Self-decapitating sea slugs cut off their own heads, then regenerate brand-new bodies

Story Highlights

  • Some sea slugs can regrow hearts and whole new bodies, even after removing their own heads.
  • "We were surprised to see the head moving just after it was severed."
  • Humans may be able to learn something useful from the sea creatures.

Amazingly, some animals can survive decapitation, according to a new study.

Researchers discovered that two species of Japanese sea slugs can regrow hearts and whole new bodies, even after removing their own heads.

This could eventually help scientists better understand and tackle regeneration of human tissue.

The slug’s head, separated from the heart and body, moved on its own immediately after the separation, the study shows. Within days, the wound at the back of the head closed. The heads of relatively young slugs started to feed on algae within hours. 

They then started regeneration of the heart within a week. Within about three weeks, regeneration was complete.

“We were surprised to see the head moving just after (it was severed),” said study lead author Sayaka Mitoh of Nara Women’s University in Japan. “We thought that it would die soon without a heart and other important organs, but we were surprised again to find that it regenerated the whole body.”

WATCH THE VIDEO: See the head and the body of a sea slug move spontaneously, 3 days after separation. 

Then Mitoh and aquatic ecology professor Yoichi Yusa tried it themselves, cutting the heads off 16 sea slugs. Six of the creatures started regeneration, and three succeeded and survived. One of the three even lost and regrew its body twice. 

Other animals can cast off body parts when needed, such as when some lizards drop their tails to get away from a predator, in a biological phenomenon called autotomy.

Mitoh isn’t sure how the sea slugs manage the regeneration. But, she suspects there must be stem-like cells at the cut end of the neck that are capable of regenerating the body. 

It’s also unclear why the slugs are doing this. One possibility is that it helps to remove internal parasites that inhibit their reproduction. Researchers also don’t know what immediate cue prompts the creatures to cast off the rest of the body. These are areas for future study.

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

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

The study was published Monday in the journal Current Biology. 

Contributing: The Associated Press

The head and the body of a Japanese sea slug, a day after the head was removed. (Photo: Sayaka Mitoh)

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