Saturday, August 13, 2016

The Greenland shark - long-lived behemoth

In nature, large animals tend to be long-lived.  There are exceptions (sponges and clams are among the oldest living animals, and some corals may live over 4,000 years), but whales were the longest-lived vertebrates we knew of. One bowhead whale made it to an estimated age of 211 before (of course) a harpoon ended its career.
Now we find a fish - a shark, to be exact - which lives a low-energy lifestyle in deep cold waters of the Arctic might be the oldest vertebrate anywhere.  The sleeper sharks are probably the world's biggest sharks after the huge filter-feeders, the  whale shark and basking shark.  The Greenland shark, (Somniosus microcephalus) records its age in accumulating tissue layers in the eyeball.  One shark recently tested, a 5-meter giant, was approximately 392 years old. Even more outrageously, that may be the average for Greenland sharks. Somewhere in the dark seas may be a shark 500 years old.
There is some difference of opinion in how many species of sleepers there are (one figure is 17), but they are widespread. The oft-cited website Fish Base says they are found in Arctic, Sub-Arctic, and Sub-Antarctic, waters, plus continental shelves in cold seas, and even in tropical waters.  Pacific sleepers may reach 8m (per a sighting from the submersible Nautile off Japan)  and maybe bigger: if the huge fish sighted by the crew of the submersible Deepstar 4000 in 1968 was, as some authorities think, a sleeper shark, it was estimated at over 10m, maybe over 11.  (If they are wrong - and the crew of two men reported bigger eyes and different tail shape - there is a still-unknown fish the size of a bus out there.)

Kilometers beneath the icy seas off Greenland, the great shark hunts prey near the seafloor. (Image NOAA)

So a tip of the hat to the Greenland shark - and to the animal alive today that might have seen the first post-Columbus Europeans to reach North America sail by.


Nathan said...

Cool article. (I would humbly suggest that eyewitness testimony of large animals is pretty unreliable...)

Still, An average age of over 200 years. Wow.

Can Crusher said...
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Matt Bille said...

Thanks, Nathan! I agree, but still... cue Jaws music...