Abstract
This study compared the monogeneans community in C. monoculus from the Tapajós River (state of Pará) and Jari River (state of Amapá), northern Brazil. A total of 2188 monogeneans belonging to eight taxa were collected from the gills of fish: Gussevia arilla, Gussevia longihaptor, Gussevia tucunarense, Gussevia undulata, Sciadicleithrum ergensi, Sciadicleithrum umbilicum, Sciadicleithrum uncinatum and Tucunarella cichlae. Gussevia arilla was the dominant species for C. monoculus from the Tapajós River basin, while S. umbilicum predominated among the hosts from the Jari River basin. For the two populations of C. monoculus, the prevalence, mean intensity and mean abundance of monogeneans were different and the of parasites community had a high qualitative similarity (87.5 %). The monogeneans community of C. monoculus was characterized by high species richness, with infection values varying from low to moderate. The geographic distance and differences in environmental characteristics arising from the same did not influence the richness of species of monogeneans infesting C. monoculus in the Tapajós and Jari rivers, but appear to have been determinants in the differences observed in the structure of the monogenean communities in each region.