Fig. 4

Ovarian ultrastructure at the DE stage; a, b oocyte cortex without chorion (black arrow). Cytoplasm filled with immature and mature yolk vesicles, with many lipid droplets; c different compaction stages of the endogenous yolk vesicles (1, 2 and 3). Note the presence of endocytic vesicles in the oocyte cortex (white arrow); d endogenous yolk vesicles received small endocytic vesicles by fusion (black arrow). Notice the absence of ribosomes attached to the membrane; e f fusion between the endogenous yolk vesicles (white arrows). Immature and mature yolk vesicles surrounded by the membrane unit (black arrows); g Microvilli (black arrow) between the chorion and oocyte cortex showing endocytosis; h endocytic coated vesicle (white arrow). 1. Endogenous yolk vesicle with luminal material, 2. endogenous yolk vesicle with finely electron-dense material, 3. endogenous yolk vesicle with granular material, C chorion, EV endocytic vesicle, LI lipid droplet, Y1 immature yolk vesicles, Y2 mature yolk vesicles