Electron microscopic study on oocytes, nurse cells and yolk formation in Leptestheria dahalacensis (Crustacea, conchostraca)

Electron microscopic study of Leptestheria dahalacensis reveals that the oocyte and its three nurse cells are interconnected by intercellular bridges. Along the contact zone between the plasma membranes of two adjacent cells dcsmosomes and a few gap junctions are visible. In the early stages of vitellogenesis the four cells (enclosed in a follicle) reveal similar nuclear and cytoplasmic ultrastructural features and similar synthetic activity, all four producing two types of yolk globules. The oocyte alone then develops numerous microvilli reaching towards the follicle cells and completes the vitellogenesis. Some pinocytotic vesicles are formed in the oocyte plasma membrane at this time. The protein yolk appears to be of mixed origin, with a much smaller exogenous component. The nurse cells are unable to develop microvilli towards the follicle cells (but not towards the oocyte), and therefore seem to be unable to incorporate protein yolk from the hemolymph. The results of the present ul...