STUDIES ON THE MALE REPRODUCTIVE SYSTEM OF THE FRESHWATER PRAWN, MACROBRACHIUM NIPPONENSE: Ⅱ. THE MORPHOLOGY AND ULTRASTRUCTURE OF THE SPERM
QIU GAO-FENG (Fisheries College, Shanghai Fisheries University, Shanghai 200090) DU NAN-SHAN,LAI WEI (Deportment of Biology, East China Normal University, Shanghai 200062)
The sperm morphology of the freshwater prawn, Macrobrachium nipponense, was in- vestigated by electron microscopy and cytochemical methods. The samples were obtained from the vas deferens of the males and from the spermatophores attached to the ventral body wall of the naturally mated females during 1992-1993. The unistellate sperm of the prawn belongs to aflagellate sperm and resembles a thumb tack. The sperm consists of a main body and a spike. The main body can be distinctly divided into three structural regions: the cap-shaped region, the cytoplasmic band, and the nu- clear region. The cap-shaped region contains about 20 radial fibrils with cross striations. These fibrils converge at the base of the main body and extend to form the spike. The cyto- plasmic band is devoid of centrioles. The nuclear region can be further divided into a vesicu- lar zone and a membranous zone. Many PAS-positive vesicles, formed by pinocytosis of the spermatophore matrix in the vas deferens, characterize the vesicular zone near the concave side of the main body. The membranous zone is filled with membrane cisternae like endo- plasmic reticulum. The nuclear material is loose and shows positive reaction to Feulgen and Fast green. The nuclear envolope is incomplete and indistinct. The spike of the sperm, showing a negative reaction to PAS, does not contain acrosomal complex.