Ultrastructure of Spermatogenesis of Syndisyrinx-Punicea (Hickman, 1956) (Platyhelminthes, Rhabdocoela, Umagillidae)

Abstract

Spermatogenesis of Syndisyrinx punicea is described. Spermatogonia are little differentiated, with few organelles and inclusions: polyribosomes, ribosomes, small round mitochondria with few cristae and some endoplasmic reticulum. Primary spermatocytes are large and contain multivesicular bodies that are also found in the cytoplasm of spermatids in greater numbers. Spermatids contain Golgi complexes consisting of a series of concentric circles, and numerous membrane-bound, rod-shaped electron-dense bodies. A zone of differentiation develops with peripheral microtubules, followed by the appearance of a prominent intercentriolar body. Two axonemes grow out in opposite directions from centrioles adjacent and perpendicular to the intercentriolar body. The area of differentiation protrudes and elongates to form the sperm shaft into which the nucleus and mitochondria migrate. Typical rootlets were not observed, although rod-shaped structures situated on each side of the nucleus, seen in one section, may be rudimentary rootlets. Spermatocytes and spermatids are linked by different kinds of cytoplasmic bridges. Spermatogenesis of S. punicea is compared with that in other groups of turbellarians and Neodermata.