자연산 문치가자미 (Limanda yokohamae)의 난소 발달에 따른 혈중 성호르몬과 난황단백전구체 농도 변동

Abstract

This study correlated changes in estradiol-l7<TEX>$\beta$</TEX> (<TEX>$E_2$</TEX>), testosterone (T), 17<TEX>$\alpha$</TEX>,20-dihydroxy-4-pregnen-3-one (DHP), and vitellogenin (VTG) levels with changes in the gonadosomatic index (GSI) and ovarian histology during the annual reproductive cycle of the wild marbled sole, Limanda yokohamae. Synchronous oocyte development occurs in this fish. Ovary maturity was classified into four periods, based on histological observations: the spawning (December to February), post-spawning (February to April), recovery (May to August), and vitellogenic (September to November) periods. Seasonal changes in the GSI were inversely correlated with water temperatures and reflected the degree of ovarian maturity. Plasma VTG levels were correlated with changes in the GSI, which increased from September to a peak in January, and levels remained comparatively high until February. Estradiol-17<TEX>$\beta$</TEX> was at baseline levels (<0.11 ng/mL) during the spring and summer, and peaked rapidly (1.55<TEX>$\pm$</TEX>0.445 ng/mL) from October to January. Plasma T and DHP levels had a similar profile; they rose markedly during the spawning period and remained low (or were not detectable) from spring through autumn. These data indicate that changes in plsama steroid hormones and VTG levels are correlated with the annual ovarian activity of the marbled sole. Based on these results and published reports, it appears that in this species DHP is the most important maturation-inducing steroid and that T is also related to final maturation.