Brainless sponges contain early echoes of a nervous system

Amazing stuff! Some of this research is still speculative.

"... Sponges, which are humans’ very distant evolutionary relatives, don’t have nervous systems. But a detailed analysis of sponge cells turns up what might just be an echo of our own brains: cells called neuroids that crawl around the animal’s digestive chambers and send out messages ...
The team suspects that these neuroids were sending signals to the cells charged with keeping the sponge fed, perhaps using vesicles to stop the movement of usually undulating cilia. If so, that would be a sophisticated level of control for an animal without a nervous system. ..."

From the abstract:

"The evolutionary origin of metazoan cell types such as neurons and muscles is not known. Using whole-body single-cell RNA sequencing in a sponge, an animal without nervous system and musculature, we identified 18 distinct cell types. ... Our data show a communication system that is organized around sponge digestive chambers, using conserved modules that became incorporated into the pre- and postsynapse in the nervous systems of other animals."

Brainless sponges contain early echoes of a nervous system | Science News Cells crawling around digestive chambers might help coordinate feeding

Profiling cellular diversity in sponges informs animal cell type and nervous system evolution (no public access)