We usually think of turtles when we think of animals that can live for a long time. But a team of scientists lead by University of Copenhagen has discovered that Greenland shark can live for 400 years, with one female estimated to be 392 years old. That means that there might be live sharks that had been born not long after William Shakespeare did his writing!
The species can grow to 21 feet (6.4 meters) length and is the longest living vertebrate in the world. However, the biology of the shark is still poorly understood by science. The Greenland shark is one of the slowest sharks, but it's still a predator that feeds on fish and smaller sharks.
Also, the usual method for measuring the age of the shark – counting seasonally deposited growth layers in fin spines and other hard calcified structures - didn't work on this shark. Instead, the scientists analyzed the eye lens nucleus of 28 female sharks that were accidentally caught during Greenland Institute of Natural Resources' annual fish and shrimp surveys.
The center of shark's eye lens is made from metabolically inactive tissue, which doesn't change much in shark's life. So the scientists measure the radiocarbon content in the lenses and matched the data to radiocarbon changes in marine food in North Atlantic. "We used established radiocarbon methods but combined them in a new way," said the lead scientist of the study, Julius Nielsen from the University of Copenhagen and the Greenland Institute of Natural Resources. "This approach, along with the extraordinary ages for these sharks, makes this study highly unusual."
Scientists think that Greenland sharks grow so old because they're big and they grow really slowly – no more than 1/3 of an inch (or 1 cm) a year. Two of the largest sharks in the study measured 16.17 feet (4.93m) and 16.47 feet (5.02m) respectively and were determined to be roughly 335 and 392 years old. The theory now is that a fully grown Greenland shark female that measures over 16 feet (5 m) will live to at least 272 years. Their childhood is really long, too, with an average shark maturing only at 156.