Development of the oocyte and its accessory cells of the polychaete, <i>Diopatra cuprea</i> (Bosc)

Abstract

Abstract The oocyte‐nurse cell complex of the polychaetous annelid, Diopatra cuprea , has been explored by various methods of light microscopy and by the technique of electron microscopy. Early in its development the complex appears as a string of cells floating within the coelomic cavity. As this string of cells develops, the volume of one cell (approximately the middle one) increases greatly; while that of the remaining cells, referred to as nurse cells, increase slightly. Due to this differential growth, the two opposing strands of nurse cells are displaced to one side of the oocyte. Nurse cells are joined to one another by cytoplasmic bridges. Cytoplasmic bridges also exist between the strands of nurse cells and the oocyte. The presence of numerous ribosomes within the bridges between the oocyte and nurse cells encourages us to suggest that this organelle may be transferred to the oocyte via this route. The transported ribosomes may be used by the maturing oocyte, or they may be stored by the egg to be utilized during embryogenesis. Moreover, we believe that the nurse cells are not involved in the production of the protein‐carbohydrate yolk bodies for we think that these are elaborated by the endoplasmic reticulum in collaboration with certain Golgi complexes of the oocyte.