Ergasilus turucuyus sp. n. (Copepoda, Poecilostomatoida, Ergasiiidae) is proposed. The specimens were collected from the gill filaments of the freshwater fishes Acestrorhynchus falcatus and A. falcirostris from Pacaás Novos River, Rondônia state, Brazil. The new species has a falciform pectinate seta on the first exopod that indicates relationship to five previously described Amazonian species. This species differs from others in the ornamentation of the legs, antenna, abdominal somites and by having a wider cephalosome.
Copepoda; Ergasilus turucuyus; fish parasites; Amazon