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:
- When apical constriction first begins, isolated cells can
be seen with constricted apices surrounded by other cells that
have not constricted yet.
- 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).
- Finally, rolling
of the vegetal edge of the dorsal
involuting marginal zone (DIMZ) takes place.
Onset of apical constriction: profile
Blastoporal groove: surface
view
Rolling of the blastoporal
lip