Profiles of gonadal development, sex steroids, aromatase activity, and gonadotropin II in the controlled sex change of protandrous black porgy, Acanthopagrus schlegeli Bleeker

The objectives of the present study were to investigate the effects of oral administration of estradiol-17 beta (E-2) on the sex steroids and gonadotropin II (GTH IT) in plasma, aromatase activity in gonad and brain, and sex change in protandrous black porgy, Acanthopagus schlegeli Bleeker. Two-year-old black porgy were divided into two groups, one fed a control diet and the other a diet mixed with E-2 (4.0 mg/kg feed) for 7 months. Significantly higher GSI was observed in the E-2 group. Fish treated with E-2 showed complete suppression of spermatogenesis and spermiation and induced sex change with vitellogenic oocytes and large primary oocytes. Lower levels of plasma 11-ketotestosterone and higher levels of plasma vitellogenin were shown in the E-2 group. Higher gonadal aromatase activity in concordance with elevated plasma levels of GTH II was observed in the E-2 group. The highest aromatase activity in the forebrain in the control group was observed in January. Higher aromatase activity in forebrain, midbrain, and hindbrain was also detected in the E-2 group than the control group. The change of aromatase activity in brain was more susceptible than that in gonad. The data showed that the increase of plasma GTH II levels and gonadal aromatase activity may be important to the controlled sex change by administration in black porgy. (C) 2000 Academic Press.