Reproduction of the lambari Astyanax scabripinnis (Jenyns, 1842) (Pisces: Characidae) in a small stream in Southeastern Brazil

摘要

The reproduction of Astyanax scabripinnis captured bimonthly in the Cristais small stream (20o00'03'S and 43o56'46'W), in the Das Velhas River basin, was studied using gross anatomical and histological techniques. Standard length of females (56 pl 8 mm) was longer than males (49 pl 6 mm). The diameter of the nucleus of the primary spermatogonia was 7.5 pl 0.9 om and of the spermatozoon head 1.8 pl 0.4 om. For the females, the oogonia nuclei measured 10.2 pl 2.2 om and the vitellogenic oocyte nuclei measured 675.0 pl 66.7 om. The following stages of the reproductive cycle were established: developing, mature, partially spent/spawned and completely spent/spawned. Maximum number of males (61.3%) and females (58.2%) at the mature stage was observed during November/December. The gonadosomatic index of males and females was highest during the mature stage (2.4 pl 0.6; 7.5 pl 1.3, respectively) and decreased in subsequent stages. In females, the hepatosomatic index was highest during the developing stage (2.8 pl 0.3), and slightly decreased in the following stages. The highest stomach repletion index found for males was observed during the partially spent stage (2.0 pl 1.2), while for the females, this index varied discretely between the reproductive stages. The highest values of Fulton's condition factor were registered during the mature stage in both sexes (2.9 pl 0.4 for males; 3.0 pl 0.3 for females). The continuous reproductive period and the presence of partially spawned females during the entire sampling period indicated that the species has fractional spawning.