Brachyplatystoma vaillantii is a large migratory catfish widely distributed in the Amazon basin, but its parasitic fauna is still poorly known. As it is an important fishery resource in the region of the Amazonas River estuary, the aim of this study was to investigate the parasite community in B. vaillantii from a tributary of the Amazonas River estuary system, in Brazil. We examined 31 juvenile fish, of which 80.6% were parasitized, and a total of 586 parasites were collected. We identified Dermidospermus brachyplastystimae and Dermidospermus araguiensis (Monogenea), Genarchella genarchella (Digenea), Harriscolex piramutab (Cestoda), Pseudoterranova sp. (Nematoda), Ergasilus xinguensis (Crustacea) and mites (Acarina). The dominance was of Pseudoterranova sp. larvae. The parasite community of B. vaillantii was composed of low values of species richness (2.0 ± 1.4), evenness (0.18 ± 0.21) and diversity (0.32 ± 0.37), with predominance of ectoparasite species with low prevalence, low abundance and overdispersion. Host body weight was the main correlate of parasite diversity and abundance, and a diet rich in crustaceans and other invertebrates may be important in structuring the parasite community of B. vaillantii. This is the first report of Dermidospermus brachyplastystimae and D. araguiensis, Pseudoterranova sp. and G. genarchella for B. vaillantii.

The aim of this study was to investigate the ecology and diversity of community and infracommunities of metazoan parasites Geophagus altifrons (Heckel, 1840) in Rio Jari, in the state of Amapá, in the eastern Amazon region. From the total of 31 fish examined, 90.3% were parasitized by one or more species, collecting a total number of 806 parasites. The parasites species identified were: Sciadicleithrum geophagi, Posthodiplostomum sp., Procamallanus (Spirocamallanus) inopinatus, Raphidascaris (Sprentacaris) sp., Genarchella genarchella, Gorytocephalus spectabilis and Ergasilus xinguensis. Most of the parasites showed an aggregate dispersion pattern. Brillouin diversity index, uniformity and species richness of parasites were low. The component community of parasites was constituted by ectoparasites and endoparasites, but with a predominance of ectoparasites. The body size of hosts had a low effect on the parasites infracommunities. This first eco-epidemiological study for G. altifrons reports these parasites in a host, for the first time, with the exception of S. geophagi and E. xinguensis.