ULTRASTRUCTURAL INVESTIGATION OF SPERMIOGENESIS IN RHYNCHONELLA-PSITTACEA (TENTACULATA, BRACHIOPODA)

The spermiogenesis of the brachiopod Rhynchonella psittacea was studie d. The acrosome develops from cup-shaped acrosomal vesicles near the G olgi complex in the basal part of the spermatid. The acrosome vesicle then migrates to the apical region of the cell. The periacrosomal subs tance appears between the acrosomal vesicle and the nucleus. A ring-sh aped mitochondrion is localized around the basal part of the nucleus. During spermiogenesis the proximal centriole is in contact with the nu cleus via a single pericentriolar element. A distal centriole of the l ate spermatid has nine elements in a pericentriolar complex. The tail flagellum has a normal axonemal complex (9 + 2).