Ultrastructure of the male reproductive system in a rumen amphistome Cotylophoron cotylophorum

The ultrastructure of various regions of the male reproductive tract and the prostate gland of Cotylophoron cotylophorum (Trematoda: Digenea) is described. The internal lining of the entire male duct system is syncytial in nature, and regional variation is quite evident. The syncytial epithelium of the vas deferens and seminal vesicle is very thin, flat and lamellate and the lumen is packed with spermatozoa. In the pars musculosa (PM) the syncytium is also flat but lamellae are sparsely distributed and anastomosed at places to form loops. The syncytium of the PM is invested by several layers of circular and longitudinal muscle. The pars prostatica (PP) is lined by an uneven but moderately thick syncytial epithelium with nuclei projecting into the lumen. The syncytium bears numerous very long lamellae. The ejaculatory duct epithelium is devoid of lamellae. It is even and moderately thick throughout. The prostate gland cells are uneven in outline and bear long ducts which open into the lumen of the PP. They show an ultrastructural organization suggestive of protein secretion.