THE FINE STRUCTURE OF THE MATURE SPERM OF THE FRESHWATER PRAWN, MACROBRACHIUM ROSENBERGII

¹ Department of Animal Science, University of California, Davis, California, 95616

Electroejaculated spermatophores from male Macrobrachium rosenbergii contain mature sperm which resemble everted umbrellas. The nonflagellated, nonmotile sperm consist of a 10 µm main body (base) and a single 12-15 µm spike extending from the convex surface of the base. The nucleus is flocculent (decondensed), contains basic proteins, is not delimited by a nuclear membrane, and is housed in the base. The cytoplasm of the convex base contains fifteen to twenty radial fibrils which anastomose to form the spike. Both the spike and the radial fibrils are cross-striated with a periodicity of 35 nm. These structures contain 6 nm filaments running perpendicularly to the cross-striations. A pair of centrioles composed of nine doublet tubules are located acentrically near the origin of the spike in the cytoplasm of the base. Radial fibrils are interconnected to the centriolar matrix by accessory fibrils. No clearly definable acrosomal region is identifiable morphologically or histochemically.