New research is challenging long-held beliefs about the eyesight of Greenland sharks, a species known for its extreme longevity and deep-sea habitat. A study led by UC Irvine associate professor Dorota Skowronska-Krawczyk reveals that these Greenland sharks possess a unique DNA repair process that protects their eyes from age-related damage, allowing them to retain functional vision over centuries.
The findings offer new insight into how vision can be preserved across a lifespan and may help inform treatments for human eye diseases.
The study, published in Nature Communications, was co-authored with evolutionary researchers Walter Salzburger and Lily G. Fogg from the University of Basel in Switzerland.
The team found that the sharks’ retinal tissue shows no signs of degeneration, even in individuals estimated to be around 200 years old. Rhodopsin, a protein critical for low-light vision, remained active and tuned to detect blue light, which dominates their Arctic environment.
Eye function preserved in the world’s longest-living vertebrate
Greenland sharks, often thought to be nearly blind due to parasites commonly attached to their eyes and the dim conditions in which they live, may have more visual capability than previously assumed.
Skowronska-Krawczyk first became interested in their vision after reading a 2016 study by marine biologist John Fleng Steffensen. She noted that the continued presence of functional eyes in a species would not make evolutionary sense unless those eyes served a purpose.
Her curiosity deepened after watching videos of the sharks, where she observed subtle eye movements in response to light. That led her to pursue a deeper investigation into how the species might preserve eye function over time.
Between 2020 and 2024, researchers collected specimens using scientific long lines near Disko Island in Greenland. Steffensen and his colleagues, Peter G. Bushnell of Indiana University South Bend and Richard W. Brill of the Virginia Institute of Marine Science, dissected the shark eyes and preserved them for further analysis.
How Greenland sharks use DNA repair to protect their vision
The samples were later studied at UC Irvine, where Skowronska-Krawczyk’s lab, including Ph.D. student Emily Tom, conducted histological and molecular tests. Tom said receiving a preserved eyeball from a 200-year-old shark was unlike anything she had experienced.
Used to working with mouse eyes, she noted the challenge of scaling up to the larger samples and ensuring the tissue remained intact during analysis.
Tom confirmed the absence of cell death and highlighted the importance of studying long-lived species like Greenland sharks to better understand the link between DNA repair, vision, and aging. Skowronska-Krawczyk believes these discoveries could lead to new approaches for treating conditions such as glaucoma and macular degeneration.
Despite concerns over limited federal research funding, she remains optimistic. For her, being part of the first team to uncover these mechanisms and passing that experience on to students is the most rewarding part of the work.
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