Evolution of the nucleolar apparatus during oogenesis in Acipenseridae.

Evolution of the nucleoli has been followed during oogenesis in the Acipenserid fishes, Acipenser ruthenus (the sterlet) and A. guidenstadti (the sturgeon) using light and electron microscopes. In the ovaries of adults, the oogonial nuclei usually have a single nucleolus with an adjacent mass of paranucleolar fibrillar material. The cytoplasm of the oogonia contains two dense bodies peculiar only to gonocytes, one being electron dense and containing RNA and the otherbeing electron-lucent and lacking RNA...