It was long thought that Greenland sharks, which lived very, very long lives, were practically blind. But a new study reveals that they can not only see, but also retain their vision into old age.
By Jackie Flynn Mogensen edited by Claire Cameron
Photo by: Martin Zwick/REDA/Universal Images Group via Getty Images
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Greenland sharks are a biological anomaly. The animals can grow over 20 feet long, weigh over a ton, and live nearly 400 yearswhich makes this species the longest-lived species vertebrate on the planet-a fact that could help uncover secrets improve longevity.
And now, in a study published this week In Natural communications, Scientists have looked at one of the most remarkable features of the Greenland shark: it has functional eyes and, more remarkably, maintains its vision until senescence.
Biologists have long believed that these sharks are virtually blind, in part because of their tendency to attract parasites that attack them and lodge in their corneas. But this work challenges that belief, the researchers write, showing that even centuries-old Greenland sharks retain a visual system “well adapted to life in dim light.”
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“From an evolutionary perspective, you don’t keep the organ you don’t need,” said Dorota Skowronska-Krawczyk, an associate professor of physiology and biophysics at the University of California, Irvine and co-author of the paper. in a statement. “After watching many videos, I realized that this animal was moving its eyeball towards the light.”
Skowronska-Krawczyk and her colleagues analyzed samples taken from sharks more than a century old and found no obvious signs of retinal degeneration, which she notes is a “remarkable” finding, given their advanced age.
The researchers say this work provides a starting point for future research into how sharks preserve their vision over such long periods of time, work that could eventually inform studies of age-related vision loss in humans and how to prevent it.
“Not many people work on sharks, especially their vision,” said Emily Tom, a Ph.D. student at the University of California, Irvine, who is also a co-author of the study, in the same statement.
“We can learn a lot about vision and longevity from long-lived species like the Greenland shark,” Tom said.
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