In a stunning video, the Decapitated head of a young sea slug can be seen pulling itself from its body and crawling, all while growing a new body.

Elysia Marginata Sea Slug

The Elysia Marginata that has been trending among science enthusiasts and experts are a highly variable species with both sedentary and migratory forms. It's easily recognizable with its bright green color and continuous black marginal line.

The sea slug is endemic to Indo-Pacific waters such as the Philippines, Hawaii, and more.

Wonders of the Sea Slug's Decapitated Head

A study published in the journal Current Biology entitled, "Extreme Autonomy and Whole-Body Regeneration in Photosynthetic Sea Slugs", reports how an Elysia cf. marginata's decapitated ehad was able to pull itself free of the original body, crawl around, and grow an entirely new body according to ecologists from Nara women's University, Japan.

Within hours, the separated head was seen nibbling on algae again reports Yoichi Yusa and Sayaka Mitoh, co-authors of the study. After just 20 days, the head had sprung a third of its body back, heart and all.

This is the first instance of a sea slug dramatically regenerating its whole body, says Yusa.

Yusa explains that many creatures are known to regenerate. Including planarians, cross-eyed flatworms used to study regeneration in biology students, that are better at the process. These worms are able to regenerate their whole body from multiple pieces yet, they are unable to regrow their hearts.

Ascidians, a group of tubelike sea squirts, are considered the most complex regenerators capable of whole-body regenerations. Yet, these creatures are only able to regenerate simple bodies with no hearts.

Vertebrate regenerators like salamanders that regrow their tails left in the jaws of predators are unable to regrow their whole body from decapitated heads.

Elysia marginata
(Photo : Rickard Zerpe / Wikimedia Commons)

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Understanding the Sea Slugs Regeneration

Mitoh was the first to notice the sea slugs' regeneration by chance in Elysia slugs kept in the lab.

Which species of Elysia can turn into crawling heads is still a mystery. Sonia Cruz, a marine biologist at the University of Aveiro, Portugal working with two other Eylsia species has been unable to record the same regeneration. Although, she cautions that she has not been able to do systematic tests.

Ecologists Mitoh and Yusa explain that the sea slugs' head takes several hours before it can rip itself completely loose from its body, which indicates that the de-heading isn't helpful during predatory attacks.

Instead, researchers suggest that the decapitated head gives sea slug a drastic and effective way of dealing with parasites.

A batch of E. atroviridis sea slugs caught in the wild, some de-headed slugs' original bodies were parasitized by copepods.

Close inspection by the team found that sea slugs had a slight groove looped on the back of their head regions that worked as a break-here zone. Bodies left were still able to move on their own for days or months. After, the remnant turns pale and dies off on its own.

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