半滑舌鳎胚胎发育中后期卵黄囊超微结构观察

The Ultrastructure of the Yolk Sac in the Middle to Late Embryonic Stages of Cynoglossus semilaevis

在胚胎发育中期,半滑舌鳎胚胎由胚体、卵黄囊和卵周液构成。对半滑舌鳎胚胎发育中后期的卵黄囊进行超微结构观察。结果表明,卵黄囊是由卵黄囊膜和包裹其内的卵黄物质组成。在半滑舌鳎胚胎发育过程中,卵黄囊内的卵黄物质逐渐消耗产生低分子量的卵黄磷蛋白分裂小泡。分裂小泡转移到卵黄囊内部消黄细胞中,在消黄细胞的作用下分裂小泡转化成卵黄颗粒。随后卵黄颗粒在卵黄囊内表面聚集成囊状结构并转移运输到卵黄囊膜内部,最后把卵黄物质从卵黄囊膜转移并释放到卵周液中,为胚胎发育提供营养。

In mid-embryogenesis of Cynoglossus semilaevis,the zygote comes to be comprised of three distinct districts：the embryo proper,the yolk sac and the perivitelline fluid.The yolk sac was examined ultrastructurally in the middle to late embryonic stages.The results show that the yolk sac consists of the yolk sac membrane and its content of yolk.During embryonic development,the yolk sac declines in protein concentration due to vitellin undergoing limited proteolysis to yield a number of vitellin cleavage products of lower molecular weights.While they are gradually transferred to the cytosolic spaces of the vitellophages and transformed into yolk granules by intervention of vitellophages.The yolk granules assembled into yolk granule vesicles at the inner epithelium of the yolk sac and eventually,yolk granules are transferred to the perivitelline fluid via transcytosis through the yolk sac membrane to nourish the embryo.