Fundamental mechanisms of viviparity in some teleost fishes

本研究旨在阐明支持岩鱼胎生现象的生理机制。对塔萨诺夫斯基岩鱼和塔萨诺夫斯基岩鱼的季节性繁殖周期进行了组织学研究。通过对4个种的生殖周期的比较，认为北方种的雌雄配子发生均有延长的趋势，卵巢中精子的储存期北方种也比南方种长。体外培养实验表明，17α，20β-二羟基-4-孕烯-3-酮(17α，20β-DP)诱导卵母细胞成熟的效果最显著。此外，还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-17β是参与卵黄发生的最重要的类固醇，17α，20β-DP可能在…的受孕过程中起重要作用。More I和Sebastiscus marmoratus。另一方面，在两种卵生硬骨鱼中，通过人工授精，可以在卵巢中实验诱导受精和早期胚胎发育。这些结果表明，母体侧的生理创新可能是成功获得胎生的关键，而母体侧的生理创新与妊娠后期胚胎发育的维持和引产有关。在多种FSSP中，卵黄蛋白原仅用于卵巢卵母细胞的卵黄形成，而不是孕期发育胚胎的直接营养来源。在塔萨诺夫斯基和施莱格利，形态和组织化学证实发育中的胚胎在妊娠后期通过其后肠摄取类卵黄物质。在这两个物种的胚胎中，Na，K-ATPase的活性水平在同一时期都有增加。此外，在卵巢组织中观察到的一些超微结构特征表明，可能与Sebases维持妊娠相关的潜在生理机制。较少

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