帘文蛤精子超微结构及与其他双壳贝类的比较

Ultrastructure of spermatozoon in Meretrix lyrata and comparision with other bivalves

利用扫描电镜和透射电镜技术,详细观察了帘文蛤(Meretrix lyrata)精子的形态和超微结构.研究发现,帘文蛤的精子为典型的原生型,全长42.2±1.8μm,包括头部、中段和尾部三部分.头部为稍弯曲的狭茧形,长约2.4μm,由前端的顶体和其后的细胞核组成,顶体呈倒"V"形,前端电子密度较小,后端电子密度较大;核内含有高度浓缩的染色质,可见染色较浅的核泡存在,无核前窝,有明显核后窝和植入窝.中段由5个呈辐射状排列的线粒体和中央的2个相互垂直的中心粒复合体构成,线粒体近球形,由内、外两层膜组成.尾部鞭毛长39.3±1.9μm,由波浪状质膜和包裹其中的轴丝组成.另外,将帘蛤科(Veneridae)尤其是文蛤属(Meretrix)贝类精子超微结构与其他贝类进行了比较和分析,为文蛤属的种类鉴别提供细胞学依据.

The morphology and ultrastructure of spermatozoon of Meretrix lyrata were observed under scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.The study shows that the sperm of M.lyrata,having 3 parts of head,middle piece and tail,is a typical primitive form with a total length 42.2±1.8 μm.The head,like a narrow cocoon in shape,is comprised of acrosome and nucleus.The acrosome,which displays higher density in posterior part and lower density in anterior part,is upside-down V-shaped.The nucleus is mainly made up of highly enriched chromatin,nevertheless lighter dyed structure is also found.Implantation fossa and posterior nuclear fossa can be observed obviously in the posterior part of nucleus.However,anterior nuclear fossa is absent.The centriolar complex which is comprised of 2 orthogonal centrioles and 5 surrounding oval mitochondria constitute the middle piece of spermatozoon.Mitochondrion,formed by 2 membranes,is almost spherical in shape.Flagellum（39.3±1.9 μm in length） in tail is constituted by wavy plasma membrane and axoneme.In addition,we also compared and analyzed the difference between Veneridae,especially Meretrix,and the others,aiming to provide cytology evidences for species identification of Meretrix.