The Immortal Jellyfish
Forever young, occasionally.
Greenland sharks have been documented to live up to 500 years. The giant barrel sponge: over 2,000 years. But the longest-living animal is a tiny sea creature that can seemingly escape death altogether.
The Turritopsis dohrnii has been around since dinosaurs roam the planet! Caveat: not irrefutably proven, as these medusa-like marine creatures have only been studied since the early 1980s.
This tiny jellyfish, however, is capable of living forever by hitting the reset button when it experiences illness, trauma or old age.
An adult Turritopsis dohrnii grows to only 4.5mm and has a bright-red stomach in the middle of its transparent bell. When faced with imminent threat, like say starvation, it transforms back into polyp (think butterfly to caterpillar). The born-again polyp then buds again and grows into an adult, a rare process known as transdifferentiation.
A Japanese scientist, Dr Shin Kubota ran several experiments with these creatures and "resurrected" one of the jellyfish 14 times until the laboratory was hit by a typhoon, which caused rain water to kill the salt-water creatures. Shin concludes that even though the Turritopsis dohrnii is immortal, it is not invincible and is actually kind of fragile. But he believes that the animal can regenerate forever!
If so, why hasn't the immortal jellyfish overpopulated Planet Earth? Because unlike vampires, they can be easily killed by fish, turtles and other jellyfish. Occasionally, they succumb to disease during the polyp stage.
I guess, every living thing has its kryptonite.