Fig. 1. Distribution and reorganization of organelles, cytoplasm and cortex in Phallusia eggs and zygotes. Unfertilized egg (A); zygote, 3 minutes after fertilization (B); and zygote, 10 minutes after fertilization (C). The distribution of yolk platelets (blue) and mitochondria (green) in confocal sections 3 µm below the surface (A) or near the equator (B,C) oriented along the animal-vegetal (a-v) axis. The sperm aster region (sa, arrowhead) is a mitochondria-free, yolk platelet-free zone. In B, a contraction pole (cp) has formed. Bar, 23 µm. (D-F) The overall organization of the unfertilized egg (D); zygote, 3 minutes after fertilization (E); and zygote, 10 minutes after fertilization (F). ER network, red; yolk platelets, blue; mitochondria-rich domain, green; microtubules, green lines. Chromosomes (blue) are shown in the sperm aster, in the meiotic spindle and in the polar body (pb1). (G,H) Unfertilized egg: distribution of ER in confocal grazing tangential sections (1 µm (G) or 3 µm (H) below the surface) of an egg oriented along the animal-vegetal (a-v) axis. er, ER-rich domain; er arrow, corridor of ER-rich domain traversing the subcortical ER-poor and mitochondria-rich domain (m in green). (I) Unfertilized egg: distribution of cytosol visualized with injected Ca Green dextran (same egg and confocal section as that seen above in H). Yolk platelets are seen negatively as black round vesicles excluding the dextran dye. Bar, 15 µm.