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Scientists Discover Sea Slug That Can Regenerate Body After Being Decapitated

SCOTT SIMON, HOST:

Look; we've all heard of extreme makeovers, but slugs take that idea to new levels. Sakaya (ph) Mitoh, a researcher in Japan, discovered a slug in a lab a few years ago that was somehow separated from its head, but that head still moved around almost as normal. The body also squirmed around, as slugs do, with a beating heart and every other slug organ. Sakaya Mitoh watched as the slugs began to grow whole new bodies - no workouts, no tedious keto diet. The findings were published this week in Current Biology, and that caught the attention of Susan Milius.

SUSAN MILIUS: It kind of resonated with me because - I may be the only person on Earth this is true for, but there have been times when I have looked in the mirror and thought, you know, from the neck down, let's just start over, can't we?

SIMON: She's written about sea slugs for Science News. So how does this regeneration process start?

MILIUS: Well, it takes them a couple of hours. And they just sort of tear their heads away from their bodies. And then the head crawls around on its own, even though the bodies have the hearts in them. And the hearts are still beating.

SIMON: Sounds like a rough process, I got to say. The head can survive weeks without its body. We can't survive even one week without BJ Leiderman, who writes our theme. The slug body remains active for a little while, looking like a little green leaf just wafting around. But it is doomed to die.

MILIUS: The bodies can't regenerate a head. But the head, which is only 20% or so of the animal, can regrow a whole, much bigger body.

SIMON: That includes regrowing the heart, the kidneys, intestines, everything that goes into a slug.

MILIUS: It's a big thing if you're a little, tiny sea slug. But they manage to do it.

SIMON: How do these slugs survive without any organs? Well, scientists venture the guess that it's because the slugs are what they call kleptoplasts. They steal chloroplasts from the algae that they eat, and that's how they can survive from energy that's drawn from the sun.

Now, why would a sea slug voluntarily divest itself of its entire body? Shedding a body part and regrowing it happens in nature on a small scale with limbs, though humans shouldn't try it at home. But with these slugs, researchers believe there's another cause.

MILIUS: The slugs can get terrible parasites. The parasites take over their reproductive system, so the slugs themselves can't really reproduce. And the parasites use a lot of energy. So basically, the sea slug is reproductively pretty much dead.

SIMON: So when they realize their bodies might be just too parasitic for reproduction, the slugs shed them and grow new bodies, parasite-free. Whatever the actual cause, Susan Milius thinks the marvelously complex sea slug has spent just too long out of the biological spotlight.

MILIUS: Some of them are sort of tasteful, you know, gray T-shirt, black jeans kind of organisms. And some of them are glitter, glam, Mardi Gras, outrageous stuff. They're purple. They have pink hair. They have frills and frippery. They are just outrageous. And they need a better name than sea slug.

SIMON: What about sea celebrities, the ultimate makeover artists?

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.