圆斑星鲽精子的超微结构及核前区特殊结构

分别以扫描电镜和透射电镜方法研究了圆斑星鲽 (Veraspervariegates)精子的超微结构。头部呈圆形、中段不发达 ,具有多个未分化的圆形小线粒体、鞭毛结构极简单 ,具有 9 2型的轴丝等特征 ,均表示圆斑星鲽的精子属于简单的原始类型 ,与多数其它高等鱼类精子结构相似。但是 ,圆斑星鲽精子核前部的凹陷 ,即不含染色质的电子透明区 ,以及核前区的囊泡结构却未见在其它新鳍鱼类精子中报道。圆斑星鲽精子核前凹陷开口于核前端稍偏处 ,凹陷呈不规则状 ,可深入到核的中央。凹陷处与染色质区无界膜分隔。凹陷区的前部及其开口处常有多个小的具单层界膜的囊泡 ,有时可见在凹陷区的开口处汇集成一个大泡。在某些处理过程中 ,例如在冷冻 -解冻过程中 ,囊泡可能丢失 ,而在精子顶端留下一个凹坑。尽管顶体在现存最早的新鳍鱼类 ,如雀鳝鱼及弓鳍鱼中已经完全消失 ,但考虑甚至在某些纯真骨鱼 ,如鲑形目中的螈鱼精子上 ,顶体仍然存在 ,而在其它一些纯真骨鱼精子或精子细胞中也存在顶体或顶体遗迹等事实。我们推测在圆斑星鲽精子中的上述特殊结构也是顶体的一种遗迹 ,但也不排除其是向外释放核内物质的一种途径的可能性

Fine structure of spotted halibut Verasper variegates spermatozoon with particular reference to the anterior vesicle and pit of the nucleus

The fine structure of spotted halibut Verasper variegates spermatozoon was studied with scanning and transmission electron microscopy. The spherical head, the reduced midpiece with numerous round unmodified small mitochondria,and the typical'9 + 2'pattern of the flagellum with quite simple structure, mean that the spermatozoon of spotted halibut can be considered to be of a primitive type, which is found in most of the advanced fish taxa. But the anterior vesicles and pit of the nucleus of this spermatozoon are seldom reported from other species. Anterolateral to the nucleus, there is a chromatin-free, electron-lucent area, that we named the anterior pit of the nucleus. Within and in front of the pit are vesicles of different size that are encapsulated in a layer of membrane. In some treatment, such as freeze-thawing, the vesicles can be lost, leaving a pit anterior to the head. With regard to acrosome and acrosome vestige present in some other euteleosts, we presume the vesicles represent acrosome vestiges though they may also function to release nuclear materialActa Zoologica Sinica 50 (4): 630- 637, 2004].