Abstract:The ultrastructure of barfin flounder Verasper moseri spermatozoon was studied with scanning microscopy and trans mission electron microscopy. Total length of the sperm is 45.57±3.23μm (n=11), and the sperm includes three parts: head, mid piece and flagellum. The spherical head mainly consists of the nearly circular cell nucleus. The mid piece is composed of mitochondria and center grain complex, with some round undifferentiated small mitochondria. The typical ‘9+2’ pattern of the flagellum has quite simple structure, which means that the spermatozoon of barfin flounder can be classified as 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 have seldom reported from other species. There is no acrosome in the sperm. At anterolateral to the nucleus, there is a chromatin free, electron lucent area, which was named the anterior pit of the nucleus. Within and in front of the pit, an irregular shaped structure and some different sized vesicles that are encapsulated in a layer of membrane were found. With regard to acrosome and acrosome vestige present in some other euteleosts, we presume that the vesicles may represent acrosome vestiges though they may also function to release nuclear material, while the irregular shaped structure in front of the nucleus may be caused by improper sample preparation
