Natures wonders: making an octopus brain: (Introduction)

by David Turell , Wednesday, November 09, 2022, 22:29 (526 days ago) @ David Turell

Study covers all cephalopods:

https://phys.org/news/2022-11-squid-octopus-big-brains.html

"Cephalopods have the most complex brains of any invertebrates on the planet. What remains mysterious, however, is the development process. Basically, scientists have long wondered how cephalopods get their big brains in the first place. A Harvard lab that studies the visual system of these soft-bodied creatures—which is where two-thirds of their central processing tissue is focused—believe they've come close to figuring it out. The process, they say, looks surprisingly familiar.

***

"The neural stem cells they tracked behaved in an eerily similar manner to the way these cells behave in vertebrates during the development of their nervous systems. It suggests that vertebrates and cephalopods, despite diverging from each other 500 million years ago, are not only using similar mechanisms to make their big brains, but that this process and the way the cells act, divide, and are shaped may essentially lay out the blueprint required develop this kind of nervous system.

"'Our conclusions were surprising, because a lot of what we know about nervous system development in vertebrates has long been thought to be special to that lineage," said Kristen Koenig, a John Harvard Distinguished Fellow and senior author of the study.

"'By observing the fact that the process is very similar, what it suggested to us is that these two independently evolved very large nervous systems are using the same mechanisms to build them. What that suggests is that those mechanisms—those tools—the animals use during development may be important for building big nervous systems."

***

"This live-imaging technique allowed the team to observe stem cells called neural progenitor cells, and how they are organized. The cells form a special kind of structure called a pseudostratified epithelium. Its main feature is the cells are elongated so they can be densely packed. The researchers also saw the nucleus of these structures move up and down before and after dividing. This movement is important for keeping the tissue organized and growth continuing, they said.

"This type of structure is universal in how vertebrate species develop their brain and eyes. Historically, it was considered one of the reasons the vertebrate nervous system could grow so large and complex. Scientists have observed examples of this type of neural epithelium in other animals, but the squid tissue they looked at in this instance was unusually similar to vertebrate tissues in its size, organization and the way the nucleus moved."

Comment: for me it is just another example of genome convergence.