Gonadal Stage and Sex Steroid Correlations in Siberian Sturgeon, Acipenser baeri, Habituated to a Semitropical Environment

摘要

Stages of gonadal development, in association with plasma concentrations of the sex steroids 17 beta-estradiol (E2), progesterone (P4), testosterone (T), and 11-ketotestosterone (11-KT), were investigated for a single time point during a natural breeding season in 7-yr-old Siberian sturgeon, Acipenser baeri Brandt, exposed lifelong to a warmwater environment. Among females, examination of gonadal tissue showed variation in ovarian stage, with 12.5, 47.5, 22.5, and 17.5% of females found at Stages 2 (previtellogenic), 3 (early vitellogenic), 4 (mid-vitellogenic), and 5 (migratory nucleus), respectively. Although patterns varied among the hormones, plasma concentrations of E2, T, and 11-KT became increasingly elevated in females as maturation progressed. On the basis of histological criteria, males were classified as either premeiotic (quiescent) or meiotic and 50% of the males sampled were found at each stage. Significant elevations in circulating concentrations of plasma E2 and T were observed in meiotic versus premeiotic males, and there was a rise in plasma 11-KT concentration that approached significance (P = 0.056).