The structure of the ovary and oogenesis in the earthworm,Dendrobaena veneta (Annelida,Clitellata)

The structure of the ovary and the type of oogenesis were determined in the earthworm Dendrobaena veneta (Oligochaeta, Haplotaxida, Lumbricidae) with histological, electron-microscopic and immunocytochemical methods. In this species the ovary is of the alimentary, nutrimentary type because it contains oocytes and the nurse cells (trophocytes). The ovarian stroma is built by somatic cells, the processes of which are connected to each other via numerous desmosomes. The somatic cells and their processes envelop the germ cells tightly and play a supportive role. Oogonia, oocytes and trophocytes are arranged in distinct zones in the ovary. Trophocytes form chains of cells, which are interconnected by intercellular bridges. Numerous microtubules are located within the latter. The oocytes are distally arranged in the ovary. Vitellogenesis involves both auto- and heterosyntheses. The results obtained were compared with the reports on oogenesis in other representatives of Annelida.