2 . sperm ultrastructure the sperm is nonflagellated and composed of a main body in which including nucleus n apical cap and a little cytoplasm and a single spike extending from the convex surface of the apical cap , which consists of about twenty radial fibrillae on which exhibiting periodic cross - striations . the concave surface of the apical cap surrounds the little cytoplasm which is highly condensed and has n ' t any organella and sperm nucleus , which is uncondensed and composed of filamentous materials and many membrane - bound vesicles 外形呈图钉样，由主体部和棘突组成，主体部包括帽状体、细胞质带和精核。帽状体由约20根辐射状排列的纤丝组成，纤丝具横纹。其凸面延伸成棘突，棘突内纤丝是帽状体内纤丝的延续，亦具横纹。
