Abstract: Spermatozoonal ultrastructure of Sakhalin surf clam Pseudocardium sachalinensis （Schrenck） was observed under electron microscopy. The observation shows that the spermatozoon of the clam posses flagellates, and has body of 45 - 51 μm and head length of 2.0 - 2.6 μm in scanning electron microscopy （SEM）. The mature spermatozoon consists of head, middle piece and tail under transmission electron microscopy （TEM）. The acrosome is conical in shape. Acrosomal materials with a lampshade -shaped structure lie around its base. The conical subacrosome space is filled with low density materials. There is an ellipsoidal nucleus with high electron density under an acrosome. The vesicles, one or several, were found in the unclear region. Two centrioles and four large ellipsoidal mitochondria form the middle piece. The centrioles are of cylindrical hollow construction surrounded by four mitochondria and separated from the basal plate of the tail. A satellite body was observed at the basal part of the distal centriole. The flagellum is a typical＂9 ＋2＂ microtubular structure lining with the cell membrane.
2006, Vol. 21 
