This study presents the helminthofauna of digenean parasites of Acestrorhynchus falcirostris in the state of Amazonas (Brazil). Eight species belonging to four families were recovered: Metacercariae of Austrodiplostomum compactum (Diplostomidae) and Clinostomum marginatum (Clinostomidae) and mature specimens of Bellumcorpus majus, Prosorhynchoides carvajali, Rhipidocotyle santanaensis (Bucephalidae); Prosthenhystera obesa (Callodistomidae); Genarchella genarchella (Derogenidae) and Phyllodistomum spatula (Gorgoderidae). Examining specimens belonging to the genus Bellumcorpus collected from A. falcirostris, were observed a great variation in the size and shape of testes, which also could be observed in the type specimens of Bellumcorpus majus and B. schubarti. Considering the similar morphology and morphometric characteristics of both species, in this paper B. schubarti is considered synonym of B. majus. Acestrorhynchus falcirostris is a new host records for all these species of digenean, except to A. compactum and C. marginatum. Prosorhynchoides carvajali is referred for the first time in Brazil.

This study exhibits data pertaining to the zoonotic potential of larvae of nematode of peacock bass (Cichla monoculus). Thirty-eight specimens were collected from Central Amazon floodplain lakes throughout the four seasons of a complete hydrological cycle: rising, high, receding and low water level. Third-stage larvae (L3) of Anisakis sp. and Contracaecum sp. Nematode larvae were found at prevalences of 13.15% and 7.89% respectively. The results indicated there being low infection hazard to humans consuming C. monoculus from floodplain lakes in Central Amazon.