Greenland sharks have had a very special place in the hearts of researchers as emblems of longevity for living in the Arctic and North Atlantic Oceans, mysterious creatures. Those ancient animals, living for more than 500 years, have been provoking researchers for generations. Groundbreaking research has finally revealed what underlines their incredible longevity: unwavering metabolism.
Greenland sharks are of the Somniosus microcephalus type and have been recovered as low as 8,684 feet in the frozen depths of both the Arctic and North Atlantic, living at least 250 years on average, with some turning over five centuries, making it the vertebrates on Earth that live the longest.
For decades, scientists have shown that sharks relate to cold habitats where generally little movement happens. However, new findings presented at the Society of Experimental Biology Conference in Prague overturned these findings. Research pointed out that, unlike other animals where metabolism gets increased as a result of aging, this metabolic activity remains the same in sharks.
“This is important for us because it means the sharks do not show the classic signs of aging,” said Ewan Camplisson, a Ph.D. student at the University of Manchester and the paper’s lead author. In most animals, metabolic rates decrease over age, and less energy is produced, with slower cellular repair processes and accumulation of cellular waste. Not so with Greenland sharks.
They did this by sampling shark muscle tissue from 23 Greenland sharks off the south coast of Disko Island in central Greenland. Their metabolic rates and their responses to different environmental temperatures were estimated from this by the activities of five different enzymes. Their ages, estimated by measuring body length, ranged between 60 and 200 years old.
Astoundingly, this activity by the enzyme turns out to be age-invariant. “In most animals, you would expect to find some enzymes have lower activity at older ages because they wear out or become less efficient,” said Camplisson. Such stability in metabolic activity tells that Greenland sharks don’t go through the normal degenerative aging process.
That the optimal temperature for the sharks’ enzymes was way much higher. Although this is generally so for the enzymes, it does present another problem for these ancient creatures in light of global warming. In case the sea surface temperatures are to rise by 2.1 to 5.8 degrees Fahrenheit in 2100, then this will have a large effect on shark’s metabolism, which in turn could be a change of lifestyle and eventually of survival.
Camplisson added that further research was needed to know the full implications of these findings. “We would like to investigate more hallmarks of aging and further study the sharks’ metabolism to better protect them as global warming affects their environment,” he said.
The findings have implications beyond just the biology of this species. Knowing how Greenland sharks keep their metabolism in check might tell us much about how human beings age and age-related diseases. Though we are never going to live as long as these sharks, even small increases in human life expectancy should be a huge discovery.
Although this fast-changing environment no longer favors the pace of life that was for a very slow and steady Greenland shark, the wonders of its biology do give a glance into the scientist’s imagination facing an uncertain future, along with a look at secrets of aging and survival.