Relative condition factor and parasitism in anostomid fishes from the floodplain of the Upper Paraná River, Brazil.

Individuals of four species of Leporinus were captured in the floodplain of the Upper Paraná River and their metazoan parasites were collected. Fifty-eight taxa of ectoparasites and endoparasites were recorded: 31 in Leporinus lacustris, 32 in Leporinus friderici, 28 in Leporinus obtusidens and 25 in Leporinus elongatus. The aim of this paper was to study the relationship between the host's condition and the parameters of infrapopulations and infracommunities. The health of the host was represented by the relative condition factor (Kn). Richness and number of individuals in the infracommunities of ectoparasites covariated with the Kn of the hosts in one species of fish. Some infrapopulations of ectoparasites covariated negatively and/or the mean Kn of parasitized individuals was lower than those without parasites. The abundance in some infrapopulations of endoparasites covariated positively with the Kn and/or the mean Kn of parasitized fish was better. These results may be related to different transmission strategies used by ecto and endoparasites.