T. dohrnii may bend the rules to rejuvenate itself, but it can't always cheat death. For example, jellyfish, including immortal ones, are prey to other animals, such as fish and turtles. Polyps are ...

the immortal jellyfish is frequently eaten by fish, sea turtles, slugs and other sea creatures — so they are perfectly capable of dying. But even if they do regenerate forever, this begs a ...