Talk:Protostome/Archives/2024/March

First Thread

Temporarily removed:

In both protostomes and deuterostomes, the embryo consists of a little ball of cells known as a blastula. Protostomes have their early cell divisions diagonal to the polar axis forming a spiral arrangement of cells; this is called spiral cleavage. A groups of cells move inward to form an opening called the blastophore, which in protostomes develops into the mouth.

Protostomes have a determinate cleavage: the fate of how each embryonic cell will turn out to be or function is typically fixed very early; the first four cells are separate and each will develop into a fixed quarter of the larva. If a cell is removed from the blastula, a limb might not form, for the other cells don't compensate. Protostomes are schizocoely, where the mesoderm splits and the split widens into a cavity that becomes the coelom.

This is because it doesn't seem accurate. Although many protostomes have spiral cleavage, it's not universal to the group, and in particular is rare among the Ecdysozoa. I'm not sure about the rest, but I thought it worth erring on the side of caution. Josh

I am curious to know what evidence there is for the assertion that it appears that the protostomes evolved from the deuterostomes, and that therefore protostomy is the derived condition. ???

 You're correct, protostomes did not evolve from deuterostomes, I will remove this now.