These sea slugs cut off their heads and grow a whole new body

Most animals cannot lose their bodies and survive. Two species of sacoglossal sea slugs are not most animals. A team of researchers observed sea slugs cutting off their heads and then replenishing their bodies with hearts and other internal organs. The act of losing part of the body is called autotomy. It is what do lizards do when they lose a tail for self-preservation.

Dropping an entire body is much more dramatic than losing a tail. “We thought he would soon die without a heart and other important organs, but we were again surprised to find that he regenerated the whole body,” Sayaka Mitoh of Nara Women’s University in Japan said on Monday in a Cell Press release. Mitoh is the lead author of a study on sea slugs published in the journal Current Biology of Cell Press.

Regenerating sea slugs were younger individuals. It took about a week to regrow the heart and they had completely regenerated their bodies within three weeks. Researchers suggest that there may be “stem cells” where the neck cuts off, allowing regrowth.

The young sea slug heads were able to move around and feed on algae shortly after separation, which appears to have been key to their survival. Older slug heads did not feed.

Unusual animals are inspired by plants. “The sea slugs in question were already unique in that they incorporate algal chloroplasts that they eat into their own bodies, a habit known as kleptoplasty,” Cell Press said. “It gives animals the ability to fuel their bodies through photosynthesis.”

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The ability to regrow a body is not unknown. Some species of jellyfish can regenerate after an injury. The self-decapitation part of the sea slug process adds to the mystery, however. Researchers suggest that the action may be a way to get rid of internal parasites, but the impetus is unclear.

The surprising process of body regeneration is already giving scientists ideas for new studies. Mitoh said, “Since the shed body is often active for months on end, we may be able to study the mechanism and functions of kleptoplasty using living organs, tissues or even cells.”