In their constant search for the secret to eternal youth or any formula that could help them live longer, humans have often studied creatures that outlive them. In this group of extraordinary creatures, one stands out as the only vertebrate able to roam the planet for over 500 years. Recent scientific discoveries have shed new light on the longevity of this remarkable creature: the Greenland shark.
A new study. A team of researchers from the University of Manchester recently conducted an experimental test to determine the key factor contributing to the incredible longevity of the world’s oldest living vertebrate species. The scientists found that the metabolic activity of their muscles is a vital factor. Now, these findings could potentially be applied to species conservation in the face of climate change and may also have implications for human cardiovascular health.
A centenarian shark. In August 2016, a study published in Science presented a new record-holder for the world’s longest-living vertebrate, surpassing Arctic whales. This creature is the Greenland shark, also known as the gurry or grey shark. By dating the crystalline nuclei of 28 female Greenland sharks, the researchers calculated a life expectancy of at least 270 years and a potential lifespan of over 500 years, setting a new record for vertebrate longevity.
Metabolism. The latest study started with well-known facts. Namely, most species show variations in their metabolism as they age. Initially, the scientific community thought that sharks’ long lifespan was due to the cold environment and minimal movement. However, the factors behind the species’ extreme longevity appear to be much more complex.
Ewan Camplisson, the study’s principal investigator, states, “We wanted to determine if Greenland sharks also show this traditional sign of aging or if their metabolism remains unaltered over time.” To measure metabolism, the team performed enzyme assays on preserved muscle tissue samples from the species. They used a spectrophotometer to measure the metabolic activity of enzymes at different ages and environmental temperatures.
Muscles are maintained over time. Researchers made surprising findings, especially when compared to other species. The results showed no significant differences in muscle metabolic activity at different ages, suggesting that sharks’ metabolism doesn’t decrease over time. This suggests that stable metabolic activity could be crucial to their longevity.
“By showing that [Greenland sharks’] metabolism doesn’t seem to alter with age in their red muscle, I think this shows the shark has a range of adaptations which together lead to its long lifespan,” Camplisson told Interesting Engineering. “The results support our hypothesis that the Greenland shark does not show the same traditional signs of aging as other animals,” he adds.
Enzymes and cold. Additionally, the work also suggests another element that may help explain the creature’s extraordinary longevity. The Greenland shark’s metabolic enzymes were significantly more active at higher temperatures. “This would suggest that the shark’s red muscle metabolism is not specially adapted for the polar environment, otherwise we would have expected to see less of a temperature related difference in activity,” Camplisson says.
Climate change. Climate change is a crucial factor affecting not only the Greenland shark, but all the planet’s animals. In today’s rapidly changing climate, species with long lifespans and limited adaptability are at greater risk of extinction.
The study reveals that female Greenland sharks, which may not reach sexual maturity until 150 years of age, have long generation times that significantly reduce their ability to adapt to human-induced environmental changes.
Conservation. Camplisson and his team suggest a more specific plan, such as controlling the expansion of fishing in Arctic waters: “With the loss of ice in the Arctic, new fishing regions are opening and these should be monitored very closely to determine rates of bycatch of Greenland sharks.”
Not just that. According to their findings, tracking these bycatch rates would not only provide insight into where shark populations are found in greater numbers but also help assess whether warming waters are forcing sharks to move to a smaller and smaller region with colder water.
Human diseases. Lastly, the discovery of the keys to shark longevity may also have implications for future research on human beings. Studying sharks’ cardiovascular and metabolic activity could provide valuable insights for health-related research. However, according to Camplisson, “a shark’s cardiovascular system varies significantly from humans.” So, “making direct comparisons between the whole systems is not easy.”
Researchers hope to identify the metabolic adaptations that enable sharks to maintain consistent activity as they age. “A big factor to investigate is mitochondrial dysfunction and if Greenland sharks show any signs of this at all,” they conclude. By studying how the heart of these creatures work, scientists aim to understand human cardiovascular health better.
Image | NOAA| Hemming1952
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