The blastula develops a pore at one end, called a blastopore. If that blastopore becomes the mouth of the animal, the animal is a protostome, and if it forms an anus, the animal is a deuterostome.

The blastula develops a pore at one end, called a blastopore. If that blastopore becomes the mouth of the animal, the animal is a protostome, and if it forms an anus, the animal is a deuterostome.

Animals often form either the mouth or the anus from an opening that appears in the early embryo, which is called the blastopore. For instance, starfish develop the anus from the blastopore ...

A molecular dissociation of both mouth and anus formation from the blastopore might explain why the site of mouth formation is distinct from the blastopore in the deuterostomes, and in many ...