Found in the coastal waters of the Indo-Pacific, Elysia marginata is a small sea slug with arguably the most extreme survival trick in the animal kingdom. When infested with internal parasites, it simply detaches its own head from its body — deliberately — and moves on. The neck wound closes within a day, and the head begins feeding on algae within hours, using stolen chloroplasts — from the algae it eats — stored in its tissue to fuel the regeneration process.

Within around three weeks, an entirely new body has grown — complete with a heart and all vital organs. The discarded body, meanwhile, continues to move and react for days or even months, but is incapable of growing a new head. Some individuals have even been recorded pulling off this trick more than once!