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Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more . The Greenland shark is known to be elusive, for years effectively hiding its most astounding traits.
The sluggish creatures lurk primarily in the deep, cold waters of the North Atlantic and Arctic oceans , and are the only sharks to withstand the freezing temperatures year-round. Some individuals of the species might have been swimming there since colonial times — and researchers are just beginning to unravel how. Due to the marine animal’s slow metabolism, scientists long suspected that the Greenland shark had an unusually lengthy lifespan, but there was no way to determine the exact magnitude until recently.
Research published in 2016 determined the sharks are the longest-living vertebrates, likely living to be around 400 years old, with the estimate ranging from 272 years old to over 500 years old. Now, a different study aims to understand the mechanism behind that longevity. An international team of scientists has become the first to map the Greenland shark’s genome, sequencing about 92% of its DNA and providing insight into the inner workings of the long-lived fish.
Not only does the assembly, the computational representation of its genome, add to what’s known about the sharks’ structure and how their bodies function, but it also provides clues to why the animals have such staying power, the researchers said. “Only with the genome assembly we can really understand which, for instance, mutations have accumulated in the shark that led to this enormous lifespan,” said Dr. Steve Hoffman, senior author of new research on the Greenland shark and a computational biologist at the Leibniz Institute on Aging in Germany.
“To this end, this genome is some kind of a tool, if you will, that allows us, and of course also other researchers, to look into these molecular mechanisms of longevity.” The study authors released their findings as a preprint — a scientific paper that has not gone through the peer-review process — as they invite more scientists to study the genome and conduct their own analysis of the shark’s DNA, Hoffman said. There are few species of animals that live longer than humans do, particularly in comparison with our body weight and size.
By studying the longevity mechanisms of the Greenland shark, scientists could also gain more insight into how to potentially extend the human lifespan, the authors said. Greenland sharks grow at an extremely slow rate of less than 1 centimeter (0.4 inch) a year but eventually can reach more than 6 meters (about 20 feet) in length, and they don’t reach sexual maturity until they are more than a century old.
It’s suspected that the oldest of the species could survive over half a millennium. The study authors found the shark’s genome to be extraordinarily large, twice as long as a human’s and bigger than any other shark genome sequenced to date. The researchers are analyzing the genome to explore what its large size may mean for the shark’s longevity.
One reason for a longer genome might come down to the shark’s ability to repair its DNA, a trait that has commonly been seen in other species with exceptional lifespans, including the naked mole rat, the longest-living rodent that endures up to 30 years or more, and certain species of tortoises that can live to be more than 100. The Greenland shark is unique in that a vast amount — more than 70% — of its genome is made up of jumping genes , which can move within the DNA sequence by duplicating themselves, sometimes creating mutations. Often, these duplications are referred to as genetic parasites due to their potential harmful effects, including genetic diseases such as cancer.
However, it seems that in the Greenland shark, the genes that repair DNA have been acting as jumping genes, distributing themselves into the genome and slowing down the aging process by fixing damaged DNA. As a result, “the detrimental effect of these transposable elements (jumping genes) is not only canceled out, but maybe even reversed so that the genome integrity is even better in the Greenland shark,” said lead author Dr. Arne Sahm, a bioinformatician and junior professor at Ruhr University Bochum in Germany.
The authors suggest that DNA repair genes in the species at some point evolved the ability to multiply, further contributing to DNA repair and in turn longevity. The researchers want to explore and analyze the Greenland shark’s DNA further, while also comparing its genome with other shark species and shorter-lived fish, to provide additional evidence for this unique trait, Hoffman said. Before the researchers sequenced the Greenland shark’s genome, only about 10 genomes were available for all elasmobranchs — a subclass of fish including sharks, rays and skates — said Dr.
Nicole Phillips, an associate professor of ecology and organismal biology at the University of Southern Mississippi in Hattiesburg. Phillips was not involved in the research conducted by Hoffman, Sahm and their team. “The more high-quality genomes that are sequenced, the better we can understand the genetic underpinnings of shared as well as unique traits of this ancient group,” Phillips said in an email.
“Identification of the genetic basis of lifespans across different species, including long-lived sharks, allows researchers to understand the biology of aging and longevity.” Because of the sharks’ preference for deep waters, historically most information on the Greenland shark came from commercial fishing records. In the past decade, researchers have increasingly used video, including remotely operated vehicles and baited cameras, as well as observations in captured specimens to research the elusive shark.
To sequence and study the shark’s genetic makeup, the authors euthanized several specimens to obtain tissue sample, for which they had a research permit. But the scientists hope their work on the Greenland shark genome will ultimately help the species’ conservation, Hoffman said. The Greenland shark is currently listed as vulnerable on the International Union for Conservation of Nature’s Red List of Threatened Species, with its last assessment in June 2019.
“The authors were able to get insight into an animal that really sits at a unique place in the evolutionary tree of life. It’s very ancestral, and so it could basically represent, at least in sharks, potentially how all genomes evolved, because it provides this snapshot of a really interesting, very specialized genome,” said Dr. Toby Daly-Engel, an associate professor of ocean engineering and marine sciences at the Florida Institute of Technology in Melbourne and director of the Florida Tech Shark Conservation Lab.
Daly-Engel was not involved with the research. “On the one hand, I think that the insight into these jumping genes is really interesting, and yet, on the other hand, it’s not surprising that they’re seeing things that we’ve never seen before,” she added, “because even though we’ve sequenced other shark genomes, shark species are so different from each other that we can expect new things with every species.” In earlier research, scientists have been able to extend the lifespan of certain short-lived species, such as flies and mice, by using genetic modifications.
By researching more long-lived species, scientists can have a better understanding of the aging process for all species and the tool kits that could potentially be applied to prolonging human lifespans, Sahm said. “Evolution doesn’t always choose the same path. So if, let’s say, the goal is to have better DNA repair, but it can be achieved by multiple mechanisms, and the mechanisms are different in mole rats and whales and sharks, we need to learn about all of them and then see which ones we can maybe more easily adapt for human use,” said Dr.
Vera Gorbunova, a professor of medicine and biology at the University of Rochester in New York and the lead author of a 2023 study that used transferred naked mole rat genes to extend the lifespan of mice. Gorbunova was not involved in the Greenland shark research. “Once researchers understand the mechanism .
.. then we can see if we can design a specific drug to target this genome enzyme in this way,” she added.
“You can dream about gene therapy, maybe we can give people a gene from Greenland shark, but that may be more science-fiction type of approach, but something more readily translatable would be, well, maybe we can design a drug that targets (a) human gene and makes it work a little bit more like that of a Greenland shark. And that would ..
. improve DNA repair in humans.” There are a lot of environmental influences that damage human DNA, such as sunlight or smoking.
By learning more about the Greenland shark’s unique DNA repair technique, scientists can begin to study how the trait contributes to other age-delaying factors such as tumor suppression in Greenland shark cells as well as potential effects on the cells of other species, including our own, Sahm said. “If we really want to increase the human lifespan significantly, or maybe even better, to extend the percentage of our life (in which) we are really healthy and fit and can do things ..
. it’s good to look at the tricks of very long-lived animals,” he added, “how they change their system overall, which strategies that they use and then to learn from ..
. those strategies.”.
