Greenland shark study finds retinal tissue preserved despite extreme age
Researchers examining Greenland shark eyes found no evidence of retinal cell death and detected active rhodopsin adapted to blue light in low-light Arctic waters. The findings, reported in Nature Communications, challenge the assumption that the long-lived sharks are functionally blind and identify possible avenues for studying how vision is maintained with age.
The story
A research team led by Dorota Skowronska-Krawczyk of the University of California, Irvine examined eye tissue from Greenland sharks, a species reported to include individuals that can live as long as 400 years. The sharks had been caught for scientific study between 2020 and 2024 near the University of Copenhagen’s Arctic Station on Disko Island, Greenland, and their eyes were preserved for later analysis. Using histological and vision-specific analyses, the researchers reported no evidence of retinal cell death in the tissue they examined. They also found that rhodopsin, a light-sensitive protein needed for dim-light vision, remained active in the retina. The protein was tuned to blue light, consistent with the faint light available in deep Arctic water. The results counter a long-standing assumption that Greenland sharks may be functionally blind. Their eyes can appear cloudy, and parasites are often attached to their eyeballs; together with their dark, murky habitat, those observations had supported doubts about their vision. Videos showing the animals moving their eyes toward light helped prompt the investigation. The authors say their findings suggest that the sharks’ long lives do not necessarily involve the level of retinal degeneration that might be expected in very old animals.
Why it matters
Age-related retinal decline is a central concern in human vision research, including work on macular degeneration and glaucoma. Greenland sharks provide an unusual natural comparison because their lifespan greatly exceeds that of most vertebrates while their examined retinal tissue did not show the cell death reported in the study. Identifying the biological processes behind that preservation could sharpen basic research questions about how retinal cells withstand damage and retain function. It does not establish that the same mechanisms operate in people, but it supplies a long-lived animal system in which those possibilities can be investigated.
Evidence and context
Greenland sharks live in Arctic waters where available light is limited, making the study’s rhodopsin result relevant both to aging research and to sensory adaptation. Rhodopsin is essential for seeing in dim conditions; the researchers found the shark protein tuned to blue light, which can be useful in the species’ underwater environment. The study also links its observations to a possible DNA-repair mechanism, although the supplied report presents that as a suggested explanation rather than a demonstrated route to human therapies. The international author group included researchers connected with UC Irvine, the University of Basel, the University of Copenhagen, Indiana University South Bend and the Virginia Institute of Marine Science. The paper was published in Nature Communications.
Limits and unknowns
The conclusion is based on preserved eye samples and tissue analyses, not on direct behavioural tests that quantify how well individual Greenland sharks see in their habitat. Finding no retinal cell death in the examined tissue does not by itself establish normal visual acuity, nor does active rhodopsin prove the full extent of functional vision. Parasites attached to shark eyes could still impair sight in some animals. The report also describes DNA repair as a possible mechanism for long-term retinal preservation, so further work would be needed to identify the mechanism, test its effects and determine whether any aspect is relevant to human retinal disease.
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Scientific collection period
Greenland sharks examined in the study were caught with scientific long lines near Disko Island, Greenland, and their eyes were preserved for later analysis.
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Greenland shark study finds retinal tissue preserved despite extreme age
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Highlights
- Retinal cells preserved in ancient Greenland sharks
- Rhodopsin tuned to blue light aids vision in low-light waters
- New evidence counters belief that sharks are blind
- Insights may help combat human retinal degeneration
Transcript
Researchers found Greenland sharks’ retinal cells remain intact even after hundreds of years underwater.
Active rhodopsin protein in their eyes adapts to blue light in deep, dim Arctic environments.
This challenges the idea that Greenland sharks are functionally blind despite cloudy eyes and parasites.
Scientists hope to learn how these sharks avoid retinal cell death, informing human eye disease research.
Their unique biology offers a model to study aging vision and potential DNA repair mechanisms.