Metazoan parasites in Colomesus asellus (Pisces: Tetraodontidae) from Amazon River, in Brazil: an ecological, annual and seasonal study.

Our hypothesis is that annual and seasonal variations influence the structure of component communities and diversity of metazoan parasites from Colomesus asellus from the Amazon River. A total of 107 fish were collected during 2020 and 2021, and 932 metazoan parasites were recovered. In 2020, four species of parasites (one Nematoda, two Digenea and one Crustacea) were found; and in 2021, five species (one Nematoda, one Digenea, one Acanthocephala and two Crustacea) were recorded. Ergasilus colomesus was the most dominant throughout the study. Species richness and Brillouin diversity index were higher in 2021 and in the dry season. Some parasite component communities showed differences between years and between seasonal periods. The structure of parasite communities was mainly influenced by rainfall levels, seasonal availability of infective stages in the environment, and body size of the fish host. These facts corroborate the hypothesis that such variables could influence the component communities of parasites. Lastly, this is the first record of Contracaecum sp., Genarchella genarchella, Clinostomum marginatum, Brasacanthus sp. and Argulus pestifer in C. asellus