Negligible Senescence in the Greenland Shark

You may recall that Greenland sharks are extremely long-lived, a trait only comparatively recently discovered as, like many marine species, these sharks are nowhere near as well studied as tends to be the case for larger land animals. Researchers have now started in on the process of trying to understand why this is the case. As reported here, initial measurements of muscle metabolism show little variation with age. An absence of declining function with age over near all of a lifespan is characteristic of many long-lived species. It remains to be seen as to whether studying the biochemistry of these unusually long-lived species will yield means of enhancing longevity in humans in the near term of the next few decades. It is too soon to say, even if commenting on the much more extensive study of long-lived mammalian species such as the naked mole-rat.

Greenland sharks (Somniosus microcephalus) are the longest living vertebrate with an expected lifespan of at least 270 years and possible lifespan beyond 500 years. Previously it was thought that this long lifespan was due to the shark's cold environment and minimal movement, but the factors behind this species extreme longevity appear to be far more complex - prompting researchers to investigate alternative theories. "Most species show variation in their metabolism when they age. We want to determine if Greenland sharks also show this traditional sign of aging or if their metabolism remains unaltered over time."

To measure the metabolism of the sharks, researchers conducted enzyme assays on preserved muscle tissue samples from Greenland sharks. They measured the metabolic activity of these enzymes with a spectrophotometer across a range of different shark ages and environmental temperatures. Surprisingly, researchers found no significant variation in muscle metabolic activity across different ages, suggesting that their metabolism does not appear to decrease over time and may play a key role in their longevity. The results of this study also show that 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."