Abstract:The ultrastructure of the spermatozoon of Scapharca broughtonii was observed with scan and transmission electron microscopy (SEM and TEM). The results of SEM demonstrated that the total length of spermatozoon was 55μm,composed of head,middle piece and tail.The head length of spermatozoon was 2 μm and the diameter was 1.5 μm at the maximum width.The results of TEM demonstrated that the head of spermatozoon consisted of acrosome and nuclear.The acrosome was in the front of head, somewhat obtuse and V-shaped upside down.A gap existed between the acrosome and the nuclear.The nuclear, in which there were posterior nuclear fossa and implantation fossa,without anterior nuclear fossa, was under acrosome and accounted for 2/3 of the head volume.The middle-piece was formed by centrosome which was revolved around by 5 oval-shaped mitochondrias.The long axis diameter of cross section at mitochondria was 0.6μm and the short axis diameter was 0.5μm. The flagellum was slender and consisted of tail fiber which was surrounded by plasma membrane,with an axoneme inside. The cross section was circular and its diameter was 0.15 μm, showing a typical “9+2” structure.
