Brasergasilus bifurcatus sp. nov. (Copepoda, Ergasilidae, Abergasilinae) from the gills and nasal fossae of serrasalmid fishes from the Três Marias Reservoir, Upper São Francisco River, Minas Gerais State, Brazil

Abstract Brasergasilus bifurcatus sp. nov. (Copepoda, Ergasilidae, Abergasilinae) is described. Specimens of the new species were collected from the gills and nasal fossae of the serrasalmid fishes, known as “piranhas”, Pygocentrus piraya (Cuvier, 1819) and “pirambebas”, Serrasalmus brandtii (Lütken, 1875). The fishes were netted in the Três Marias Reservoir (18°12′59″S, 45°17′34″W) of the upper São Francisco River, Minas Gerais State, Brazil. The new species differs from its congeners by the following characters: the specific setation on the antennule; the terminal barb of the antenna; the deeply bifurcate distal segment of the mandible; the chalice-shaped genital complex; a conspicuous external indentation of the second segment of the first endopod and a very short terminal segment of the first exopod.