The surprising longevity lessons from the world’s oldest animal

You could be forgiven if you haven't heard of the ocean quahog, also known as the Icelandic cyprin: it's not a species that gets a lot of attention on television. It is a large bivalve mollusk found in the sand on both Atlantic coasts, from southern Florida and Cadiz in Spain to the colder waters of Quebec in Canada and Norway. If you've tried clam chowder in the US, you've almost certainly eaten it. Its shell has fine lines reminiscent of the rings of a tree trunk, and like tree rings, these lines can be used to determine age.

Researchers named the oldest known specimen Hafrun, an Icelandic name that means “mystery of the ocean.” Hafrun was born in 1499 and lived as his ancestors had lived for generations, quietly eating a frugal diet gathered off the coast of Iceland. In this sense, his life was unremarkable, if not for the fact that it went on and on and on. In fact, it only ended in 2006, when it was pulled from the sea by a team from the University of Exeter in the UK. Sclerochronologist Paul Butler the researcher was tasked with aging him. Sclerochronology involves the analysis of bivalve shells to construct a time frame for their environment.

“It was originally estimated to be just over 400 years old, but a closer look at the growth lines and comparisons with other shells revealed that it was actually 507 years old,” he tells me. It is likely that even older individuals exist, especially in the cold waters around Iceland where they grow more slowly and live even longer. Is there an upper limit to their age? “It's hard to believe they live much longer,” says Butler, “though we once got the ages of a few people analyzed by a mathematician who said they could, in principle, live forever.” Well, that's mathematicians for you.

The key to a quahog's longevity appears to lie in its mitochondria, the structures in our cells that use food to provide us with energy. By “us” I mean us eukaryotes – all of us complex organismsfrom yew trees and mealworms to jellyfish and rabbits.

“The presence of robust mitochondria, which Arctica islandica possesses, is of paramount importance for healthy aging in a wide variety of model species,” says Enrique Rodriguez, who researches mitochondria at University College London.

Quahog's mitochondria are literally tougher. Their membrane is more resistant to damage than other species. The mitochondrial membrane is filled with protein machinery that processes electrons and protons and generates ATP, a versatile energy molecule used in cells. In quahogs, this mechanism is larger and more grouped, making it more reliable. “Proteins have a higher molecular weight and a more complex structure,” Rodriguez says. “They are more united.”

Thanks to this mechanism, quahogs' mitochondria are less damaged. This is partly because they are more careful about the distribution of the billions of protons and electrons that cross these membranes every second. When electrons leak, they produce reactive oxygen species (ROS), such as hydrogen peroxide, which cause damage. Rodriguez compares it to cars in a traffic jam. In normal mitochondria, a red light at the head of the queue causes cars to reverse, their exhaust gases being released and damaging the environment. However, in the quahog's mitochondria, the traffic light – in this case a protein complex – moves traffic much more efficiently, and less exhaust gases are emitted from the cars.

But it's not just the durable membrane that helps the quahog live a healthy life. This also happens because quahogs mop up any ROS that do leak out. To use Rodriguez's analogy, it's like cleaning car exhaust.

Rodriguez compared the antioxidant capacity of quahog with a number of short-lived related species and found that it 3-14 times more capabilities to destroy ROS. All this adds support to the so-called mitochondrial oxidative stress theory of aging (BRIDGE). It also seems be beyond exceptional life expectancy naked mole rat, who can live 40 yearsmore than six times longer than other rodents of the same size.

Pierre BlierA researcher in animal metabolism and aquaculture genetics at the University of Quebec, he keeps quahogs in aquariums in his laboratory to study the mechanism of their longevity. It confirms that ocean quahogs have a higher ability to buffer oxidants. “Arctic Icelandic has mitochondria that are much more resilient and able to resist ROS,” he says, supporting the MOSTA theory.

This begins to answer the question of how these animals live so long – but what about why? In other words, what selection pressure led to the evolution of such robust mitochondria?

The clue lies in the low oxygen levels in the clam's environment. “Arctic “They can remain with their shell closed, without using their gills to capture oxygen, for about a week,” Rodriguez says. Their mitochondria had to develop ways to survive long periods of low or even no oxygen – called anoxia – and then become strong enough to handle the sudden influx of oxygen and mitigate the sudden increase in oxidative stress that occurs. This is also similar to naked mole rats. “Naked mole rats live in burrows with very low oxygen levels,” Rodriguez says. Rodriguez: “We see similar patterns in that their mitochondria are resilient and adapted to resist anoxia and reoxygenation stress, as well as long life.” So perhaps, he says, selection for anoxia led to longer lifespans, almost as a side effect.

The big question, of course, is whether we can strengthen our own mitochondria. In 2005, a team at the University of California, Irvine created transgenic mice that produced more of the antioxidant enzyme catalase in their mitochondria, and this increased the mice's lifespan by about five months. – a significant amount when the normal life expectancy is two years. Although now it is possible gene editing of human mitochondriaWe are far from understanding how to safely increase life expectancy, so we need another way.

We know that training improves the functioning of our mitochondria. We also know that Tibetan Sherpas, who live at high altitudes, have different mitochondria than those living on the lowlands. A 2017 study looked at indigenous plains people and Sherpas climbing to Everest Base Camp, about 5,300 meters above sea level. The Sherpas were able to use oxygen better and had greater protection against oxidative stress. because their mitochondria were stronger – and it had a genetic basis.

Blier insists that A. icelandica there really is something to tell us about longevity. “My advice for living longer is to take care of your mitochondria: exercise, eat well, and take cold showers… Cold showers seem to trigger mitochondrial quality control mechanisms.”

Well, if it works for the quahogs…