Infections by helminth parasites in "Puyenes", Galaxias maculatus (Galaxiidae, Salmoniformes), from southern Argentina with special reference to Tylodelphys barilochensis (Digenea, Platyhelminthes)

The occurrence of Tylodelphys barilochensis, Acanthostomoides apophalliform is, Contracaecum sp. and Camallanus corderoi infecting Galaxias maculatus ( "puyenes") was quantified for the first time in Lake Nahuel Huapi, southern Argentina. T. barilochensis was recorded in this lake for the first time. The role of G. maculatus population in transmission of parasites to the sal monids is more important for Contracaecum sp. (prevalence 14-34%) and A. ap ophalliformis (prevalence 30-54%) than for C. corderoi (prevalence 6-8%). T he absence of Diphyllobothrium spp. in samples shows that the G. maculatus population does not play any role in the life cycles of these important zoo notic parasites. The sex of the host had no effect on T. barilochensis abun dance. Statistical differences in T. barilochensis abundance between "puyen es" of the same size class between sampling stations and positive correlati on between prevalence of infected snails and T. barilochensis abundance in fish suggest that different stocks have been sampled. Factors influencing T . barilochensis abundance are discussed.