These Sea Slugs Behead Themselves And Grow A New Body In Less Than A Month

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The head and body of the Elysia marginata a day after the decapitation. The slug's body is over 80 percent of its total weight (Credit: Sayaka Mitoh)

Regeneration, or the ability to regrow body parts, is a fairly widespread phenomenon in the animal kingdom. However, the skill is usually restricted to growing a new tail or a new limb. Now, researchers have found two species of sacoglossan sea slugs — Elysia atroviridis and Elysia marginata — that deliberately detach their heads from their original bodies and grow brand new ones!

Biologists Sayaka Mitoh and Yoichi Yusa, from Nara Women’s University in Japan, stumbled upon the slugs' talent while observing the creatures in their laboratory. "One day, I found an individual of Elysia marginata with its head and its body separated," Mitoh said. "I thought the poor slug would die soon."

To her astonishment, the wound at the back of the slug's head healed rapidly, and within days there were signs of a new body being generated. In just three short weeks, the slug managed to replicate 80 percent of its original body, complete with vital organs. "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,” Mitoh told Live Science.

Once detached, the sea slug's head continued to live and starts to generate a new body within days (Credit: Sayaka Mitoh)

Though the slug's original body also continued to wriggle around for a few days, and in some cases even months, after being detached, it eventually withered and died. Mitoh said, “The bodies gradually shrank and became pale, apparently from losing chloroplasts, and eventually decomposed. The beating of the heart was visible just before the body decomposed.”

The scientists are not sure why the creatures discard their bodies. They speculate it could be to rid themselves of internal parasites. It could also be a clever technique to escape from predators. However, only the younger slugs could grow new bodies. Though the heads of the older slugs survived for up to ten days they did not grow and eventually died. The number of times the slugs can pull off this amazing trick is believed to be restricted. While one individual in the laboratory tank managed to do it twice, Mitoh and her team think that may be the limit.

The slug steals chloroplasts from algae and uses them to photosynthesize and generate (Credit: Sayaka Mitoh)

Regrowing cells requires a lot of energy and is usually impossible without nutrition from the body. However, the slugs have found a clever way to get around this issue. They steal chloroplasts — the portion of a cell that enables plants to convert sunlight into energy — from the algae they consume and photosynthesize it in their own tissues.

The researchers, who published their findings in the journal Current Biology on March 8, 2021, plan to continue studying these exciting gastropods. "Sacoglossan sea slugs are well known for their ability for kleptoplasty [stealing cloroplasts] and we now learned that they have another great ability," Mitoh says. "We are very interested in these small animals."

Resources: Livescience.com. ScientificAmerican.com,

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188 Comments
  • maxride1456
    maxride1456Thursday, May 13, 2021 at 3:10 pm
    eww but so cool and weird
    • alphadog
      alphadogThursday, May 13, 2021 at 12:58 pm
      it is really really weird😨
      • hhdfhdhf
        hhdfhdhfWednesday, May 12, 2021 at 12:28 pm
        WOW! SO COOL!!!!!!!!
        • hjjj
          hjjjWednesday, May 12, 2021 at 7:16 am
          odd but amazing!!😝🤯
          • cloudycrystal
            cloudycrystalTuesday, May 11, 2021 at 7:22 pm
            I wonder how old the slugs can live...?
            • cloudycrystal
              cloudycrystalTuesday, May 11, 2021 at 7:19 pm
              Very Cool!!!!! I will use this for my assignment!!!
              • uniman10
                uniman10Tuesday, May 11, 2021 at 8:11 am
                cool!
                • cazuhely-161003051200
                  cazuhely-161003051200Monday, May 10, 2021 at 10:45 am
                  Cool! But, kinda creepy also... it can distech it's head from it's body! How freaky is that? But, that's really cool! I wonder how it re-grows internal organs though.
                  • lemondemoncore
                    lemondemoncoreMonday, May 10, 2021 at 9:41 am
                    this is cool
                    • grogu
                      groguMonday, May 10, 2021 at 9:36 am
                      That's kind of creepy but cool