The Planet's Only Immortal Animal

A species of jellyfish has evolved the potential for immortality - and they're starting to spread.
The species turritopsis nutricula is able to transform itself from its mature state back into a polyp (immature jellyfish) and then back again.The species, which is only 4-5 mm in diameter, performs this miraculous feat using a process known as transdifferentiation, in which one type of cell transforms into another. While this sounds a lot like what happens in stem cells, the process is distinct.

Turritopsis nutricula isn't the only species to use the technique; salamanders use the process to regrow limbs, while chickens utilize it to repair damaged eyes. Turritopsis nutricula, however, is the only species able to regenerate its entire body. The entire transformation from adult to polyp takes place very rapidly, helping to explain why it has never been observed in the wild. The process, however, has been observed in the lab, and so far 100 per cent of specimens have been capable of the transformation.

Theoretically, the process can go on indefinitely, which may help to explain why scientists have noticed a spike in the number of these jellyfish in the oceans. "We are looking at a worldwide silent invasion," said Dr Maria Miglietta of the Smithsonian Tropical Marine Institute.
The jellyfish are believed to have originated in the Caribbean, but, due to the common shipping practice of emptying ballast water in foreign ports, is now found all over the globe.
While the jellyfish can potentially live forever, it's unlikely that one ever will.
That's because like other jellyfish, Turritopsis nutricula is often eaten by other animals and readily succumbs to disease.

Other larger long-lived species have a better chance at reaching impressive ages. Bowhead whales, tortoises and koi fish can all live to be more than 200 years old. Plant species can live even longer. The oldest known bristlecone pine tree is nearly 5,000 years old.
That isn't stopping scientists around the globe from searching for the secret that allows this unique jellyfish to reverse the aging process.
Mastering transdifferentiation could be the key to discovering a real fountain of youth....and when we do that, we could live, if not forever, at least a very, very long time; enough time to do over all those things we did badly the first time.