Three new species of oxyuroid nematodes,including two new genera,from freshwater catfishes in Brazil

Three new oxyuroid nematode species of the family Pharyngodonidae are described from the intestine of freshwater catfishes in Brazil (River Paraná), two of them being representatives of new monotypic genera: Ichthyouris brasiliensis n. sp. from Pterygoplichthys aculeatus, Brasilnema pimelodellae n. g., n. sp. from Pimelodella gracilis, and Parasynodontisia petterae n. g., n. sp. from Rhinelepis aspera. I. brasiliensis n. sp. differs from the only other congeneric species, I. ro, mainly in the absence of a pair of plate-like structures in the male caudal region, shorter caudal alae, the presence of a pair of conspicuous lateral spines at the level of the anal opening in the female and by other features. Brasilnema n. g. is characterised mainly by a hexagonal oral opening, a broad buccal capsule containing three teeth, a simple spicule and an amphidelphic uterus, whereas Parasynodontisia n. g. is characterised by a triangular oral opening and an amphidelphic uterus in the female; both genera possess six small, triangular, circumoral lamellae slightly raised above the apical surface. The paper includes a key to the pharyngodonid genera whose species are parasitic in fishes.