GERM-CELL CLUSTER FORMATION AND OOGENESIS IN THE HYMENOPTERAN COLEOCENTROTUS-SOLDANSKII

During first stages of oogenesis in an ichneumonid wasp Coleocentrotus soldanskii, in each 32 cell cluster, as many as 8 cystocytes enter me iosis. Only one differentiates as an oocyte, the rest are gradually tr ansdetermined to become nurse cells. Significantly, the nurse cells th at have passed the first stages of meiosis retain some features charac teristic of the oocyte. Namely the nuclei of these cells, as the oocyt e nucleus, produce accessory nuclei (AN). Gradual transdetermination o f pro-oocytes into nurse cells and the occurrence of ANs in transdeter mined cells suggest that a diffusing substance, forming a concentratio n gradient, is responsible for the determination of the oocyte within the cystocyte groups in hymenopterans.