Warning: some sea slugs develop new bodies after beheading

TOKYO (AP) – Scientists have discovered the ultimate case of regeneration: Certain decapitated sea slugs can regrow hearts and whole new bodies.

This “natural wonder”, reported Monday in a biology journal, could eventually help scientists better understand and fight against the regeneration of human tissue.

Biology researcher Sayaka Mitoh said she loves studying Japanese sea slugs because they are small, cute and weird. They can even briefly photosynthesize like a plant getting its food from the sun.

One day in the laboratory, she saw something strange: a sea slug had beheaded and the head was still moving and living. Then a few others did the same, according to a study by Current Biology.

So, Nara Women’s University doctoral student and aquatic ecology professor Yoichi Yusa tried herself, chopping off the heads of 16 sea slugs. Six of the creatures began regeneration, three succeeding and surviving. One of the three even lost and regained his body twice. Two different species of Japanese sea slugs did this regeneration trick.

Other creatures can reject body parts when needed, such as when some lizards let go of their tails to get away from a predator, in a biological phenomenon called autotomy.

“We believe this is the most extreme case of autotomy,” Yusa said. “Some animals can autotomize their legs, appendages or tails, but no other animal loses its entire body.”

Scientists believed that such a relatively large animal – one of the species of sea slugs can grow up to 6 inches long – couldn’t survive without a heart to pump blood and nutrients to the brain, the marine biologist said. Canadian Susan Anthony, who was not. part of the study.

But the same thing that makes this species spectacular is probably what helps it pull off the trick, Anthony and Yusa said.

When these sea slugs eat a certain type of algae, they can photosynthesize their food from sunlight and oxygen, just like a plant, for about 10 days, Yusa said. What probably happens after the beheading is the head acts like a plant, he said. It turns green and gets its energy from oxygen and sunlight. The fact that it gets tiny helps, he says.

These species likely developed the feat as a means of controlling pests, Mitoh and Yusa said.

Humans may be able to learn something useful from sea creatures, several scientists have said. What’s particularly intriguing is that these sea slugs are more complex than tapeworms or other species known to regenerate, said Nicholas Curtis, professor of biology at Ave Maria University who was not part of the of the study.

“It’s of course a natural wonder, but understanding the underlying molecular mechanisms involved could help us understand how our cells and tissues can be used to repair damage,” Curtis said in an email.

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