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

摘要

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 material [ Acta Zoologica Sinica 50(4): 630 - 637 , 2004].