The Turritopsis nutricula is a small, predatory animals with a life cycle in which it reverts to the juvenile form after becoming sexually mature.
Theoretically, this cycle can repeat indefinitely, rendering it biologically immortal. Marine biologists say the jellyfish numbers are rocketing because they need not die.
Turritopsis Nutricula is the only known animal that is capable of reverting completely to its younger self. While most members of the jellyfish family usually die after reproducing, the Turritopsis nutricula has developed the unique ability to return to a polyp state.
Having stumbled upon the font of eternal youth, this tiny creature which is just 5mm long is the focus of many intricate studies by marine biologists and geneticists to see exactly how it manages to literally reverse its aging process. Read more here or here.
On another note, I still think jellyfish should change their names. You see they aren’t really fish. Fish have backbones but jellyfish don’t. It is kind of like starfish (sea stars) – they’re not fish either.