Gastrulation in Xenopus:

Apical Constriction of Bottle Cells

The scanning electron micrographs below demonstrate the behavior of bottle cells during formation of the dorsal blastopore lip in Xenopus. As bottle cells begin to form, they can be seen to undergo apical constriction. The sequence of images shows the following:
  1. When apical constriction first begins, isolated cells can be seen with constricted apices surrounded by other cells that have not constricted yet.
  2. As more cells constrict apically, the blastoporal pigment line is created, followed by the blastoporal groove. This period corresponds to the "dirty frown" visible on the surface of the embryo (see the preceding sections).
  3. Finally, rolling of the vegetal edge of the dorsal involuting marginal zone (DIMZ) takes place.

Rolling of the blastoporal lip

Onset of apical constriction: profile

Blastoporal groove: surface view