The average human lifespan is about 73.4 years. This number seems tiny compared to the Greenland shark’s potential lifespan of over 500 years. These sharks, which live in the cold, deep waters of the North Atlantic and Arctic Oceans, live longer than any other known vertebrate. This puts the oldest Greenland shark alive at the same time Galileo built the first telescope. Some sharks may have been puppies when Shakespeare wrote Hamlet.
It turns out that these organisms are not only living history, but could also provide valuable insights into human health and the protection of vulnerable species in the face of climate change.
Speaking at the Society for Experimental Biology annual meeting in Prague, researchers found that metabolic activity in the muscles of western lowland sharks remains constant as they age — a finding that contrasts with most other species, where metabolic rate typically declines over time, leading to aging and the health problems that come with it.
This discovery is not only interesting from an oceanographic point of view, but could have more ramifications for human life underwater: it may answer some questions about cardiovascular health.
“We want to understand what adaptations enable western lowland sharks to live such long lives,” says Euan Camplison, a PhD student at the University of Manchester. “Most species experience changes in their metabolism as they age. We want to understand whether western lowland sharks show these classical signs of ageing, or whether their metabolism remains unchanged over time.”
Previously, scientists thought the shark’s longevity was due to its frigid environment and limited movement, but the mechanism responsible for this species’ incredible longevity appears to be much more complicated.
Camplison and his team tested muscle samples to see how active certain enzymes were. They looked at samples from Greenland sharks of different ages and at different temperatures. To their surprise, they found that the activity of the enzymes remained the same regardless of the shark’s age. This suggests that a shark’s metabolism doesn’t slow down as they get older, which may explain their long lifespan.
“This is quite different from most animals, who tend to show some changes in metabolic enzyme activity as they age,” Camplison said. “The results support our hypothesis that Greenland sharks do not show the same signs of aging as other animals.”
Furthermore, the study showed that metabolic enzymes in Greenland sharks show greater activity levels at higher temperatures, indicating that their muscle metabolism is not clearly adapted to polar environments, which could impact their survival if their natural habitat warms due to climate change.
Human health effects
The impact of this research goes beyond marine biology.
“By studying Greenland sharks and their hearts, we may be able to better understand our own cardiovascular health,” he says. “These are problems that become increasingly common and severe as we age.”
Human and shark hearts are structured differently—shark hearts have two chambers while humans have four—but there are similarities at the cellular level that could provide valuable new knowledge. If scientists can figure out why Greenland shark hearts are able to avoid the normal decline that comes with age, they may be able to use their findings to improve human heart health, particularly in the treatment of heart disease.
Heart disease often results from the destruction of heart tissue and reduced metabolic efficiency, and by applying what scientists have learned from Greenland sharks, researchers may be able to develop treatments that keep the heart muscle functioning well, which could potentially reduce the risk of heart disease in older adults.
What’s more, understanding how Greenland sharks maintain a stable metabolism without showing signs of aging could lead to advances in treating age-related conditions in humans. For example, researchers may be able to develop treatments to keep older people’s metabolism healthy and reduce their risk of heart disease.
Researchers may also be able to study specific enzymes that remain active in the Greenland sharks to better understand their structure and function. If scientists can replicate or mimic these enzymes in humans, they could help maintain muscle and heart health and slow the aging of human tissues.
Investigating the genetic reasons behind the longevity and stable metabolism of Greenland sharks may also uncover important genes and pathways that promote longevity and health. These genetic factors could lead to new gene therapies and drugs that target these pathways in humans, helping the medical community maintain cardiac health and metabolic function as we age.
Conservation concerns
But the study also highlights the Greenland shark’s vulnerability to climate change: As ocean temperatures rise, the survival of this species, which takes around 150 years to reach sexual maturity, is under great threat. Its slow reproductive rate and long generation period make it particularly susceptible to environmental changes.
“Due to its long generation time, this species will have much less opportunity to adapt to anthropogenic changes in its environment,” Camplison said.
In a world where climatic conditions are rapidly changing, long-lived species that are unable to adapt may be most at risk of extinction.
Camplison plans to expand his research and test more enzymes and tissue types to better understand the sharks’ metabolic activity.
“My ultimate goal is to conserve this species, and the best way to do that is to understand it better,” he said.
By studying these sharks holistically, scientists hope to develop strategies to mitigate the effects of climate change and other threats. Understanding the lifespan and resilience of Greenland sharks will provide broader insights into biological aging and adaptation.
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