The lesson of this week is that we all age. Eventually, though various biological reasons ranging from a breakdown of DNA repair mechanisms to trade-offs that benefit us early in life, our bodies are programmed early on for eventual senescence. However, it would appear that there is at least one species of jellyfish that can live forever.
Turritopsis nutricula isn’t much to behold. It’s only about 4-5mm in length and looks like your typical jellyfish. However, what distinguishes it from other life forms is that it has the ability to undergo complete cellular transformation. If it is on the verge of death (via injury or starvation, for example), it can begin a process called transdifferentiation in which its body breaks down its cells and transforms them into different cell types. If you were to apply this to humans, it would be like the cells in your liver having the capability to transform into nerve cells. After the process is complete, it’s as though jellyfish is as good as new—a younger to boot. It reverts back to its polyp stage and will grow and reproduce from there.
Turritopsis dohrnii, a relative of the immortal jellyfish, also shares aits unique ability to "age backward."
There are limits to immortality, though. Transdifferentiation can only occur after sexual maturation. And presumably, if an adult Turritopsis were to be gobbled up by a predator it would pretty definitively cease to exist. However, this little creature is providing scientists with new opportunities to not only understand the process of aging but also may provide solutions for the kinds of therapies we previously looked to stem cells for.