拟穴青蟹受精膜形成过程中环形颗粒的发生与胞吐

为了揭示拟穴青蟹受精膜形成机制，采用透射电子显微镜研究了其受精膜形成过程中环形颗粒的形成与胞吐。结果显示，拟穴青蟹精子入卵后，发生皮层反应而形成受精膜。皮层反应包括致密颗粒首先胞吐以及环形颗粒的相继多轮胞吐。每轮环形颗粒的胞吐参与到受精膜的平缓期、增厚期和举起期3个阶段。环形颗粒的形成主要发生在受精膜的增厚期，受精卵的皮层和靠近皮层的内质中都在形成大量的环形颗粒，并且迅速移至皮层质膜附近发生爆发性胞吐，参与到受精膜的快速形成中。环形颗粒的形成与2种卵黄颗粒以及脂滴密切相关，在皮层中发现了线粒体参与其中，推测在拟穴青蟹受精卵的皮层和内质中可能存在环形颗粒合成的两套不同机制。研究表明，卵黄颗粒、脂滴及环形颗粒在拟穴青蟹受精膜形成过程中发挥重要作用。

Development and exocytosis of the ring-shaped granules during fertilization membrane formation in Scylla paramamosain

The development and exocytosis of the ring-shaped granules (RG) during the process of fertilization membrane (FM) formation in Scylla paramamosain were investigated by transmission electron microscope. The results are as follows: FM, the second envelope between oocyte and chorin, formed during a complex cortical reation initiated after fertilization. The cortical reation includes the successive exocytosis of two morphologically different granules. Firstly the dense granules underwent exocytosis and formed a thin membrane. After that, RG underwent several rounds of massive and rapid exocytosis, and the material from RG fused and formed a thick membrane. Every round of exocytosis of RG participated in three stages as the placid, the thickening and the swelling of FM. The development of RG happened both in the cortex and the nearby endoplasm mainly at the thickening phase of FM. Numerous RG formed and shifted to the edge of plasm membrane to participate in FM formation by explosive exocytosis. Our study showed that the development of RG was closely connected with two kinds of yolk granules and lipid drops, and mitochondria only appeared at cortex. So we inferred that there may be two kinds of RG forming mechanics in cortex and endoplasm in S. paramamosain. Finally, FM was composed of the two layers, and the newly formed plasma membrane became an inlaying membrane (the third envelope). The importance of yolk and lipid drops and RG in participating in FM formation was discussed at the end of this paper.