Vitellogenesis of Rugogaster hydrolagi (Trematoda, Aspidogastrea)

Abstract

Vitelline follicles are surrounded by a basal lamina and fibrous matrix. Cytoplasmic processes of peripheral perikarya extend between the vitelline cells and into them. Immature vitelline cells have relatively little cytoplasm, many mitochondria, much rough endoplasmic reticulum, Golgi complexes and none or few yolk granules. Maturing vitelline cells have relatively more cytoplasm and contain large vacuoles with many dark grana, free ribosomes, much rough endoplasmic reticulum, lipid droplets, and many mitochondria. At later stages of maturation and in mature cells dense irregularly shaped inclusions and large interconnected spaces containing much α-glycogen are present. Intact vitelline cells are incorporated into the egg. Small vitelloducts are ciliated, have intraepithelial nuclei separated by lateral cell membranes, surface lamellae, and are surrounded by a basal lamina and fibrous matrix. Presence of perikarya in the vitelloducts separated by lateral cell membranes is characteristic of monogeneans and trematodes including the aspidogastreans, syncytial vitelloducts are synapomorphic for the Gyrocotylidea, Amphilinidea and Cestoidea.