Rachel Sipler

So the tube feet are pretty stationary.

They don't move around, but they do restructure and reform a little bit.

The tentacles, on the other hand, when they were healing and surviving in natural seawater, they were actually continuing to move around and respond to their natural environment.

It almost looked kind of like they were trying to continue feeding.

And when we would poke them or move the water around them, then they would retract into themselves as though they were responding to maybe predator pressure or something like that.

So it seemed as though there was still a bit of neural function going on in these tentacles.

Almost a little bit like Thing from The Addams Family.

Yes, they kind of straddle that line between what is alive and what is dead.

Oh, man, I think this is opens up a lot of questions that still need to be explored.

And it honestly took us in a lot of maybe philosophical directions because they kind of defy some of those boundaries that we've put on why organisms exist.

want to be alive or the evolutionary advantage.

The fact that these organisms are persisting, they're demonstrating some of the key fundamental processes that keep tissues alive, but they don't reproduce, which is something we expect to see in living organisms.

And so they kind of exist in the gray zone a little bit.

Yes.

So one of the things that we looked at in this study was the presence of their immune cells, which in sea cucumbers are called coelomocytes.

And so we used histology to look at the internal organization of their tissues, and we saw that their immune cells were still there, and they were actually migrating through the tissues to specific sites.

So early on during the wound healing and regeneration, the immune cells migrated to the wound site and seemed to be helping with

cleaning, degrading tissues, and possibly preventing invasion by bacteria and things like that.

So they did grow in size a little bit, but I would say the most striking change was in their appearance.

So they went from looking as you would expect a tube foot to look, if you know what those look like, to reforming into a spherical shape.