Gonadal Development and Sex Steroid Hormone Levels of the Yellowfin Goby Acahthogobius flavimanus

摘要

Changes of sex steroid hormones in the plasma of yellowfm goby, Acanthogobius flavimanus were investigated in relation to the gonadosomatic index (GSI), the hepatosomatic index (HSI) and gonadal development. The GSI in females rose rapidly in Novemberand remained high from December to May (7.26+-0.89-6.62+-0.02). The Male's GSI also increased gradually from November and was highest in May (0.16+-0.08). The HSI in both sexes was in reverse correlation with the GSI, and the HSI was low during the spawning season (February-May). In females, the estradiol-17 beta (E_2) level increased during vitellogenesis (November and December) and reached its maximum (8.13+-2.87 ng/mL) at the maturing period, in January. 17 alpha 20 beta-dihydroxy-4-pregnen-3-one (17 alpha 20 beta OHP) gradually increased from October (0.063+-0.02 ng/mL) to March (0.16+-0.02 ng/mL) and increased rapidly in May. The level of testosterone (T) showed a similar tendency of E_2. In males, T increased gradually during spermatogenesis from September to December (0.14+-0.06-0.26+-0.10 ng/mL) and peaked in January (0.36+-0.29 ng/mL) when the spermatozoa filled the testis. 11-KT also rose markedly in January and then decreased. On the other hand, 17 alpha 20 beta OHP in males did not show any clear tendencies.