Morphology and taxonomy of Rhabdias spp. (Nematoda: Rhabdiasidae) from reptiles and amphibians of southern Ontario

Rhabdias americanus n.sp., Rhabdias ranae Walton, 1929, Rhabdias fuscovenosa (Railliet, 1899), and Rhabdias eustreptos (MacCallum, 1921) from amphibians and reptiles of southern Ontario are described. Rhabdias americanus n.sp. and R. ranae have two large lateral pseudolabia beside the oral opening whereas R. fuscovenosa and R. eustreptos each have six lips arranged in lateral groups of three. Rhabdias americanus n.sp. is distinguished from R. ranae by the shape of the pseudolabia and by the presence of a cuticular ring on the posterior border of the buccal cavity which is absent in the buccal cavity of R. ranae. Rhabdias fuscovenosa is distinguished from R. eustreptos by its significantly smaller size and by the shape of the posterior quarter of the body which is straight in R. fuscovenosa and corkscrew shaped in R. eustreptos. Rhabdias fuscovenosa is the only species examined in which eggs in the uteri of gravid hermaphrodites were always at an early cleavage stage of development. In other species examined most eggs in the uteri contained first-stage larvae.