Gamidactylus piranhus sp.nov. [Copepoda, Vaigamidae] from the nasal fossae of serrasalmid fishes from the Tres Marias Reservoir, Upper Sao Francisco River, Minas Gerais State, Brazil

Gamidactylus piranhus sp. nov. (Copepoda, Vaigamidae) from the nasal fossae of “San Francisco piranha”, Pygocentrus piraya (Cuvier, 1819) and.White piranha. Serrasalmus brandtii (Lütken, 1875) is described. The new species is similar to the type species of the genus, Gamidactylus jaraquensis Thatcher et Boeger, 1984, but differs from it in the following respects: the cephalothorax is shorter, the free thoracic segments are usually longer, leg 5 is reduced to a simple seta and a spine on the second antennal segment is lacking. Gamidactylus bryconis Varella, 1995 and Gamidactylus hoplius Varella et Malta, 1996, do not closely resemble the new species because they are much larger and both present leg 5 reduced to a double seta.