The Greenland Shark: Meet what could be the longest-living vertebrate
The Greenland shark is a ludicrously late bloomer.
This lazy-looking, Arctic predator reaches sexual maturity when it's about 150 years old. Though more than a century of prepubescence might sound bad, there's a bright side for the sea creature. Once it hits adulthood, it still has another hundred years to live. Maybe even more.
The Greenland shark has a life expectancy of at least 272 years, according to a study published Thursday in Science. If its findings are correct, that makes it the longest-living vertebrate animal in the world, surpassing some sea turtles (about 100 years) tortoises (between 100 and 200 years), and bowhead whales (around 200 years).
Researchers estimated that two of the 28 Greenland sharks they observed were over three centuries old.
"The oldest shark that we've analyzed, it's amazing," said Julius Nielsen, a doctoral candidate at the University of Copenhagen in Denmark and lead author on the study. In their paper they report that it could be 392 years old.
But even that number, 392, doesn't complete the story. The oldest shark could actually be 120 years older, he said. Nielsen and his colleagues used radiocarbon dating and statistical methods to measure the sharks' ages. The tools can only provide accurate age ranges for each specimen, not an exact age.
"We are 95 percent certain that it is between 272 and 512 years," Nielsen said. "This is the first time ever anyone has made an age range of uncertainty of 240 years and they still consider it a success."
Even at the lower end of the range, the Greenland shark still takes the gold for living things with backbones in the old-timers Olympics.
How they did it
To calculate the ages, the researchers studied the eye lenses of each shark they found. The eye lenses first develop when the sharks are still inside their mothers, and as time goes by, they grow like onions, adding layer after layer of tissue. By cutting away the layers and analyzing the nucleus of the center of the eyelens, the team can gauge how old each shark is. Similar techniques have been used to estimate the age of bowhead whales.
All the sharks the team analyzed were females that were already dead. Previous studies had determined that the sharks become sexually mature when they are about 13 feet long. The new study determined that those that size or bigger were at least 150 years old. Males were left out because they were harder to find, but the team thinks life expectancy and the age when they reach adulthood will be similar.
Meet the Greenland shark
Greenland sharks are found throughout the North Atlantic. They are plump and gray, and many have a characteristic parasite latched to the corner of one or both eyes. Researchers aren't sure what the parasites do, but they are ubiquitous among the species.
The sharks are slow-growing, adding about a centimeter a year. The biggest in the study was about 16.5 feet, but they can potentially grow larger than 18 feet. A behemoth that big could be around 400 or 500 years old, according to Nielsen's estimates.
Animals who outlive humans
The longest-living human reached 122.5 years. Here are the top 10 longest living critters:
1. Hexactinellid sponge
One of these Antarctic sponges lived for an estimated 15,000 years.
2. Epibenthic sponge
Another Antarctic sponge that is generally estimated to live 1,550 years.
3. Ocean quahog
This clam, nicknamed "Ming," had its rings measured and it had lived 507 years.
4. Greenland shark
A new study estimates the age of one of these sharks at 392, but it could have been somewhere between 512 and 272 years old when it died.
5. Bowhead whale
One male bowhead living in the Arctic waters was estimated to be 211 years old when it died.
6. Rougheye rockfish
These red fish of the North Pacific have lived to be 205 years old and show little effects of aging in life.
7. Red sea urchin
The spiny critters also don't seem to age much and are estimated to live about 200 years.
8. Galapagos tortoise
These slow moving creatures seen by Charles Darwin have lived as long as 177 years.
9. Shortraker rockfish
These orange-pink fish have lived up to 157 years.
10. Aldabra tortoise and Lake sturgeon
A tortoise that died at a zoo was 152 years old; unconfirmed reports put some of these tortoises living up to 180 years. One lake sturgeon, a bottom-feeder fish, is reported to have lived to be 152.