中文摘要：

通过电光学显微镜和透射电子显微镜观察了平疣桑椹石磺精子的形态及其超微结构。平疣桑椹石磺成熟精子属于进化型，由头部、中段和末段组成。头部由顶体和精核构成，顶体长约0.7μm，呈细奶嘴状，内含物分布均匀，电子密度稍低于细胞核。顶体基部与精核前端紧密相连，无间隙。精核长约3.8μm，宽约1.0μm，核质高度浓缩，电子密度高，无核泡，纵切似辣椒状，核后端内凹形成核后窝。中段加长，结构复杂，线粒体演化成线粒体鞘，螺旋状包绕轴丝。精子末段由轴丝及包绕轴丝的质膜组成，轴丝为典型的“9＋2”结构。比较了平疣桑椹石磺精子与相关腹足类精子结构的异同，进一步证实了腹足纲贝类精子结构之间的区别主要在于顶体有无及形态，精核的长短与外形、中段线粒体的数目及其排列方式等。

英文摘要：

The structural characteristics of mature spermatozoa of Platevindex mortoni were observed by light and transmission electron microscopy.P.mortoni sperm is of the modified type, the mature spermatozoon contains three parts：head, mid-piece and end-piece. The head comprised an acrosome and a nucleus.The acrosome is nipple-shaped, about 0.7μm in length.The electron density of the acrosome is less than nucleus, and the contents in the acrosome is homogeneous.There was no space between the acrosome and nucle-us.The nucleus is chili-shaped, about 3.8μm in length and 1.0μm in width.The caryoplasm is highly condensed, and there was no vesicle found in nucleus.There existed a posterior nuclear fossa at the end of nucleus.The elongated mid-piece was more complex. The filar mitochondria formed into chondriosomal mantle, and enwraps the elongated middle piece.The end-piece of the sperm consists of the axoneme and its surrounding cytoplasm,and the axoneme has a typical“9＋2” structure.The similarities and differences of the sperm ultruastructure between P.mortoni and some other related gastropods are discussed.The main difference between different spe-cies lie in the existence, the feature of acrosome, the shape and the length of nucleus, the number, morphology and the arrangement of mitochondria in the mid-piece.