Oogenesis,Vitellogenesis and Cocoon Secretion in Two Freshwater Leeches from Assiut, Egypt

The organization of the ovisacs, fine structure of the oogenesis, vitellogenesis and formation of cocoons were studied in two freshwater leeches; Alboglossiphonia levis (Glossiphoniidae) and Barbronia assiuti (Barbronidae). Each of them was composed of two elongated ovisacs of germ cells' clusters. The ovisacs, in the studied species, were meroistic (nutrimental), without regionalization and mitotically dividing oogonia, germ cells entering the meiosis prophase as well as trophocytes, prominent cytophores and growing oocytes were occurred. During late previtellogenesis/early vitellogenesis, the oocytes detached from the cytophore and floated in the coelom; they are usually enveloped by the peritoneal epithelium and associated with blood vessels. Meantime, the activity of clitellar gland cells in both studied leeches could be distinguished. Both light and electron microscopy revealed two types of clitellar gland cells. These exocrine gland cells were responsible for the formation of cocoons which enclosed the fertilized ova. The organization of ovisacs and the course of oogenesis in the two genera were studied ultrastructurally and compared with other related leeches.