06/08/2026
Life is tough, and some animals react to this by discarding bits of their body. This process is known as autotomy, or ‘self severing’. Crabs, if you’ve ever seen the famous video where one pulls its own arm off, are a famous example.
Lizards are also well known autotomists, patching off their tails as a strategy to escape predation, before slowly regrowing it. However recently a friend of the museum told us about a very special sea slug, Elysia marginata.
To start with, sea slugs are little bit like land slugs, they do roughly similar things in eating plant matter and detritus. But some species can also incorporate plant cells into their body, and in so doing take on the energy creating photosynthetic powers of the plants. These ‘stolen’ plant cells are called ‘kleptoplasts’ and they’re important for what comes next.
Because unlike land slugs, this sea slug can remove its whole body and regrow it!
Researchers Sakaya Mitoh and Yoichi Yusa were studying this slug species and noted a slight ridge around their neck. When the slug was infected with a parasite*, the sea slug completely detached its head from its body.
They left their internal organs behind and after sealing the wound began the process of regrowth. Having discarded their stomachs, they couldn’t eat, and so the suggestion is that the chloroplasts ingested by eating algae gave them a photosynthesising back-up battery powerful enough to jumpstart recovery.
This form of extreme autotomy differs from lizards and crabs, which just get rid of a bit of themselves, usually a sticky-outy appendage. It also happens relatively slowly, implying that it isn’t about direct, violent predation, but a reaction to more sluggish changes.
Anyway, we thought that was worth sharing with you…
*the sea slugs also reacted with autotomy when a thread was tied around their neck and within a day most had shed their body. The parasite in question was a copepod, a type of crustacean, lol
P.C: Mitoh, Yusa, 2021
