How does the Greenland shark live so long?

The Greenland shark is the longest-living vertebrate in the world.With a prehistoric appearance, it has lived in deep waters for over 300 years.

Elongated shape, gibbous body, prehistoric traits.The shark of Greenland – the scientific name of the species is Somniosus microcephalus – has rightly won the title of longest-lived vertebrate in the world:in fact, it boasts an estimated lifespan of well four hundred years.And now, finally, thanks to an international study, we also know how he lives so long.

Who is the Greenland shark

But let's take a step back.An elderly individual swimming today in the icy waters ofNorth Atlantic he might have been born when Napoleon Bonaparte began to govern in France, in 1799, or even while the plague epidemic of 1630, so dear to him, was raging in northern Italy. Alessandro Manzoni.

Representatives of this species, so rare and still little known, they don't meet often.The only observations of behavior we have come from video carried out at about two hundred meters deep, which shows well how much they are slow in movement.Understandable, considering the venerable age.This was demonstrated by a study published in Science in 2016, in which a research group led by John Stiffensen of the University of Copenhagen had discovered, thanks to radiocarbon dating, that some females, which accidentally ended up in the nets of fishing boats, had an estimated age of around 272 years.From the analyses, it also emerged that females reach sexual maturity when they exceed four meters in length, i.e. with a minimum age of 156 years.

Why Greenland sharks live so long

Despite scientific efforts, however, the molecular mechanism that allows this species to achieve such impressive ages had still remained unknown. Until now.The species' elixir of life was just revealed by a search coordinated by Arne Sahm of the Fritz Lipmann Institute on Aging (Fli) in Jena, Germany, carried out with colleagues from the University of Copenhagen, the Biophysics Institute of the CNR and the Scuola Normale Superiore of Pisa.

Experts have the entire genome of the Greenland shark has been mapped for the first time, discovering that its DNA is twice as long as that of humans.The sequencing operation was quite complex:in fact, with 6.5 billion base pairs, its genetic code is the largest of all the shark genome sequences known to date.And it wasn't the only finding of the study.

Over 70 percent of the genome contains repeated and often self-replicating elements, also called “selfish” because they do not carry functional information.Typically they can destroy the integrity of essential genes and reduce the overall stability of the genome, but in the Greenland shark they could be the keystone of longevity.In fact, during replication (the biological process of producing two replicas of a DNA molecule identical to the original) these can "sequester" functionally more relevant genes, which are then in turn copied.Not only that.

Studying DNA

The physiology of organisms works like a perfect car, so much so that these evolutionary "doubles" are not at all useless, as one might think, on the contrary.They seem to be involved in the "repair" of DNA damage, the random "errors" that occur in our cells thousands of times every day.This is not a surprising fact, because various comparative genomic studies had already revealed how the species of mammals particularly long-lived are also exceptionally efficient in repairing their DNA.And it is precisely the presence of these genetic duplicates that could explain the longevity of this and many other species on Earth.

What's more, in the shark's DNA Somniosus was also identified a specific alteration in the p53 protein, also known as the “guardian of the genome,” which coordinates the response to DNA damage in humans and many other species, a checkpoint for the development of tumors.

In short, this species of shark with a prehistoric appearance, which lives where there are no predators And hunt thanks to bioluminescent parasites that stick to his cornea, is undoubtedly well equipped to resist the elements and the passing of centuries.And, like her, some others could benefit from the same evolutionary tools.Just think of other long-lived vertebrates, such as the African tortoise Centrochelys sulcata, with an average lifespan of 344, or the “neighbor” Balaena mysticetus, the Greenland right whale, which could live about two hundred years.

The new research was published as a preprint in the magazine BioRxiv, the online archive dedicated to sharing scientific data and results in the phase prior to official publication in one of the prestigious peer-reviewed journals.In this specific case, the genome sequence and the corresponding web resources provided by the team of experts will allow researchers from all over the world to analyze the genes of their interest in the DNA of the Greenland shark. Because science, after all, is done all together.