The reproductive cycle of Anodontites trapesialiswas studied from May 1998 to April 1999. Quantitative analysis of the sexual cycle revealed that the species is exclusively hermaphrodite with separate male and female follicles. Gametogenesis is continuous with peaks of maturation and elimination of gametes during dry season. The period of maximum maturation of the oogenesis was in April and May, when mature oocytes were observed filling the follicles and gonoducts. Spermatogenesis was recognized by a proliferation phase with developing cells with period of maturation since April to July. These cells started to differentiate giving origin to spermatic morulae and free spermatozoa organizing the radial spermatic series. During the period of discharge of the gamets, the majority of follicles presented aggregates of spermatozoa forming the spermballs, which characterize the species as spermatozeugmata.
Bivalvia; hermaphroditism; Pantanal; sperm morulae; spermatozeugmata
