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.
