The secret of the immortal jellyfish, the longest-lived animal on Earth

Turritopsis nutricula is a tiny jellyfish capable of rejuvenating and sending back its biological clock. Some specimens have been alive for over 60 million years.

The search for immortality has always fascinated scholars, alchemists and philosophers, who over the centuries have tried to discover the secret of eternal life where religion cannot - and perhaps does not want to - arrive. If on a spiritual level it is faith that guides the believers towards an afterlife, science makes of the rigorous observation of nature its modus operandi, to pursue what for many is only a painful chimera.

And yet it is nature itself that provides us with the closest example of true physical immortality. And we are not referring to the giant sponge, capable of surviving up to 2000 years, or the sinuous Greenland sharks, which live to over 500 years: in the animal kingdom, among the most curious creatures that inhabit the depths, there is in fact a tiny being capable of rejuvenating and renewing its life cycle indefinitely.

In particular, it is a small jellyfish known by the scientific name Turritopsis nutricula. And which, not surprisingly, is affectionately called the "immortal jellyfish". While animals such as bees must be preserved even with direct human intervention, this unique hydrozoan of the Oceaniidae knows how to do it all by itself with astounding efficiency, reversing the course of its biological clock when it is injured or is starving. This means that "highlander" jellyfish can potentially live indefinitely.

Although they only have a little more than a few decades of documentation on jellyfish available, scientists believe that there may currently be specimens that have been alive for more than 66 million years. It must be said, however, that due to its small size, Turritopsis can easily be preyed upon by sea killers such as sharks, larger fish and turtles, not to mention this species' pronounced propensity for cannibalism. As a result, it seems rather unlikely that any specimen managed to survive for so long.

In any case, the incredible regeneration process of this jellyfish has a precise biological explanation. However singular. First of all, it is necessary for an adult jellyfish to release eggs and seminal fluid into the water, so as to facilitate their union and subsequent fertilization. When the egg begins to grow it transforms into a small larva called planula that can already swim freely, and that once developed detaches from its root an independent creature capable of feeding and growing independently. Only at the end it reaches the form of adult jellyfish, which goes to mate and reproduce with another specimen.

Unfortunately, however, always in the name of that immoderate research of which we said at the beginning, we are far from any application of these extraordinary regenerative properties in modern medicine. Many of the reasons why we age remain shrouded in mystery: by watching this simple - but not simplistic - animal, we can for now monitor some of its genes and understand how they behave.

Andrea Guerriero