An ultrastructural study of the ovary cord organization and oogenesis in Erpobdella johanssoni (Annelida, Clitellata: Hirudinida)

► Ovaries of Erpobdella johanssoni are composed of the ovisac and 7-8 ovary cords. ► Ovary cords are of 'Erpobdella' type, at their tip the apical cell occurs. ► Ovary cords are composed of germline cysts associated with somatic cells. ► Each germ cell in a cyst has one ring canal connecting it to the cytophore. ► Within oocyte nucleus a karyosome is formed during previtellogenesis.