Why Scientists Are Racing To Uncover The Greenland Shark’s Secrets

2017-07-26T10:01:06+00:00 July 26, 2017|
The Greenland shark can reach more than 15 feet in length and a scale-busting 880 pounds. (Credit: Sharkopedia)

(Click to enlarge) The Greenland shark can reach more than 15 feet in length and a scale-busting 880 pounds. (Credit: Sharkopedia)

Brace yourself. To human senses, the gelid waters of the Arctic and North Atlantic oceans are beyond chilling.

(From Popular Science / by Kendra Pierre-Louis) —  Because sea water is salty, the waters can actually reach temperatures below what we think of as freezing (as low as 28.8 degrees Fahrenheit instead of the usual 32) and remain liquid. Without protective gear, the human body can withstand maybe 15 minutes of these temperatures before succumbing to unconsciousness; 45 minutes before death.

And yet somehow, the Greenland shark—a species that can reach more than 15 feet in length and a scale-busting 880 pounds—calls these waters home. These cartilaginous fish do more than tough out frigid temps: they also resist diseases common in humans, like cancer, and may hold secrets to how we might live longer, healthier lives.

“This particular species of shark is fairly understudied, and is not particularly well known to research—or to anyone except for the Greenlanders,” says Holly Shiels. A physiologist at the University of Manchester, Shiels is fresh off an Arctic expedition where an international group of eight scientists aimed to change that.

 The elusive shark first attracted widespread attention last year, when it graced the cover of the journal Science. Greenlanders—Inuit people who share a lineage with the native populations in the American Arctic—had long said that the Greenland sharkcould live for ages. But last year, Danish researchers confirmed their status as the longest-lived vertebrate (that we know of, anyway). They can live up to 400 years, which raises many questions. Questions, says Shiels, like: “Why don’t they have cancer if they live for that long?”
Cancer is a disease of replication. When our cells copy themselves, they sometimes introduce errors—either because of damage or because they’ve reached the end of their natural lifecycle—that can turn into cancer. Generally speaking, the longer you’ve been alive, the more your cells have replicated. That means more opportunities for these kinds of errors to pop up, which is why cancer is more common in adults. But Jeanne Calment, who holds the record for longest-lived human at 122 years, was a mere child in comparison to the Greenland shark. These creatures don’t appear to hit puberty until they’re 150 years old. We’re not sure how the Greenland shark can accomplish this feat, we just know that it does.

“I came in because they wanted somebody to look at the cardiovascular system,” says Shiels. “Heart disease is a disease of the aged. We know that every year you live past 65 increases your incidence of having heart disease by an exceptionally, ridiculously high rate. So how do these animals continue to beat for 400 years? Do they have fibrosis? Do they have arrhythmia? Do they have any of the things that we associate with aging in human hearts?”

Shiels notes that the purpose of the trip, which she and her colleagues are chronicling after the fact in a series of shark diaries, was simply to observe—to help fill in the blank spots in our understanding of the Greenland shark. Researchers like Shiels are in a race against time to learn as much about the shark as possible, both to help protect the species and to see what aspects of their physiology can improve our understanding of human health and wellbeing.

Why the rush? Because escalating fishing pressures in the North Atlantic and the Arctic mean that increasingly, the Greenland shark has been showing up as bycatch; the unwanted creatures caught on fishing hooks and nets. And juvenile Greenland sharks are scarce. Given that it can take up to 150 years before a female shark can reproduce, we shouldn’t expect that to change radically any time soon. So we might be removing sharks from the ocean at a rate faster than they can be replaced.

Read the full story here: http://www.popsci.com/greenland-shark-secrets