Solar-Powered Sea Slugs Grow New Bodies By Removing Their Own Heads
A new study out of Japan has revealed that certain sea slugs, which are partially 'solar-powered,' can intentionally remove their own heads in order to grow a new body. The strange discovery was made after one researcher discovered that a sea slug specimen kept in the lab was headless — and that the head was moving around on its own and eating algae.
The unique sea slug decapitation discovery was made by Sayaka Mitoh, who recently detailed the work for The New York Times. Mitoh was a Nara Women's University Ph.D. candidate at the time she discovered the headless sea slug amid her lab's specimens. Upon examining the slug, Mitoh found that the head was not only still living but also moving around and eating.
The head was seemingly removed via a process called autotomy, which in this case means the sea slug decapitated itself by dissolving its neck tissues, then tearing its head free. This was the first time an animal had been found to remove its own head in order to ditch its old body — and then grow an entirely new body to replace it.
Though mysteries about how the Elysia marginata sea slugs pull off this process, and for what purposes, remain a mystery, the researchers found evidence that the self-decapitation was a method for getting rid of parasites. The old discarded bodies were found to have parasites, while the newly grown bodies were parasite-free.
Multiple sea slugs were observed to decapitate themselves during the study, including one that performed the head removal twice, but not all of the slugs shed their old bodies during their lives. The old bodies, despite lacking a head, were found to still react to stimuli for up to multiple months.
The new bodies, meanwhile, took up to around three weeks to regrow — and, the researchers note, these slugs' ability to partially sustain themselves using photosynthesis may explain how the free-roaming heads survived long enough to grow new bodies. The full study can be found in the journal Current Biology.