嘉庚蛸精子发生的超微结构

Ultrastructure of spermatogenesis of Octopus tankahkeei

应用透射电镜技术研究嘉庚蛸精子发生过程中各阶段细胞的形态、细胞器及细胞核的动态结构变化。精原细胞呈椭圆形,细胞质少、核大,有线粒体、高尔基体等细胞器;初级精母细胞呈圆形或卵圆形,线粒体多,索条状内质网发达,高尔基体常集中分布,中心粒形成;次级精母细胞呈圆形、椭圆形或不规则形,线粒体嵴发达、基质丰富,高尔基囊泡积累电子致密物,中心粒发出的“9+2”轴丝结构形成。精细胞分化过程分为6个时期,主要特点为:①核内染色质凝集经颗粒化、纤维化及片层化,最后,形成高电子密度的均质结构;与此相应,核形态由椭圆形、变成长椭圆形、再变成细长柱状,核后端最后向前凹入形成核内沟;精子核的形态建成为染色质的凝集与核周微管加压协同作用的结果。②高尔基囊泡积累电子致密物、融合发育成顶体囊,逐渐延长演变成钻头形的顶体。③线粒体向核后端迁移,形成精子尾部的线粒体鞘。

The morphological features of spermafids at different stages, and the structural dynamic changes of organelle during spermatogenesis of Octopus tankahkeei were investigated by transmission electron microscope. Spermatogonium is elliptic in shape with large nucleus. Less mitochondria and Golgi bodies in cytoplasm of spermatogonium. The primary spermatocyte is round or oval in shape, with more mitochondria in cytoplasm. The endoplasmic reticulum is more developed and is rope-like in shape, and the Golgi bodies accumulated and the centriole is also seen in the cytoplasm in the primary spermatocyte. The secondary spematocyte is round, elliptic or irregular in morphology. The cristae in mitochondria in the secondary spermatocyte are well developed, and the matrix of mitochondria is rich; also the electron density materials were accumulated in Golgi vacuoles and the ＂9 ＋ 2＂ arrangements of axoneme are extended from centriole at this stage. The spermiogenesis can be divided into 6 continuous steps based on the morphological changes of acrosome, nucleus and mitochondria. Three main events happen during spermiogenesis. （ 1 ） The chromatin in spermafid undergoes a process of granulation, fibrosis, and stratification, and finally is highly condensed with high electron density. At the same time, the morphology of nucleus changes gradually from ellipse, and long ellipse to slim column. Endonuclear channel was formed by the concave of the posterior nucleus. The coagulation of chromatin and the pressure posed by peri-nuclear microtubules help the formation of the morphology of the nucleus. （2） Golgi vacuoles accumulate density materials, fuse into acrosoml vesicle, and finally, the pre-acrosome becomes an aiguiUe-like acrosome. The striations and spikes can be seen on acrosome. Endoplasmic reticulum also participates in acrosome biogenesis. （3） Mitochondria move posteriorly to the nucleus and form the chondriosomal mantle of the tail. The formation of the chondriosomal mantle is the biological adaption to internal fertilization of this species. Because of the long chondriosomal mantle, the sperm of Octopus tankahkeei supply more energy than the sperm of bivalves and Archaeogastropoda, the later undergo exterior fertilization. The features of six stages during spermiogenesis are summarized as follows： From stage Ⅰ to stage Ⅱ, the chromatin transforms from conglomeration to granulation, the later which distribute evenly in the nucleus, and also, the peri-nuclear microtubules appear, the posterior nuclear pocket invaginates deeply, the nucleus elongates, and the acrosomal vesicle heaves up; at the third stage, the chromatin is flocculent in shape. Endonuclear channels are formed; at the fourth stage, the chromatin is long fibroid in shape, acrosomal cone is formed; at the fifth stage, the chromatin become stratification, acrosomal vesicle is long cystiform in shape; at the sixth stage, the nucleus is long columned in shape, with condensed chromatin inside, acrosomal vesicle has developed to long cone acrosome and the chondriosomal mantle is formed at mid-piece of tail.