# Sacoglossan sea slugs shed the whole body with the heart and regrow it from the head

- Published: 2026-11-08 19:20 UTC
- Section: Life & Health › Biology & biochemistry
- Tags: sea slug autotomy, Elysia regeneration, body regeneration, kleptoplasty, sacoglossan sea slugs, chloroplasts in animal cells, Nara Women's University, Mitoh and Yusa
- URL: https://realtech.media/news/rt-b222e8d05d6304ca860c6592_sacoglossan_sea_slugs/

**Researchers at Nara Women's University described two sea slug species that shed the body and regenerate a new one, heart included. The shed body does not regrow a head.**

![Sacoglossan sea slugs shed the whole body with the heart and regrow it from the head](https://realtech.media/media/2026/11/3a99aa6aea8e99ad.jpg)
*Nhobgood (talk) Nick Hobgood, Wikimedia Commons, CC BY-SA 3.0*

In March 2021, Sayaka Mitoh and Yoichi Yusa of Nara Women's University reported in Current Biology that two species of sacoglossan sea slugs, of the genus Elysia, can shed the main body, including the whole heart, and regenerate a new one [1]. Autotomy, the voluntary shedding of a body part, is known in arthropods, gastropods, starfish, amphibians and lizards. In those animals, as a rule, only terminal parts such as appendages or tails are regrown [1].

## How the slug sheds and rebuilds its body

The separation happens at the neck, where a thin groove marks a line of rupture. The animal tightens its tissues there, and complete separation takes several hours, with no visible bleeding or agitation. The head is left with roughly 20% of the original weight: the rest, about 80%, including the heart, intestine and reproductive organs, stays behind. In the laboratory, the researchers triggered the separation by looping a thread around the groove.

The head returns to grazing on algae within hours, and the wound closes in under a day. Only young individuals coped with the procedure; older ones did not survive. Regeneration follows a fixed order, heart first and then the remaining organs. After a week the regrowth is already visible, and about a third of the young slugs had a complete body again in roughly twenty days.

The shed body fares worse. Without a head it keeps moving for days, sometimes months, and still responds to touch, but it does not regenerate a head [1]. It gradually turns pale, weakens and dies.

## Chloroplasts and the possible purpose

Sacoglossans take up chloroplasts from the algae they eat and keep them in their cells for photosynthesis, a process called kleptoplasty [1]. The authors propose that this trait may help the animal survive autotomy and regenerate [1]. The head has no digestive tract to draw on during rebuilding, so photosynthesis could serve as an energy source.

Why the slugs do this is still open. Escaping a predator seems unlikely, since the process is too slow to shake off an attacker. The researchers lean toward removal of parasites: slugs infested with small crustaceans were the ones that shed the body, as well as those that shed only part of it. The team is now looking for the stem cells involved in regeneration.

## Sources

1. [Current Biology](https://doi.org/10.1016/j.cub.2021.01.014)
2. [science-et-vie.com](https://www.science-et-vie.com/nature-et-environnement/animaux/en-2021-des-chercheurs-ont-decrit-une-limace-de-mer-capable-de-se-separer-de-son-corps-sa-tete-pouvait-en-reconstruire-un-coeur-compris-en-une-vingtaine-de-jours-265158.html)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-b222e8d05d6304ca860c6592_sacoglossan_sea_slugs/