Did you know there is a shark that can live more than 270 years? In my last email I featured a tortoise that was 190 years old, perhaps the oldest land animal. Well, the Greenland shark can live at least 272 years, and possibly 512 years or more.
I'll explain how we know this. Scientists have long guessed that Greenland sharks were old based simply on the fact that they grow only about 1 cm per year, and some are six meters long. But that's just guessing. Other types of sharks can be accurately aged by counting the growth rings on their vertebrae (or on the spines of their fins), but Greenland sharks don't have any hard tissue in their backbones, and they don't have fin spines. So, the ring-counting trick doesn't work.
Recently, though, scientists discovered certain proteins in the eyes of Greenland sharks that form before they are born and do not change throughout their entire lives. They found that they could age the sharks by carbon-dating these proteins. It's important to point out that they didn't catch and kill Greenland sharks specifically for this study. Instead, they used sharks that were accidentally caught in fishermen's nets.
Anyway, one of the sharks they looked at was 5 meters long. Its eye proteins were carbon-dated to be between 272 and 512 years old (carbon dating gives you a range rather than a specific age).
Why do Greenland sharks live so long? Mostly because they live in really cold water and have a really slow metabolism. Here's one more tidbit to blow your mind: Greenland sharks grow so slowly that biologists think they do not even become sexually mature until they are over a century old!
- Greenland shark - Hemming1952, CC BY-SA 4.0, via Wikimedia Commons
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