The U.S. just had its birthday, which means it’s been 244 years since the signing of the Declaration of Independence. What if I told you that in the Arctic Ocean, there are sharks swimming around today who were alive in 1776? And before you ask, yes, the very same sharks.
The Greenland shark is an oceanic predator with a lifespan of at least 272 years and could be as long as 500 years, making this animal the longest living vertebrate on the planet. The Greenland shark was a lesser-known species of sharks until 2016, when its extreme longevity was revealed. The finding that they live in the deep, dark polar waters for hundreds of years has captured the imagination of the world and the attention of scientists. How does an animal born in Thomas Jefferson’s time still patrol the deep today?
This extremely long life is particularly interesting with respect to theheart because in people heart disease goes along with aging. In fact, old age is the No. 1 predictor for heart disease in humans, more than smoking, inactivity and obesity.
My colleagues and I wanted to know how the heart of the Greenland shark works and what clues it might hold for understanding extreme longevity. Our approach was to see if sharks showed signs of age-related heart disease like people do.
We found that while the sharks’ heart muscles become stiff—similar to what happens in human aging—they didn’t show signs of coronary artery disease. Coronary artery disease is when cholesterol plaques build up in the vessels that supply blood to the heart, which increases the risk of heart attack.
We have also been exploring the energy centers (mitochondria) and the area that controls cell division (nucleus) in the heart cells that make up the atrial and ventricular chambers of the Greenland shark. These structures are vital for healthy aging and may hold clues to longevity. Our data so far suggest that even in old sharks, the structures look young.
Finally, we turned the question on its head. You may have heard that fish can regenerate their hearts. Maybe the reason these sharks can live so long is that their hearts aren’t old at all but that they continually regenerate. The jury is still out on this idea, but we know that sharks in general are known to have extraordinary immunity and healing powers.
We hope the Greenland Shark will hold the key to cardiac health and long life. However, 25% of all sharks are currently threatened with extinction. We have to work together to protect sharks for the health of our oceans and for the secrets these amazing animals might hold for a long and healthy life.
Holly Shiels, PhD, is an associate professor in animal physiology at the University of Manchester in the U.K. Her research lab studies the mechanisms which maintain or adjust heart function in a changing environment. This knowledge is applied to cardiac health and disease and in predicting how organisms respond to environmental change and stressors.