锯缘青蟹精子发生的超微结构

ULTRASTRUCTURE OF SPERMATOGENESIS IN THE CRAB SCYLLA SERRATA

采用透射电镜观察锯缘青蟹精子发生过程中超微结构的变化。结果表明：精原细胞椭圆形，染色质分布于核膜周围，胞质中具嵴少的线粒体、内质网小泡等。初级精母细胞染色质呈非浓缩状，胞质中具众多的内质网小泡，特殊的膜系及晶格状结构。次级精母细胞核质间出现由内质小泡聚集成的腔。极化的早期精细胞前顶体腔形成，从其顶端分化出一致密的浓缩体。前顶体腔占据细胞的一极，另一极是核及细胞质，核呈均质，细胞质少，只剩膜系及少量的线粒体等。中期精细胞顶体腔基部及质膜内凹，膜系移入腔内形成拱形结构。拱形结构向顶体顶端推进与顶体腔顶端由浓缩体演变的顶体帽汇合形成顶体管。核体积扩大，染色质为细微丝结构。后期精细胞顶体进一步分化为顶体管和顶体囊。顶体囊分为头帽、亚头帽、内层和外层四个区，核呈辐射状延伸，至此精子近成熟。成熟精子顶体呈陀螺形，头帽分化成中间薄且透亮、内外较厚、电子密度较高的结构。中央管中的短管状结构有序堆集呈锥状，锥尖指向头帽。

Spermatogenesis in the crab Scylla serrata was examined using transmission electron microscopy. The spermatonium has an oval shape, in which there are dispersed chromatin, mitochondria and endoplasmic reticulum vesicles. The primary spermatocyte contains decondensed chromatin, a large amount of endoplasmic reticulum vesicles, special membrane system and crystalline lattices. In the secondary spermatocyte emerges a cavity which is formed by the aggregation of endoplasmic reticulum vesicles. The early polarized spermatid has a conspicuous proacrosomal vesicle at one pole, a dense apical condensate formed at the top of the vesicle. A homogeneous nucleus and some cytoplasm containing only the membrane system, mitochondria, etc. lie to the opposite pole. In the mid stage spermatid an invagination of the acrosomal vesicle membrane gives rise to the formation of the perforatorium, in which a shapeless tubule originates from the membrane system. The nucleus enlarges and the chromatin begins to arrange into fibers. In the late spermatid the nucleus differentiates into numerous slender arms, the spherial acrosome further develops into acrosomal tubule and acrosomal vesicle. The acrosomal vesicle includes an apical cap, a subcap zone, an inner layer and an outer layer. The mature sperm has a top like shape, the apical cap can be divided into three thin layers (two dense layers and one lucent layer). Outside of the outer layer are 2 3 lamellar structures. Microtubules of the perforatorium in the central cannal present a conical appearance.