Scientists with the Minderoo-UWA Deep-Sea Research Centre were stunned when they captured for the first time a shark cruising through Antarctic waters. The shark was recorded swimming in the South Shetland Islands near the Antarctic Peninsula. It was at a depth of 1,640 feet in near-freezing waters, at 34.29 degrees Fahrenheit. The shark in question was around 10-13 feet long and belongs to the Sleeper shark family, though it is unknown what specific species of Sleeper shark it is. Up to this point, it was believed that sharks could be found on every continent except Antarctica. This is an extraordinary find, as we have never discovered a shark this far south on the globe.
Many people wondered how a shark survives such frigid temperatures. Well, sleeper sharks’ bodies are built for living in cold waters. Sleeper sharks have adapted to these temperatures by having an incredibly sluggish metabolism. They process food so slowly that they are able to conserve energy very efficiently, allowing them to stay warm in freezing temperatures. This form of energy conservation allows us to live incredibly long lives, at the cost of being required to live life in the slow lane. For example, one of the most famous members of the sleeper shark family is the infamous Greenland shark. They swim at a top speed of less than 2 miles per hour, grow less than a centimeter in length a year, don’t reach sexual maturity until 150 years of age, and can be pregnant for 8-18 years. But what the Greenland shark is most famous for is their lifespan. Greenland Sharks have been known to live anywhere from 200 years to 500 years! This gives them the record for the longest lifespan of any vertebrate that we know of. This is due to their frigid environment and slow metabolism. According to National Geographic, “A recent study of their genome found duplicates of genes related to DNA repair, immune function, and protection against oxidative stress, all of which reduce the physical toll of time.”
Another strategy that Sleeper Sharks have to live in cold waters is the contents of their tissue. Sleeper sharks have Urea in their flesh, which helps them keep osmotic balance with the seawater they swim in. Though the Urea may destabilize the shark’s protein, this problem is fixed by trimethylamine N-oxide, or TMAO, which stabilizes those proteins. While all sharks have TMAO, Sleeper sharks have much higher amounts, which is another factor in their ability to live in near-freezing waters. With all of these adaptations, it’s truly exciting but not too surprising to see one near Antarctica.
The team of researchers that captured the Sleeper shark on camera was incredibly lucky, as Sleeper sharks are notorious for being very elusive. Not only do Sleeper sharks live in very cold water, but they also live at incredible depths where little to no sunlight reaches them. This makes reaching where they live very difficult, as it takes a lot to travel through such harsh conditions. And if someone manages to do that, they then face the challenge of finding a shark down there. And since it’s so dark, it’s very difficult to navigate through the water, making running into a shark, or any life in general, very difficult and luck-dependent. With this discovery of a shark on the only continent we believed they couldn’t inhabit, we can learn more about the elusive Sleeper shark family, as well as sharks as a whole. One thing we know for sure about sharks is that no matter how far or deep you are in the sea, you just can’t escape the ocean’s most successful predator.
