Avaliação da fauna parasitária de Prochilodus argenteus Spix & Agassiz, curimatã-pacu (Actynopterygii: Prochilodontidae) do Alto São Francisco, Minas Gerais, Brasil

Abstract

Specimens of Prochilodus argenteus (Actynopterygii: Prochilodontidae) were collected in the upper São Francisco River, downstream from the Três Marias Dam and downstream of the confluence of the Abaeté River with the San Francisco between 2004 and 2008 during periods of dry and rain. We found 34 species of parasites: adult specimens of Saccocoelioides nanii; Anacanthoroides sp. Apedunculata discoidea; Telethecium sp; Tereancistrum ornatus; Tereancistrum toksonum; Tereancistrum sp.1, sp.2, sp.3 and sp4.; Rhinonastes sp.; Guyanema sp.; Philometra sp.; Philometrioides sp.; Spinitectus asperus; Neoechinorhynchus prochilodorum; Acusicola sp.; Argulus multicolor; Dolops nana; Gamidactylus sp. Placobdella and unidentified copepod sp. and larval specimens of Henneguya sp. Myxobolus franciscoi; Myxobolus sp.1 sp.2; Acanthostomum sp.; Austrodiplostomum sp.; metacestode sp.2 and sp.1; Valipora sp.; Contracaecum sp.; Hysterothylacium sp. and Lernaea sp.. Associations were found between different pairs of species, thus were inferred that the presence of a species favored the presence and increased abundance of others. Among the biotic factors, sex of the hosts did not influence the prevalence, intensity and abundance indexes of ecological infrapopulations or diversity, dominance and evenness, ecological indexes infracommunity. The standard length and body weight showed a weak negative correlation with some indices and ecological communities of hosts smaller and lighter were characterized by greater richness and lower dominance. The relative condition factor and the coefficient of growth when compared with the default values of the collection site showed no changes in infected individuals collected downstream of the dam of Three Marias, but these proved to be decreased in infected fish collected downstream from the confluence of the river San Francisco with the Abaeté River. Hosts from the two locations and collection periods showed different parasitological indexes, and those collected downstream from the Três Marias dam during the dry period were most affected by this phenomenon. It is likely that these differences are linked to differences in the dist composition in different locations and collection periods. Limnological conditions different between the two sites and then modulate the reproduction of P. argenteus and may be relevant factors in determining patterns of parasitism. Additional studies about migration conducted by the populations of P. argenteus are necessary to better understand the parasitism and its variations in this region.