Influence of host sex and age on infracommunities of metazoan parasites of Prochilodus lineatus

149 specimens of Prochilodus lineatus were collected on the upper Paraná River floodplain. Of these, 121 (82.1 %) were parasitized. 33 species of metazoan parasites were recorded. Rhinonastes pseudocapsaloideum was classified as secondary, while all other species were classified as satellites. Ergasilus sp. and Tereancistrum curimba were positively associated and their abundances were positively correlated. Saccocoelioides magnorchis and S. nanii were positively associated and their abundances were positively correlated. The mean diversity in the infracommunities of P. lineatus was H = 0.6875 ± 0.4398. Host standard length was not correlated with parasite diversity (rs = 0.1726; p = 0.0533). The abundances of T. curimba and Kritskyia boegeri, and S. magnorchis and S. nanii were significantly correlated with host length. Correlation between fish age and parasite prevalence was not significant. The abundances of Amplexibranchius sp., K. boegeri and S. magnorchis were significantly different among host age classes. For Amplexibranchius sp., the three-year old age class had more parasites. For K. boegeri, the intermediate age classes had the most numerous parasites. Only Tereancistrum curimba showed significant difference in the prevalence between the sexes, with females being more parasitized

Influence of host sex and age on infracommunities of metazoan parasites of

149 specimens of Prochilodus lineatus were collected on the upper Paraná River floodplain. Of these, 121 (82.1 %) were parasitized. 33 species of metazoan parasites were recorded. Rhinonastes pseudocapsaloideum was classified as secondary, while all other species were classified as satellites. Ergasilus sp. and Tereancistrum curimba were positively associated and their abundances were positively correlated. Saccocoelioides magnorchis and S. nanii were positively associated and their abundances were positively correlated. The mean diversity in the infracommunities of P. lineatus was H = 0.6875 ± 0.4398. Host standard length was not correlated with parasite diversity (rs = 0.1726; p = 0.0533). The abundances of T. curimba and Kritskyia boegeri, and S. magnorchis and S. nanii were significantly correlated with host length. Correlation between fish age and parasite prevalence was not significant. The abundances of Amplexibranchius sp., K. boegeri and S. magnorchis were significantly different among host age classes. For Amplexibranchius sp., the three-year old age class had more parasites. For K. boegeri, the intermediate age classes had the most numerous parasites. Only Tereancistrum curimba showed significant difference in the prevalence between the sexes, with females being more parasitized

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli (Eoacanthocephala, Neoechinorhynchidae) of Pimelodus maculatus Lacépède (Siluroidei, Pimelodidae) of the São Francisco River, Brazil

Ecological and reproductive aspects of Neoechinorhynchus pimelodi Brasil-Sato & Pavanelli, 1998, in Pimelodus maculatus Lacépède, 1803 collected in the São Francisco river during periods of drought (July 1995 and 1996) and floodings (January 1996 and 1997) of this river basin are provided. In tropical regions where the amount of rainfall alters the hydrological regimen of limnological systems water temperature has not had an important role in infections of N. pimelodi in P. maculatus. Prevalence was somewhat higher during drought periods. Intensity of infection varied slightly between collecting periods. Mature male and female acanthocephalans were present in all periods. Females were predominant. Mature females were present in higher numbers during flooding periods with a corresponding decrease in juvenile acanthocephalans. Recruitment and constant losses of N. pimelodi seem to be controlled by transmission mechanisms independently of density. Mechanisms may consist of infected prey availability (potential intermediate hosts) and changes of preferred alimentary items in the diets of juvenile and mature P. maculatus