Gastrointestinal nematodes of freshwater fish from Pilcomayo River, Argentina, including description of a new species of Procamallanus (Spirocamallanus).

Helminthological examination of viscera of six freshwater fish species, collected from Misión la Paz, Pilcomayo River, Province of Salta, Argentina, revealed the presence of five species of parasitic nematodes belonging to the Camallanidae, Cystidicolidae, Cucullanidae and Anisakidae  The material also contained one unknown species, Procamallanus (Spirocamallanus) tomsici sp. nov. collected from Pimelodus albicans, Pygocentrus nattereri and Hoplias misionera. This species is distinguished from its congeners all over de world by possessing six pores distinctly surrounding the mouth aperture, a buccal capsule with 3-4 spiral thickenings complete, females possessing a lateral cuticular ornamentation along the body, and two pairs of preanal and three pairs of postanal papillae in males. The findings represent new hosts and geographical records.