Scientists Say Greenland Sharks May Live 400 Years

NOAA, Flickr // CC BY-2.0
NOAA, Flickr // CC BY-2.0

Get ready to feel like a baby: There may be sharks alive today that are older than the United States. Like, much older. Researchers found a Greenland shark that’s around 392 years old—and 27 others with an average age of 272 years old. They published their findings today, August 11, in the journal Science. 

Young or old, Greenland sharks (Somniosus microcephalus, literally “tiny-headed sleeper”) are extraordinary creatures. They’re the second-largest carnivorous sharks in the world, reaching 2500 pounds. Their teeth are shaped and angled to remove plugs of flesh from their prey, and their own flesh is poisonous. 

Even so, Greenland sharks, like most sharks, present no risk to humans. They’re incredibly slow swimmers and live deep, deep down in the icy waters of the Arctic Ocean. These qualities make them both fascinating to scientists and tricky to track and study. And without data, it’s hard to argue that the sharks need protection.

Julius Nielsen

Previous studies had already found these sharks to have astonishingly long lives. The last estimate, based on a shark caught in 1952, concluded that they could live to be at least 200 years old. 

Science has come a long way since the 1950s, and researchers decided it was time to check again. Fortunately, they had access to a good number of Greenland sharks; unfortunately, that’s because those sharks had been accidentally caught in fishing nets and scientists’ long lines between 2010 and 2013. All 28 female sharks used in the study had been fatally injured by the time they landed onboard—some by other sharks, and some by fishing equipment—and so all were euthanized. After the sharks’ deaths, researchers measured each shark and took tissue samples from the lenses of its eyes. 

The scientists used radiocarbon dating on the samples to see if they could age the sharks. Once again, they had good data thanks to a bad situation—in this case, nuclear warfare. Scientists have known since the 1950s that nuclear bomb tests leave permanent molecular marks on sea creatures. Consequently, the appearance of bomb-related changes in an animal’s tissue can be seen as a sort of time stamp. But because these changes persist, even animals born after any given bomb can be marked by it if the animals they eat were alive during the test. 

By combining this information with the sharks’ body measurements, the scientists were able to estimate each animal’s approximate age. The youngest sharks sampled were less than 10 feet long and under 100 years old. These were mere pups for Greenland sharks; the data suggested that these animals don’t even reach sexual maturity until they’re around 150 years old. 

The oldest two sharks were 16 feet long apiece, and the scientists estimated their age at 335 (plus or minus 75 years) and 392 (plus or minus 120 years). Considering these averages, the researchers say, a conservative estimate of the shark’s longevity would put them at about 272 years old—still making them the oldest vertebrates on the planet. 

Given these astonishing findings and the threats posed to Greenland sharks by commercial fishing, the authors write, it’s time we start thinking about how to protect them.

Know of something you think we should cover? Email us at tips@mentalfloss.com.

 

The Horrors of Anglerfish Mating

Masaki Miya et al. "Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective," BMC Evolutionary Biology 10, article number: 58 (2010), Wikimedia Commons // CC BY 2.0
Masaki Miya et al. "Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective," BMC Evolutionary Biology 10, article number: 58 (2010), Wikimedia Commons // CC BY 2.0

When you think of an anglerfish, you probably think of something like the creature above: Big mouth. Gnarly teeth. Lure bobbing from its head. Endless nightmares. 

During the 19th century, when scientists began to discover, describe, and classify anglerfish from a particular branch of the anglerfish family tree—the suborder Ceratioidei—that’s what they thought of, too. The problem was that they were only seeing half the picture. The specimens that they were working with were all female, and they had no idea where the males were or what they looked like. Researchers sometimes found some other fish that seemed to be related based on their body structure, but they lacked the fearsome maw and lure typical of ceratioids and were much smaller—sometimes only as long as 6 or 7 millimeters—and got placed into separate taxonomic groups.

It wasn’t until the 1920s—almost a full century after the first ceratioid was entered into the scientific record—that things started to become a little clearer. In 1922, Icelandic biologist Bjarni Saemundsson discovered a female ceratioid with two of these smaller fish attached to her belly by their snouts. He assumed it was a mother and her babies, but was puzzled by the arrangement.

“I can form no idea of how, or when, the larvae, or young, become attached to the mother. I cannot believe that the male fastens the egg to the female,” he wrote. “This remains a puzzle for some future researchers to solve.”

When Saemundsson kicked the problem down the road, it was Charles Tate Regan, working at the British Museum of Natural History in 1924, who picked it up. Regan also found a smaller fish attached to a female ceratioid. When he dissected it, he realized it wasn’t a different species or the female angler’s child. It was her mate.

The “missing” males had been there all along, just unrecognized and misclassified, and Regan and other scientists, like Norwegian zoologist Albert Eide Parr, soon figured out why the male ceratioids looked so different. They don’t need lures or big mouths and teeth because they don’t hunt, and they don’t hunt because they have the females. The ceratioid male, Regan wrote, is “merely an appendage of the female, and entirely dependent on her for nutrition.” In other words, a parasite.

When ceratioid males go looking for love, they follow a species-specific pheromone to a female, who will often aid their search further by flashing her bioluminescent lure. Once the male finds a suitable mate, he bites into her belly and latches on until his body fuses with hers. Their skin joins together, and so do their blood vessels, which allows the male to take all the nutrients he needs from his host/mate’s blood. The two fish essentially become one.

With his body attached to hers like this, the male doesn't have to trouble himself with things like seeing or swimming or eating like a normal fish. The body parts he doesn’t need anymore—eyes, fins, and some internal organs—atrophy, degenerate, and wither away, until he’s little more than a lump of flesh hanging from the female, taking food from her and providing sperm whenever she’s ready to spawn.

Extreme size differences between the sexes and parasitic mating aren’t found in all anglerfish. Throughout the other suborders, there are males that are free-swimming their whole lives, that can hunt on their own and that only attach to the females temporarily to reproduce before moving along. For deep-sea ceratioids that might only rarely bump into each other in the abyss, though, the weird mating ritual is a necessary adaptation to keep mates close at hand and ensure that there will always be more little anglerfish. And for us, it’s something to both marvel and cringe at, a reminder that the natural world is often as strange as any fiction we can imagine.

Naturalist William Beebe put it nicely in 1938, writing, “But to be driven by impelling odor headlong upon a mate so gigantic, in such immense and forbidding darkness, and willfully eat a hole in her soft side, to feel the gradually increasing transfusion of her blood through one’s veins, to lose everything that marked one as other than a worm, to become a brainless, senseless thing that was a fish—this is sheer fiction, beyond all belief unless we have seen the proof of it.”

This Automatic Fetch Machine Will Keep Your Dog Occupied When You Don't Have Time to Play

iFetch
iFetch

Every dog owner knows that it's impossible to keep up with a pooch that's always looking to play. But if you want to keep them active while still having time for yourself, there's the iFetch, a toy that will automatically throw tennis balls, allowing your canine to play fetch whenever they please.

You can find the iFetch Original, which is ideal for small or medium dogs, on Amazon for $115. The Original can either be charged with an AC adapter or run on six C batteries, both of which are included. You can adjust the settings on the iFetch to throw the ball 10, 20, or 30 feet, making it perfect for indoor or outdoor play. Once it's charged and the distance is set, let your canine drop a tennis ball into the machine and it will take care of the rest.

If you have a large dog, look for the iFetch Too, which is available on Amazon for $200. This model has a rechargeable battery that can last up to 300 throws. This model can launch the ball 10, 24, or 40 feet, and it also comes with a custom option, so you’ll find room for your dog to play no matter how much space is available.

If your dog loves their new toy, but you don't love finding slobbery tennis balls around the house, check out the company’s medium- and small-size slobber-proof balls.

It may take time for your canine to learn how to use the toy, but the company has some training tips from Nicole Ellis, a certified professional dog trainer. To start, it's recommended that your dog knows the “drop it” command. If they don’t, check out their training tips here. After your dog has mastered that command, the company has plenty of tricks, such as keeping training sessions short and ending them on a positive note. For more ideas, check out their page.

Once you set up your iFetch and watch your furry friend run back and forth, you may start to wonder why they like fetch so much. According to research on the subject, when dogs exercise, neurotransmitters stimulate reward regions in their brain, which is much like when humans experience a "runner's high."

If you happen to notice your canine seems particularly athletic while they are chasing the ball back and forth, check out these other sports they can play.

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