TIL: These Spiny Sea Creatures Can Regrow Lost Body Parts | Today I Learned

There's an incredible group of animals out there called the echinoderms. They can actually regenerate a lost body part. So, a kind of derm essentially just means spiny skin, so derm like dermis, so skin, and a chi know is sort of spiny. So, sort of spiny skinned, it's sea urchins, sea cucumbers, brittle stars, and sea stars. They sort of all fall in this echinoderm group.

In general, the padded domes are filing with an incredible capacity for regeneration. If you're a sea cucumber, you know you don't move very fast, but if something's trying to get at you and you got to give them something interesting, sea cucumbers will actually eviscerate, essentially throw up their entire stomach, can then regrow that entire stomach tract. If you don't have a lot of abilities to make toxins, if you don't have an ability to make ink, you know you've got to find other ways to escape.

Take something like a brittle star; it can just drop off an arm in order to escape and regrow a new one. There's connective tissue holding the arm together, and so when it sort of senses this disturbance, something inherent says there's a problem, we need to escape. And so they will fight that arm tissue and just drop the arm and swim away.

You have this initial healing formation, so it's called the blastema. That's sort of the new forming arm, and even over just a period of a few days, you can sort of begin to see it growing, and then you can begin to see its segments. So, it's really a fascinating process.

It doesn't necessarily make a lot of sense in a way because it's very energetically expensive to make new body parts. For whatever reason, this group has decided, and this is the way we're gonna evade predators. What's really interesting is this may actually lead to some long-lived properties. In fact, they've found sea urchins that are almost 200 years old.

Are those animals just replacing lost and damaged body parts? How else is the sea cucumber going to live for 200 years? You know, maybe something's happening where tissue deteriorates that can regenerate that tissue. We don't know.