ULTRASTRUCTURE OF THE SPERMATOZOA OF 5 SPECIES OF SOUTH-AFRICAN BIVALVES (MOLLUSCA), AND AN EXAMINATION OF EARLY SPERMATOGENESIS

Transmission electron microscopy of the spermatozoa of five species fr om three families of bivalves has shown that each species has a sperm with unique morphology. However, the morphology of the acrosomes of ea ch species is typical of the subclass of bivalve to which they belong. An examination of spermatogenesis in the five species, along with a r e-examination of material from six other species of bivalves, has reve aled that pre-spermiogenic cells possess flagella. In addition, acroso me formation begins in the spermatocytes with the formation of proacro somal vesicles in the Golgi body. During spermiogenesis the proacrosom al vesicles coalesce at the presumptive posterior of the spermatid, wi th a larger vesicle produced by the Golgi body. The single acrosomal v esicle eventually migrates to the anterior of the spermatid where it a ssumes its mature form. (C) 1994 Wiley-Liss, Inc.