中文摘要：

利用透射电镜和扫描电镜对文蛤精子的超微结构及精子入卵过程进行了详细观察。结果显示,文蛤精子为典型的原生型,由头部、中段和尾部三部分组成,全长45—50μm。头部呈狭茧形,长约3.0μm,由顶体和细胞核组成,顶体呈倒＂V＂字形,前端有短柱状的凸起;细胞核为稍弯曲的圆柱形,内含高度浓缩的染色质,无核前窝,有核后窝。中段较短,仅0.6—0.7μm,由线粒体围绕中心粒复合体构成,5个圆球形的线粒体呈单层梅花状排列,内部为双层膜折叠成的片层状结构;中心粒复合体由近端中心粒和远端中心粒组成,而远端中心粒延伸出尾鞭的轴丝。尾部为细丝状鞭毛,长约42—45μm,内部的轴丝呈典型的＂9＋2＂结构,外周有波浪状质膜包被。用扫描电镜观察了文蛤精子的入卵过程,大致将其分为顶体反应期、穿卵期和卵膜修复期。受精后2min,精子发生顶体反应,顶体泡破裂释放溶解酶使卵膜变得疏松,亚顶体腔中伸出的顶体丝先穿透卵膜;受精后4—6min,在精、卵的共同作用下,精子头部和中段逐渐穿过卵膜进入卵内,在卵膜上形成一个直径约1.5μm的孔道,而精子尾部则留于卵外;受精后8—10min,精子尾部脱落,受精形成的孔道被卵膜的微绒毛修复。另外对多种双壳贝类精子超微结构和线粒体入卵等问题进行了探讨。

英文摘要：

The ultrastructure of spermatozoon and the penetration into egg in Meretrix meretrix were observed carefully by both scanning and transmission electron microscopes. The results indicate that the mature spermatozoa （45—50μm in total length） were primitive type, consisting of head, middle piece and tail. The head, like a long cocoon in shape （3.0μm in length）, is composed of acrosome and nucleus. The acrosome is upside down V-shaped with a protruding short cylinder at the top. Nucleus are slightly curved with fine-grained dense chromatin, having posterior nuclear fossa but anterior ones. The centriolar complex, including proximal and distal centrioles, and surrounding 5 spherical mitochondrias, make up the short middle piece （0.6—0.7μm）. The tail, a whip-like flagellum （42—45μm in length）, consists of axoneme that is a typi- cal ＂9 ＋ 2＂ microtubular structure and wrapped by an wavy plasma membrane. The sperm penetration into the egg was observed under a scanning electron microscope. Like most of marine mollusks, three phases could be observed： acrosome reaction, penetrating, and vitelline membrane repair. Two minutes after fertilization, the sperm attaching to the egg induced acrosome reaction, and led to the breakdown of acrosome vesicle and release of hydrolase to loosen vitelline membrane for easy break. And then, the acrosome filament from subacrosome pierced into vitelline membrane. Four to six minutes later, the head and middle piece of sperm entered into egg cytoplasm, leaving a hole of 1.5μm in diameter at the vitelline mem- brane. Eight to ten minutes after fertilization, the tail fell off and the hole was repaired by microvilli. In addition, ultra- structure of spermatozoon and sperm mitochondria in various bivalves are discussed in this paper.