Don’t lose your head! Unless you’re a sea slug.

Researchers discover two species of sea slug that can literally remove their heads and grow new bodies
sea slug "Nobody panic! This is totally normal!" A sea slug head and its former body. (Sayaka Mitoh)

Heads are pretty important for most animals. You've got the eyes, nose, ears, mouth. The brain. Lots of crucial stuff in there for living life to the fullest.

But not if you're a certain type of sea slug!

Researchers in Japan have discovered that not one, but two species of sea slug are capable of removing their own heads. Then, the new head grows an entirely new body from the neck down, in just a few weeks. And, the original body that was discarded? It can live for days, weeks, even months after the event.

A-head of the game

A more complete sacoglossan sea slug. (Sayaka Mitoh)

It's an incredible ability that these animals (a pair of species of sacoglossan sea slugs) have. And scientists happened upon it completely by accident.

Sayaka Mitoh, a doctoral student at Nara Women's University in Japan, was merely observing the animals in a tank when she noticed that one of them had removed its own head! And the head was still moving and living. This led to a series of tests that proved that this was not an unusual circumstance. This type of body regeneration was a relatively normal for these animals.

Of course, there are various reptiles, amphibians, sea stars, and worms that can drop tails or limbs and completely regrow them. But by losing its head, this sea slug finds itself in a very unique category.

How and why?

Exactly why they have this ability will require more study. So far, the scientists theorize that it could be to either escape a predator's attack (sacrifice their body as a meal while their head escapes), or to get rid of parasites that have infested the body.

But even more intriguing to answer is the 'how'. How do these animals survive self-decapitation?

So far, scientists believe that it has to do with their ability to photosynthesize (make food from sunlight) just as plants do. This is something that they get from the algae that they eat. Clever, clever, sea slugs! As for the regeneration, that's a trickier question. But scientists are hopeful that the answer might help them learn how to successfully grow human cells in a lab—a key to the future of fighting disease and infection.

While we wait for the answer to these questions, please enjoy this video from Live Science of the incredible, head-removing, new-body-growing sea slug.

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