A recent study of a shark's eye concluded that a 400-year-old Greenland-vertebrate is the longest living on earth. A total of 28 animals were studied through extensive research and radiocarbon dating technology, and it was estimated that a particular female was four centuries old.
Some of the spectacular findings revealed that sharks grow only 1cm long a year and that they attain sexual maturity only at the age of 150 years. The findings were recently published in the journal science that further throws light on the special ways invented now to determine the age of sharks in contrast to the techniques used earlier.
Julius Nielsen, who is a marine biologist from the University of Copenhagen opines, "We had our expectations that we were dealing with an unusual animal, but I think everyone doing this research was very surprised to learn the sharks were as old as they were."
Greenland sharks can grow up to a length of 5 meter over its lifetime. They are huge beasts and spend most part of their lives in the cold, deep waters of the North Atlantic. The sluggish growth rate and leisurely pace of life of the sharks convinced scientists that the vertebrates lived long, but there were no technology to determine their exact age.
Scientists have been able to examine otoliths in some fish to determine their age, but Greenland sharks are very soft and they have no hard body parts where their growth layers can deposit over the time. After some clever inspection, scientists found that a shark's eye lens consists of a kind of specialized material that is full of proteins. These proteins are metabolically inert, BBC reported.
Radiocarbon dating fail to produce the exact age of sharks as the youngest age determined can be as low as 272 and the oldest age is 512. "Even with the lowest part of this uncertainty, 272 years, even if that is the maximum age, it should still be considered the longest-living vertebrate," according to Julius Nielsen, a well-known marine photographer.
Mr. Nielsen further explains the unique eye structure of Greenland sharks. He says that the lens grows over the entire lifetime of the animal. As the animal gets older, more layers are gradually added to the lens. Scientists count all the layers until they reach the embryonic nucleus that lies in the center of the eye, National Geographic reported.
Here is a video demonstration of Greenland shark, the longest living vertebrate: