Ultrastructure of male reproductive system in three Proteocephalidean cestodes.
The ultrastructural studies of the male genital system in Gangesia parasiluri, Proteocephalus torulosus, and P. exiguus revealed that the duct lining was syncytial. The testes follicles were surrounded by an anuclear cellular sheath of flattened cells and intercellular matrix. The vas deferens [ductus deferens] and sperm duct had contraluminal invaginations, intraluminal protuberances, and cilia. The latter had intra-epithelial nuclei in the proximal part. The lining of the cirrus represents a distal cytoplasmic layer similar to the tegument. There were filamentous and blade-like microtriches on the cirrus surface in P. torulosus and P. exiguus, and branched filamentous microtriches in G. parasiluri. A ciliated sensory receptor was found among the microtriches lining the P. exiguus cirrus. The muscles forming the cirrus sac wall contain large myocytons that merge with myofibrils. In the G. parasiluri and P. torulosus cirrus sac, the unicellular prostate glands were located among flattened muscular processes. Their secretory processes were connected with the plasma membrane of the sperm duct by the desmosome. The morphology of the genital system in Proteocephalidea cestodes was found to be similar.