Parasites of 136 specimens of Hemisorubim platyrhynchos, popularly called jurupoca, were analyzed. Fourteen parasite species were recorded: four digeneans (Crocodilicola pseudostoma, one Gorgoderidae species, Sanguinicola platyrhynchi, and Sphincterodiplostomum sp.); three cestodes (Goezeella paranaensis, Spatulifer maringaensis, and Mariauxiella piscatorum); five nematodes (Contracaecum Type 1 larvae of Moravec, Kohn, & Fernandes, 1993; Contracaecum Type 2 larvae of Moravec, Kohn, & Fernandes, 1993; Cucullanus (Cucullanus) zungaro; Eustrongylides ignotus; and Goezia sp.); one acanthocephalan (Quadrigyrus machadoi), and one pentastomid (Sebekia sp.). Most of the helminth specimens were found in larval stages, confirming that H. platyrhynchos is a significant source of their transmission. No dominance was reported. With the exception of Contracaecum Type 2 (featuring random dispersion), the species had a clumped pattern of dispersion in the host sample. Evidence of competition among parasite species was not reported. Several species of parasites were correlated with host size and sex. This fact may be explained by increase in food content and possible behavioral modifications of male and female hosts. Infracommunity diversity was not related to host size or sex.

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.

RESUMO. Foram investigadas as faunas parasitárias deLeporinus lacustris e Leporinus friderici da planície de inundação do Alto rio Paraná, Brasil, objetivando compará-las em composição e estrutura das comunidades seguindo-se metodologias usuais no estudo dos parasitas. Foram observados alguns padrões e as faunas podem ser consideradas semelhantes em estrutura. A principal diferença nas faunas parasitárias refere-se às taxas diferenciais de utilização das espécies hospedeiras por algumas espécies parasitas em comum, representadas pela abundância. Esse indicador diferiu entre as espécies de peixes mostrando que, apesar delas serem hospedeiras apropriadas, sua exploração ocorre de forma distinta.Palavras-chave: metazoários parasitas, Leporinus, planície de inundação, Alto rio Paraná.ABSTRACT. Parasite fauna of Leporinus lacustris and Leporinus friderici (Characiformes, Anostomidae) from the upper Paraná river floodplain, Brazil. The parasite fauna of Leporinus lacustris and Leporinus friderici from the Upper Paraná River floodplain, Brazil, was investigated aiming to make a comparison in terms of composition and structure of the communities. Usual methodologies in the study of parasite fauna were applied. Some patterns were observed, and the faunas can be considered similar in structure. The main difference in the parasite fauna was the use rate of the host by some shared parasite species, represented by abundance. This indicator differed in the fish species showing that, although all are appropriate hosts, their exploitation occurs in different ways.

ABSTRACT.Composition and structure of the endoparasite infracommunities of Gymnotus spp. (Pisces: Gymnotidae) of the Baía River, Mato Grosso do Sul, Brazil. Parasites of 111 specimens of the Gymnotus genus were analyzed. The fishes were captured in bolters and gill nets. Sixteen parasite species were recorded, being 93.7% of the species found in larval stages. Significant positive association and correlation between abundances of twenty pairs of species occurred. All the analyzed parasite species had a clumped pattern in host sample. No dominance was reported among the parasite species. Diversity of the infracommunities of male and female hosts were not different, but influence of hosts' sex in the prevalence and abundance of Tylodelphys sp. and Spiroxys sp. were observed. Significant positive correlation between hosts' total length and prevalence and abundance of Nomimoscolex chubbi, Contracaecum sp. 2 and Quadrigyrus machadoi was observed. The reproductive cycle of hosts was correlated with the Herpetodiplostomum sp. 1, Herpetodiplostomum sp. 3, Neodiplostomum sp. and Tylodelphys sp. prevalences.

No abstract

Fifty-one specimens of Acestrorhynchus lacustris (Lütken, 1875) collected on the Upper Paraná River floodplain were analyzed from February 2000 to November 2001. Of these, 35 (68.6%) were parasitized by at least one species of endohelminth. Eight species of endoparasites were found: five nematodes (Contracaecum Type 1 larvae of Moravec, Kohn and Fernades, 1993, Contracaecum Type 2 larvae of Moravec, Kohn and Fernades, 1993, Contracaecum sp., Eustrongylides sp. and Procamallanus sp.), two digeneans (Clinostomum sp. and Rhipidocotyle gibsoni Kohn and Fernandes, 1994) and one acanthocephalan (Quadrigyrus torquatus Van Cleave, 1920). Contracaecum sp. and Q. torquatus were positively associated and also had positively correlated abundances. There was significant difference in the prevalence and abudance of infection of Q. torquatus between hosts sexes. This parasite also presented negative correlation between its intensity and host standard length. There are significant positive correlation between the prevalence of Contracaecum Type 1 and host standard length.

A new species is of the genus Sanguinicola Plehn, 1905 described, Sanguinicola platyrhynchi n. sp., digenetic parasite of visceral cavity of Hemisorubim platyrhynchos (Valenciennes, 1840) from the floodplain of the upper Paraná River, Brazil. The species has been thus included because of the presence of separate dorsal genital pores, while differing from other species of the same genus mainly in digestive apparatus features, genital pore position, and infection site. Emendation of generic diagnosis is included.

No abstract