Ricerche citologiche sull'oogenesi del Baco da seta (Bombyx moriL.) e considerazioni sull'oogenesi degli Insetti

Abstract

Summary Bombyx mori L. has a polytrophic meroistic ovary. The follicles are formed by an oocyte and seven nurse cells. The oogenesis can be divide in three phases corresponding to the three periods of growth of the oocytes. The first period goes from the beginning of meiosis to pachytene; the second from pachytene up to the beginning of the yolk platelets formation; the third one is characterizided by storage of yolk platelets and ends with the egg matuturation. The second period of growth occurs mainly through the activity of the nurse cells. The nurse cells are, at first, undistinguishable from the oogonia, later they grow, polyploidize and produce, through a nucleus-nucleolar system, ribonucleo-proteins which flow in to the oocyte cytoplasm where protein synthesis occurs. Succesively the nurse cells degenerate, in the oocyte the formation of yolk platelets occurs and the third period of growth begins. The Caspersson's theory on the system of protein synthesis may be applied to the second period of grow...