Serum levels of 17 beta -hydroxy-4-androstene-3,11-dione (11-KT) and testosterone in the protogynous black sea bass, Centropristis striatus fluctuate annually, correlated with the breeding season. Although serum 11-KT levels in both males and females exhibit seasonality, serum estradiol-17 beta concentrations cycle annually only in the females. Throughout the year, serum estradiol levels in males were significantly less than levels in breeding, or nonbreeding females. In all female sea bass not undergoing sexual succession, histological examination of the ovary revealed only spermatogonia restricted to the posterior male lamellae. In female fish undergoing sexual succession, ovarian tissue was always nonvitellogenic and regressing. Breeding females were not observed to undergo gender change. The possibility is discussed that sexual succession results from inhibition of ovarian tissue response to steroidogenic gonadotropin. |
