Nematodes of Astyanax fasciatus (Actinopterygii: Characidae) and their parasitic indices in the São Francisco river, Brazil.

The endoparasite fauna of Astyanax fasciatus from the upper São Francisco river was investigated and ecological parameters and morphological and morphometric data on the parasites are presented. A total of 74 specimens of banded astyanax were collected downstream from the Três Marias dam, municipality of Três Marias, Minas Gerais (18°12'32"S, 45°15'41"W) in January 2011 and January 2012. Eleven taxa of Nematoda were found: Contracaecum sp.; Hysterothylacium sp.; Goezia sp.; Brevimulticaecum sp.; Procamallanus sp.; Procamallanus (Spirocamallanus) saofranciscencis; Cystidicoloides sp.; Spinitectus rodolphiheringi; Rhabdochona sp.; Spiroxys sp.; and Eustrongylides sp.. The fauna of A. fasciatus consisted of by larval specimens of Contracaecum sp., Hysterothylacium sp., Brevimulticaecum sp., Cystidicoloides sp., and Spiroxys sp., and by adult specimens of P. saofranciscencis, whose prevalence was greater than 10%. Thus, this fish acts as an intermediate host of some species of larval nematodes especially, Anisakidae and Acanthocheilidae (Brevimulticaecum sp., new host record and new locality). It participates in transmitting species such Rhabdochona sp. to carnivorous fish and also acts as a definitive host for P. saofranciscencis and S. rodolphiheringi in the upper São Francisco river.