More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, leaving openings at both ends that become the mouth and anus.
22.
The defining characteristic of the deuterostome is the fact that the blastopore ( the opening at the bottom of the forming gastrula ) becomes the anus, whereas in protostomes the blastopore becomes the mouth.
23.
The defining characteristic of the deuterostome is the fact that the blastopore ( the opening at the bottom of the forming gastrula ) becomes the anus, whereas in protostomes the blastopore becomes the mouth.
24.
In animals at least as complex as earthworms, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut.
25.
If this region is surgically removed from the embryo, gastrulation does not occur at all . ?-Catenin also plays a crucial role in the induction of the blastopore lip, which in turn initiates gastrulation.
26.
It is thought that a network of filamentous actin in the yolk might constrict in a myosin-II dependent manner to close the blastopore at the end of epiboly, via a " purse-string mechanism ".
27.
While some animals develop the mouth and anus by deepening the blastopore, a " dent " in the surface of the early embryo, the blastopore of brachiopods closes up, and their mouth and anus develop from new openings.
28.
While some animals develop the mouth and anus by deepening the blastopore, a " dent " in the surface of the early embryo, the blastopore of brachiopods closes up, and their mouth and anus develop from new openings.
29.
There have been suggestions that the blastopore started out as the digestive surface on a radial organism, which became elongated ( and thus bilaterially symmetrical ) before its sides closed over to leave a mouth at the front and an anus at the rear.
30.
After the coalescence of the neural folds over the anterior end of the primitive streak, the blastopore no longer opens on the surface but into the closed canal of the neural tube, and thus a transitory communication, the neurenteric canal, is established between the neural tube and the primitive digestive tube.
