Fundamental mechanisms of viviparity in some teleost fishes

本研究旨在通过组织学方法研究特氏石斑鱼（Achtes taczanowskii）雌雄个体的季节性生殖周期，以阐明特氏石斑鱼（Achtes taczanowskii）和特氏石斑鱼（Achtes taczanowskii）两种石斑鱼胎生现象的生理机制。根据四个种的生殖周期的比较，这是建议，北方种的倾向，延长配子发生在两性中，和精子在卵巢中的存储也倾向于在北方比在南方的物种更长。体外孵育实验表明，17 α，20 β-二羟基-4-异戊烯-3-酮（17 α，20 β-DP）在诱导卵母细胞成熟方面具有最显著的效果。此外，研究了生殖周期中血清类固醇激素水平的变化。提示雌二醇-17 β是参与卵黄发生的最重要的激素，17 α，20 β-DP可能在妊娠中起重要作用 ...更多信息 i和大理石.在两种卵生硬骨鱼，Oryzias latipes和Gasterosteus aculeatus，另一方面，受精和早期胚胎发育的实验可以诱导其卵巢人工授精后。这些结果表明，母体方面的生理创新，这与维持胚胎发育在妊娠后期和诱导分娩有关，可能是成功实现胎生的关键。faczanowskii的鉴定和部分特征的免疫化学程序。这表明，在多种FSSP中，卵黄蛋白原仅用于卵巢卵母细胞的卵黄形成，而不是妊娠期胚胎发育的直接营养来源。taczanowskii和S. Schlegeli，形态学和组织化学证实，发育中的胚胎在妊娠晚期通过其后肠摄取蛋黄样物质。在同一时期，这两个物种的胚胎中的Na，K-ATPase活性水平的增加。此外，在卵巢组织中观察到的一些超微结构特征表明，可能的潜在生理机制与维持妊娠的卵巢。少

The present research was planned to elucidate physiological mechanisms supporting phenomena of viviparity in some rockfish species of the genera Sebastes and Sebastiscus.Seasonal reproductive cycles were examined histologically in male and female Sebastes taczanowskii. On the basis of a comparison of reproductive cycles among four Sebastes species, it was suggested that the northern species tended to prolong gametogenesis in both sexes, and that sperm storage in the ovary also tended to be longer in the northern than in the southern species. In vitro incubation experiments revealed that 17alpha, 20beta- dihydroxy-4-pregnen-3-one (17alpha,20beta-DP) had the most significant effect in inducing oocyte maturation. Furthermore, changes in serum steroid hormone levels were studied during the reproductive cycles. It was suggested that estradiol-17beta was the most important steroid involved in vitellogenesis and 17alpha,20beta-DP possibly played an important role in gestation in S.taczanowski … More i and Sebastiscus marmoratus. In two oviparous teleosts, Oryzias latipes and Gasterosteus aculeatus, on the other hand, fertilization and early embryonic development could be experimentally induced in their ovaries after artificial insemination. These results indicate that physiological innovation on the maternal side, which is concerned with the maintenance of embryonic development during late pregnancy and the induction of parturition, may be essential for successful attainment of viviparity.Female-specific serum proteins (FSSPs) in S. faczanowskii were identified and partially characterized by immunochemical procedures. It was suggested that, among multiple FSSPs, vitellogenin was used only for yolk formation in ovarian oocytes and was not a direct nutritional source for developing embryos during gestation.In S. taczanowskii and S. schlegeli, it was confirmed morphologically and histochemically that developing embryos ingested yolk-like materials through their hindgut during late pregnancy. An increase in levels of Na,K-ATPase activity during the same period was observed in embryos of these two species. Furthermore, some ultrastructural features observed in ovarian tissues suggested possible underlying physiological mechanisms correlated with the maintenance of pregnancy in Sebastes. Less