Ergasilus triangularis sp. n. (Copepoda, Poecilostomatoida, Ergasilidae) is proposed. The specimens were collected from gill filaments of the freshwater fishes Laemolyta taeniata from the rivers Jamari, Guaporé and Pacaás Novos , Rondônia State, Brazil. The new species has a falciform, pectinate spine on the exopodite of the first leg, that indicates relationship to seven previously described Amazonian species of Ergasilus.This species differs from others in size, shape of the antenna and armature of the legs.
Copepoda; Ergasilus; Amazon; new species