Occurrence of Intersexuality in "Lambaris", Astyanax scabripinnis (Jenyns, 1842), Small Characids from the

ABSTRACT During studies carried out with a small characid (Astyanax scabripinnis), from the Brazilian streams located in Cerrado biome, some gonads of fishes exhibited sparse oocytes in perinucleolar stage embedded in normally developing testicular tissues. Another pattern of gonad intersex with vitellogenic oocytes and mature lobules was observed in the gonads of fishes collected from a reservoir supplied by the Atlantic Forest stream. These gonads in different stages of maturation were examined histologically. The results revealed the patterns occurring in fishes of the same species, from four different populations. Key Words : Intersexuality, Neotropical ichthyofauna, Characidae, Tetras, Stream fishes * Author for correspondence INTRODUCTION Among the Characiformes, the freshwater fishes of the family Characidae and its subfamily Tetragonopterinae, the so-called South American tetras (Nelson, 1994), have the largest richness of species. This is a paraphyletic group predominating in the streams of several Brazilian hydrographic basins (Buckup, 1998). Among the Tetragonopterinae,