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Greenland sharks are among nature’s least elegant inventions. Lumpish, with stunted pectoral fins that they use for ponderously slow swimming in cold and dark Arctic waters, they have blunt snouts and gaping mouths that give them an unfortunate, dull-witted appearance. Many live with worm-like parasites that dangle repulsively from their corneas. They belong, appropriately enough, to the family Squalidae, and appear as willing to gorge on fresh halibut as on rotting polar bear carcasses. Once widely hunted for their liver oil, today they are considered bycatch. For some fishermen, a biologist recently told me, netting a Greenland shark is about as welcome as stepping in dog poop.
And yet the species has an undeniable magnetism. It is among the world’s largest predatory sharks, growing up to eighteen feet in length, but also among its most elusive. Its life history is a black box, one that researchers have spent decades trying in vain to peer inside. Where do Greenland sharks mate? What is their global range and population structure? And, most enticing of all, how long do they live? A study begun in the nineteen-thirties suggested that the species’ lifespan might well be extraordinary, based on the slow growth rate of a single shark that a scientist was lucky enough to catch twice. Verifying this, however, proved nearly impossible. To determine age in other sharks, biologists count the growth rings on their fin spines and vertebrae. But Greenland sharks have no hard tissues in their bodies; even their vertebrae are soft. The longevity question seemed unanswerable.
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Using carbon dating and a new method involving proteins in the lens of the eye, Danish scientists have unraveled the mystery of how long Greenland sharks live. Photograph by WaterFrame / Alamy
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