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How to Grow a New Body from an Old Head? Ask a Sea Slug

Team StoryWeavers|June 06, 2022, 17:40 IST| 1

how sea slugs regrow

Regeneration is a very common ability within the animal kingdom. If extending life expectancy is on your mind, you simply can’t overlook the option of regrowing tissue – a feat we humans are sadly less capable of doing (except for a certain organ!)

Arm fall of boy

Image Source: Reddit

You must have seen how easily a lizard can let go of its squirming tail to escape if trapped or a cockroach that can still crawl with half of its legs gone! Over the years, they have invariably earned the titles of the ‘undefeated ones’ – as they can easily regrow parts of their body and survive. But these two kinds of rippling, green-tinged sea slugs have taken it to the extreme.

Superpowered Slugs

Meet the two species of sacoglossan sea slugElysia cf. marginata and E. atroviridis – that have the superpower to regrow an entire new body from neck down with a fully functional heart and other body parts, just from its old head!

Sea Slug Source:


Yes! You read that right. It is not even a reproductive tactic – the discarded old body eventually dies while the sea slug continues to live and grow on with its new body. They decapitate themselves from their old bodies and just keep crawling until the new body takes its full shape, biologists Sayaka Mitoh and Yoichi Yusa of Nara Women’s University in Japan, found.

The discovery was a matter of pure serendipity!

According to the biologists, they discovered this unusual nature of these sacoglossan sea slugs just by luck! They were studying these slugs in their lab, when one day, they noticed that one of these slugs had randomly autotomized; that is, dropped off its body, like how a lizard drops off its tail. “Except, it wasn’t just a tail, the entire body was pulled free from its head and the head was moving around on its own,” reported Sayaka Mitoh. “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 within days.”

Within a few hours of autotomy, the heads of young slugs started feeding. The heart started regenerating within a week - and within just three weeks, the sea slug had a whole new body, good as new. Image Source: S. Mitoh and Y. Yusa/Current Biology 2021

Within a few hours of autotomy, the heads of young slugs started feeding. The heart started regenerating within a week – and within just three weeks, the sea slug had a whole new body, good as new. Image Source: S. Mitoh and Y. Yusa/Current Biology 2021

Why do these slugs shed their heads off?

The reason is not clear. Perhaps this helps rid the slugs of pesky parasites that hinder their reproduction, believes the biologists. The detached bodies could also give these slugs a drastic but effective way of dealing with parasites. In one such test, the Japanese researchers found that few of these slugs that ditched their bodies were parasitised by copepods (parasitic crustaceans, found in nearly every freshwater and saltwater habitat).

READ MORE: Why are Australians harvesting mosquitoes?

If you think a dramatic ‘whole body’ regeneration is such a slug thing, hold on! Slugs are NOT alone when it comes to regenerating body parts! There are many reptiles and amphibians that exhibit remarkable tissue regeneration. Read on and see how many of them you already know.

How Lizards regenerate their cut tail

The most common reptiles that often visit our house and stay rent free, the lizards are masters in shedding their legs off to escape a predator’s claws. They take the term ‘fight or flight’ to a whole new level. When pulled by predators, lizards shed their tails in response. Their wagging tail can distract a predator for up to 30 mins, enough time for the lizard to escape!

Starfish or Sea Stars and their regrowing tales

Everybody loves these five-limbed creatures who have the ability to regenerate their limbs and at times their whole body! Even if they are down to just one arm, as long as its central nerve ring is intact, Starfish (Sea Stars) can regenerate easily. Interestingly, their shed arms at times can grow into a new starfish.

Facts about starfish

regeneration of body parts

Yes! Axolotls are for real and look this cute! But their fame doesn’t confines to their looks alone. Axolotls have a remarkable ability to make copies of itself like a xerox machine. Unlike starfish or other animals, axolotls don’t heal large wounds with the fibrous tissue that composes scars. Instead, they just regrow their injured parts. From regenerating a missing limb, tail, eyes, and parts of their brain, heart, and lower jaw, axolotls are no wonder one of the favourite study subjects among scientists.

regeneration of body organs

Well, you might be surprised to see humans on this list. While we are not champions when it comes to regenerating missing parts like other mammals or reptiles, we certainly can regenerate one body organ to some extent – the liver. While with most other organs like the heart, the damaged tissue is replaced with scar, like on the skin. However, the liver is able to replace its damaged tissues with new cells. Speaking of human organs did you know that scientists recently discovered a new organ in our body? It is called the Tubarial salivary glands.

Hope this article was helpful? Do you know any other species that can regrow its body parts? Do tell us in the comments section.

About the Author

Books are Tanaya Goswami’s first love and cheesecakes come a close second. Talking about movies, music, calligraphy, politics, and Elon Musk will get you listed under the friends’ section of her diary. Ever since moving on from her job as an English lecturer, she spends her time at BYJU’S crafting stories filled with emotion and sprinkled with sarcasm. Outside of work, she’s either learning something new (French, most recently!) or is curled up with a book and a cup of coffee. She firmly believes that discovering what you don’t know is the key to knowledge and is constantly working towards improving herself. Drop in a line at if you liked her stories, have something nice to say, or if you have compelling ideas to share!

Leave a Comment



Sunandana Kar

April 28, 2021

They look icky??
By the way , the human part is the best ❤️


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