PLASMA TESTOSTERONE AND 11-KETOTESTOSTERONE LEVELS OF MALE PACU PIARACTUS-MESOPOTAMICUS (CYPRINIFORMES, CHARACIDAE)

The levels of testosterone (T) and 11-ketotestosterone (11-KT) of the South American pacu Piaractus mesopotamicus were determined by radioim munoassay during two stages of the reproductive cycle, i.e., resting a nd maturation, and the gonadosomatic index (GSI) was calculated. The h ighest levels of T and 11-KT were reached during the maturation stage (T = 2400 +/- 56 pg/ml; 11-KT = 2300 +/- 60 pg/ml) and lower levels we re maintained during the resting period. The rise in androgen levels o ccurred with the appearance of spermatozoa in the maturation stage, wh en GSI was highest.