This creature knows more than one way to grow back its head

Researchers have analyzed changes in gene expression during regeneration: growing back its head is not a problem for this creature

That animals are able to change their appearance is well known: snakes molt, chameleons change color, in many mammals in the transition from infancy to adulthood change their teeth. Yet there is a microscopic animal that can regrow entire parts of the body, including the head: the Hydra.

What is the Hydra

If you know a little mythology, you imagine the Hydra as a huge, nine-headed poisonous sea snake.

In reality, it is a microscopic, tube-shaped eukaryote. It is up to 10 millimeters long and lives in rivers around the world. It is a carnivore, which paralyzes and captures its prey thanks to the forest of tentacles on its body. It then takes them to its mouth, which also serves as an anus. It feeds, as you can imagine, mainly on insects and small crustaceans. It is not the only very small but very dangerous aquatic predator.

But its peculiarity is that it can regrow entire body parts, even the head, from a small piece of tissue or a handful of cells.

"It's one of those creatures that you think can't die, except by killing or starving them," says Ali Mortazavi, a biologist at the University of California who has long studied the Hydra. In fact, it seems there really is such a thing as an immortal animal.

The ability to regrow body parts

In addition to the more easily imagined benefits of growing back body parts, the Hydra uses this ability to keep itself from succumbing to aging or disease. It would be very interesting for us to replace our eyes as we lose sight with age: if the Hydra had eyes, it could do so.

But how does the Hydra regenerate body parts? To figure that out, the researchers analyzed changes in gene expression during head regeneration: and so they discovered changes in the regulation of parts of Hydra's DNA, called enhancers. These elements help the formation of many genes, including those that regulate regeneration.

Something that doesn't happen, for example, when Hydra reproduces, asexually creating a copy of itself. In this case, the creation of gene expression is extremely slow.

A very important discovery for understanding how the nervous system formed in animals and humans, and one that could provide useful tools for regenerative medicine.