The first embryonic opening that develops into the mouth in protostomes is called the Blastopore.
Explanation:
1. During the early stages of embryonic development in protostomes, a blastopore forms.
2. The blastopore is an opening in the early embryo that eventually develops into either the mouth or the anus.
3. In protostomes, which include organisms like insects, mollusks, and annelids, the blastopore develops into the mouth, making it the first embryonic opening.
4. This process is in contrast to deuterostomes, where the blastopore develops into the anus instead of the mouth.
So, in the context of protostomes, the blastopore is the first embryonic opening that will become the mouth during development.
