Origin and fine structure of the germ-cell determinant in summer and winter eggs of Daphnia pulex and D. magna were studied. The germ-cell determinant appears in the perinuclear cytoplasmic region of the oocyte still undifferentiated from its nurse cells, and then it will migrate to the cortical ooplasm. The completely developed germ-cell determinant consists of a coarse network of fine granular and fibrillar material, which is extruded from the nucleus through the pores of the nuclear envelope. Vesicles of different size, some dense bodies and glycogen particles are enclosed in the meshes of this network.
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Con il contributo del Ministero per i Beni e le Attività Culturali