Greenland sharks are thought to live longer than any other vertebrate on Earth, with some individuals estimated at nearly 400 years old. That figure, first established in 2016 through radiocarbon dating of shark eye lenses, made the species the longest-lived vertebrate known to science, easily outlasting bowhead whales and giant tortoises. A study published this month in Nature Communications asks a follow-up question: after four centuries in the cold, dark water of the North Atlantic, why do the sharks' eyes still seem to work?
Researchers led by Dorota Skowronska-Krawczyk, a physiology and biophysics professor at the University of California, Irvine, examined eye tissue from sharks caught near Disko Island, Greenland, between 2020 and 2024, including one eyeball estimated at roughly 200 years old. Unlike the retinas of aging humans and most other animals, the shark tissue showed no evidence of retinal cell death. Rhodopsin, the light-sensitive protein that lets the retina detect faint light, remained active and tuned to the blue wavelengths that dominate in deep water.
The team traced the preserved vision to an active DNA repair system that appears to keep correcting cellular damage that would otherwise accumulate over centuries of exposure. Skowronska-Krawczyk described watching the tissue respond to light in the lab.
You see it move its eye. The shark is tracking the light — it's fascinating.
Dorota Skowronska-Krawczyk, University of California, Irvine
The project drew on a small international team, with co-authors from the University of Basel in Switzerland working alongside marine biologists from the University of Copenhagen, Indiana University South Bend and the Virginia Institute of Marine Science. The sharks studied were caught incidentally in fishing gear off Greenland rather than taken specifically for the research.
The findings, reported in Ophthalmology Times, are early-stage and specific to a slow-moving deep-sea fish, not a roadmap for treating human eyes. But researchers say related DNA repair pathways exist, in weaker form, in people, and studying how the sharks keep them running could eventually inform research into age-related conditions such as macular degeneration and glaucoma.
