Sayaka Mitoh and Yoichi Yusa of Nara Women’s University in Japan have observed whole-body regeneration in sea slugs, specifically the species Elysia cf. marginata. The sea slugs pulled their own heads off, discarded their bodies, and eventually regrew a new body from the head!
On close inspection, the researchers found that sea slugs have a slight groove looped on the back of the head region that seems to work as a break-here zone. The bodies left behind can still move on their own for days or even months. An abandoned body, however, doesn’t regrow its head. The leaf-shaped remnant instead turns pale and weak and eventually dies.
Mitoh and Yusa believe that this extreme behavior is a method of getting rid of parasites, although the phrase "throwing out the baby with the bathwater" may occur to you. You can see a video of a slug's head wandering away from its body in the story at ScienceNews. -via Boing Boing
(Image credit: S. Mitoh)