OVARIAN DEVELOPMENT OF Oligosarcus hepsetus IN A BRAZILIAN RESERVOIR 169 HYSTOLOGICAL ANALYSIS OF OVARIAN DEVELOPMENT OF THE CHARACIFORM Oligosarcus hepsetus (CUVIER,

(With 3 figures) A histological analysis was performed of the ovarian development of Oligosarcus hepsetus (Cuvier, 1829), a medium-sized carnivorous Characiform species in the Lajes reservoir, Brazil. A total of 125 fishes, collected monthly between April 2001 and June 2002 were examined by routine macroscopic and his-tological techniques. Eight phases of the oocyte development were described, and 4 stages and 4 sub-stages of gonadal development were proposed. Spawning in reservoirs, similarly to that in rivers, is in batches, which favors juvenile survival and suggests that the impoundment of this area did not influ-ence the reproductive strategy of this very successful species in a dammed environment