New scientific research reveals that Greenland sharks, the longest-living vertebrates known to science with lifespans reaching up to 400 years, maintain functional eyesight well into old age without showing signs of retinal degeneration. According to a study published in Nature Communications and led by University of California, Irvine associate professor of physiology and biophysics Dorota Skowronska-Krawczyk, a DNA repair mechanism likely preserves the vision of these Arctic predators despite freezing waters and parasitic eye infections.
Challenging Assumptions About Greenland Shark Vision
For decades, marine biologists suspected that Greenland sharks were functionally blind. Their thick gray bodies, small heads, and cloudy-looking eyes often host parasites attached directly to the eyeballs. Combined with the pitch-black, murky environment of their deep Arctic habitat, these factors led researchers to believe the animals relied entirely on senses other than sight.
However, Dorota Skowronska-Krawczyk questioned that assumption after analyzing underwater footage. “After watching many videos, I realized this animal is moving its eyeball toward the light,” she states. That observation prompted a collaborative investigation into the visual systems of centuries-old sharks alongside researchers from the University of Basel, Switzerland, including Walter Salzburger and Lily G. Fogg, who examined the evolutionary aspects of the work.
Dissecting Centuries-Old Eyeballs
To test whether the sharks could actually see, researchers examined specimens caught between 2020 and 2024 using scientific long lines near the University of Copenhagen’s Arctic Station on Disko Island, Greenland. John Fleng Steffensen, a marine biology professor at the University of Copenhagen, partnered with Peter G. Bushnell of Indiana University South Bend and Richard W. Brill of the Virginia Institute of Marine Science to dissect and preserve the specimens.
Did you know? Emily Tom, a 28-year-old UC Irvine Ph.D. student and physician-scientist in training, recalls opening a package containing a preserved, baseball-sized eye from a 200-year-old shark sitting on dry ice. Working with tissue that large required careful thawing protocols to prevent sample deterioration in a lab that smelled, according to Tom, like a fish market.
No Signs of Retinal Cell Death
Emily Tom performed histological and vision-specific analyses on the preserved eye tissue under the guidance of Dorota Skowronska-Krawczyk. The team discovered zero evidence of cell death in the retina. Furthermore, tests confirmed that rhodopsin—a vital protein for dim-light vision—remained active within the shark’s retina and was specifically tuned to detect blue light.
This biological adaptation helps the animals navigate the faint blue light filtering deep beneath Arctic waters. According to the research team, the findings demonstrate that extreme longevity does not automatically trigger the severe retinal deterioration typically observed in aging animals.
Implications for Human Aging and Eye Diseases
Beyond marine biology, these discoveries offer potential pathways for understanding human ocular health. By studying how Greenland sharks maintain tissue functionality over centuries, researchers hope to gain insights that could eventually guide treatments for age-related eye diseases like macular degeneration and glaucoma.
Funding uncertainties continue to pose challenges for ongoing laboratory work, but Dorota Skowronska-Krawczyk expresses confidence in the future of the research. “What I love about my work is that we are the first in the world to see results—at the forefront, finding new mechanisms, rules and discoveries,” she says.
Frequently Asked Questions
How long do Greenland sharks live?
Greenland sharks are the longest-living vertebrates known to science, with individual specimens surviving for as long as 400 years, according to research cited by University of California, Irvine scientists.
Why did scientists think Greenland sharks were blind?
Researchers long suspected functional blindness due to the extremely dark Arctic environment and the presence of parasites frequently attached directly to the sharks’ cloudy eyeballs.
How do Greenland sharks see in the dark?
According to research published in Nature Communications, Greenland sharks retain active rhodopsin proteins tuned specifically to detect blue light, allowing them to utilize faint light levels in deep Arctic waters.
Can this research help human medicine?
Scientists note that understanding how these sharks preserve their eyesight over centuries could help guide future research into human age-related eye conditions such as glaucoma and macular degeneration.
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