The Immortal Jellyfish

One of the most diverse animal species in our oceans are jellyfish, which have over 200 subspecies, each with its own distinctive characteristics and habitat-based adaptations. Despite their frequently vibrant and cheerful appearance, some jellyfish species are actually highly poisonous.

However, one species of jellyfish boasts a talent not shared by any other form of life, not even other jellyfish. The only known organism that has the ability to regenerate its cells to their newborn state is the jellyfish species Turritopsis dohrnii, which was originally discovered in the warmer seas of the Caribbean and Mediterranean. The process is completely automatic and only starts when there is a serious emergency, such as extreme famine or injury.

Although we still don't understand how Turritopsis dohrnii acquired this capacity, it is the only physiologically immortal animal we are aware of (as opposed to being "really immortal," as they may still be eaten by predators and die). Its cells appear to be fully capable of repairing - and even undoing - the harm accrued over time, which is what causes the rest of us to get old and pass away.