Published in Nature Communications, new research led by University of California, Irvine associate professor of physiology and biophysics Dorota Skowronska-Krawczyk reveals that 400-year-old Greenland sharks maintain active DNA repair mechanisms that preserve their eyesight, challenging long-held assumptions that these Arctic vertebrates are functionally blind.
Scaling Up to a 200-Year-Old Eyeball
Dorota Skowronska-Krawczyk first became interested in the species after reading a 2016 research paper published in the journal Science by John Fleng Steffensen, a professor of marine biology at the University of Copenhagen. Steffensen’s work noted that many Greenland sharks harbor parasites attached directly to their eyeballs. Combined with the pitch-black, murky depths of the Arctic waters they inhabit, scientists long assumed these creatures had written off their sense of sight entirely. Yet, video footage showing the sharks tracking light sources convinced Skowronska-Krawczyk to take a closer look.
Between 2020 and 2024, a team of marine researchers—including Steffensen, Peter G. Bushnell of Indiana University South Bend, and Richard W. Brill of the Virginia Institute of Marine Science—caught specimens using scientific long lines near the University of Copenhagen’s Arctic Station on Disko Island, Greenland. They dissected the sharks’ eyes and preserved them for laboratory analysis. Emily Tom, a UC Irvine Ph.D. student and physician-scientist in training within Skowronska-Krawczyk’s lab, recalled receiving the package containing the biological samples. “I opened the package, and there was a giant, 200-year-old eyeball sitting on dry ice just staring back at me,” Tom said. “We’re used to working with mouse eyeballs, which are the size of a papaya seed, so we had to figure out how to scale up to a baseball-sized eyeball.”
Cellular Resilience in the Arctic Depths
Working with baseball-sized ocular tissue required meticulous execution. Defrosting the samples had to be managed carefully to prevent tissue degradation, an operational challenge that left the laboratory redolent of a fish market. Once thawed, Tom performed histological and vision-specific analyses on the preserved eyes.
The results upended expectations of age-related cellular decay. Researchers found zero evidence of cell death in the retina. Furthermore, rhodopsin—a vital protein responsible for vision in dim environments—remained active within the shark retina. Evolutionary aspects of the work were co-authored by Walter Salzburger and Lily G. Fogg from the University of Basel in Switzerland. Their analysis indicates that the rhodopsin protein is specifically tuned to detect blue light, matching the sparse light penetration available in the Greenland shark’s deep-sea environment. According to the study findings, an active DNA repair mechanism likely shields the visual system from retinal degeneration, allowing the animals to retain functional eyesight across centuries.
Decoding Age-Related Diseases
The implications of the research extend far beyond marine biology. Skowronska-Krawczyk studies the molecular mechanics of age-related eye diseases to better comprehend how human vision degrades over time.
