Ultrastructural study of the ovary and oogenesis of Polyonchobothrium clarias Woodland, 1925 (Cestoda: Bothriocephalidea) infecting Clarias gariepinus from Egypt.

Abstract

The ovarian tissues and different stages of oocytes development of Polyonchobothrium clarias Woodland, 1925 recovered from the intestine of Clarias gariepinus Burchell, 1822 fish was investigated by transmission electron microscope (TEM). The ovarian follicles are enveloped by compressed epithelial sheath lying on basal layer that shows epithelial projection into the lumen of each follicle. The epithelial sheath filled with glycogen, mitochondria and solitary lipid droplets. The epithelial nuclei are appeared closed to the basal part of the ovarian follicle. Numerous heterogeneous electron dense myelin-like bodies observed within the ovarian cytoplasm they appeared different irregular shaped. Each ovarian follicle contains number of oocytes loosely packed within the follicle at different stages of differentiation developmental stages starting with oogonial cells, primary, secondary and mature oocytes. The Oogonia were undergoing characteristic cytological changes that lead to oocyte maturation. Vitelline material appears in early stages of primary oocytes. Lipid droplets appeared in late stages of secondary oocyte. Mature oocytes are filled with clusters of cortical granules adjacent to the oocyte plasma membrane. Syncytial interstitial tissue and number of myelin-like bodies are observed in the ovarian cytoplasm and they fill the cytoplasmic spaces. The results of the present study were compared with the previous reports in other cestode taxa, to define the ultrastructural observations of the female reproductive tissues for clarification the reproductive fecundity of the parasite.