The aim of the present study was to provide a current survey of the species of parasites found in the Upper Paraná River floodplain, as well as to investigate which strategies and mechanisms used by parasites, are favored and which environmental factors influence the parasite community in the studied environments. During a seven-year period from February 2000 to September 2007, 3,768 fish belonging to 72 species were collected and analyzed for the purpose of studying the parasite fauna. A total of 337 species of parasites were reported, including 12 new descriptions: one myxosporid, Henneguya paranaensis Eiras, Pavanelli and Takemoto Keywords: ichthyoparasites, biodiversity, helminthes, crustaceans, parasite ecology. Diversidade dos parasitos de peixes da planície de inundação do Alto Rio Paraná, BrasilResumo O objetivo do presente trabalho foi realizar um novo levantamento das espécies de parasitos encontradas na planície de inundação do Alto Rio Paraná, bem como investigar quais estratégias e mecanismos utilizados pelos parasitos são mais favorecidos e quais fatores ambientais estão influenciando a comunidade parasitária nos ambientes estudados.

Despite the magnitude of domestic and industrial pollution, fishery yield registered in several landing points at

We examined 44 specimens of Metynnis lippincottianus (Cope, 1870) (Characidae), collected in the Upper Paraná River floodplain, Brazil, from March 2006 to December 2007. Of the total number of fishes, 32 (72.7 %) were infected by at least one species of helminth (endoparasites). One digenean, Dadayus pacupeva, and four nematode species, Spinoxyuris oxydoras, Contracaecum sp. (larval stage), Procamallanus (Spirocamallanus) inopinatus and Raphidascaris (Sprentascaris) mahnerti were identified. D. pacupeva and S. oxydoras showed the highest values of prevalence, mean intensity and abundance. The typical pattern of overdispersion or aggregation was observed for all endoparasites. Dominance by D. pacupeva and S. oxydoras was observed in the parasite community. Positive association between D. pacupeva and two nematode species (S. oxydoras and P.(S.) inopinatus) was observed, including positive and significant covariation between their abundances. These results suggest that species are coexisting without competition. There was no correlation between parasitism and sex for M. lippincottianus.

SummaryIn order to examine the ecological relationships of metazoan parasites and their hosts, 63 specimens of Steindachnerina brevipinna have been collected from April to September 2006, in the rivers Guairacá and Corvo, tributaries of the low Paranapanema River. Five different parasite species have been found (Paranaella sp., Sphicterodiplostomum musculosum, Cosmoxynema vianai, Travnema travnema and Spinoxyuris sp.), with parasite richness from 1 to 4. The dominance index (C > 0.25) was calculated for S. musculosum and aggregation of S. musculosum and Paranaella sp. were reported. There were no associations or covariations between the species of parasites. Values did not show interference of parasite abundance at different gonadal maturity stages. The relative condition factor (Kn) did not show significant values regarding quantitative and qualitative data on parasitism. Statistical tests were significant between the prevalence and the abundance of parasites and the standard length of the hosts, as well as for the parasite abundance in different months and tributaries.

Paranaella luquei is a monogenean from family Microcotylidae, which was found parasitizing the gills of Steindachnerina brevipinna (Eigenmann & Eigenmann, 1889), collected in two different tributaries of Paranapanema River, Paraná, Brazil. This parasite was the first species of Microcotylidae described parasitizing freshwater fishes (Hypostomus sp., Hypostomus regani (Ihering) and Rhinelepis aspera Spix & Agassiz (Loricariidae) in the country.