Community structure of metazoan parasites from Pimelodus blochii in two rivers of the Western Brazilian Amazon: same seasonal traits, but different anthropogenic impacts.

The present investigation evaluated the influence of seasonality and locality on the structure of the parasite community of the catfish Pimelodus blochii. A total of 160 fish were collected from two rivers in the State of Acre, western Brazilian Amazon: 80 fish in River Acre and 80 in River Iaco, with 40 in each season (rainy and drought). The overall prevalence was 78.7% and 1461 parasite specimens (adults and larvae) were allocated in 22 taxa: 5 of Monogenea, 10 of Nematoda, 3 of Digenea, 1 of Cestoda and 3 of Crustacea. In drought season, Procamallanus (Spirocamallanus) pimelodus and Demidospermus peruvianus were more prevalent in River Acre and Iaco, respectively. The parasite diversity (Brillouin index) as well as the prevalence and abundance of the monogeneans D. peruvianus, D. striatus, Demidospermus sp. and Ameloblastella sp. were higher in River Acre. The parasite community structure were dissimilar among rivers, and seasonally in River Iaco. These results suggest that environmental traits may overshadow seasonal influences on the parasite community structure, which may be related to the higher anthropization in River Acre. Furthermore, seasonality exerted less influence on the parasite community than expected, probably because the two rivers have different hydrological traits than those of other rivers in the Brazilian Amazon. New host and locality records expanded our knowledge of parasite biodiversity of P. blochii.