeles singulus; Zeldia tridentata; Zeldia neocuta. Female T. regulus and a male A. mariannae are described for the first time. A study of morphometry showed that the extent of the papillar region in males is correlated with body length. In male and female the position of the excretory pore is correlated with oesophageal length but may not be calculated as a percentage because most of the regression lines do not pass through the origin. In all the species investigated, variability of the head region, female reproductive system and tail shape have been studied.