For years, scientists thought Greenland sharks were basically blind. These deep-sea creatures live in the freezing dark waters of the Arctic and often have parasites clinging to their eyes, so it seemed obvious that their vision was pretty much gone. But a new study from researchers at the University of California, Irvine, says that assumption was wrong. It turns out these sharks, which can live for hundreds of years, may actually see just fine well into old age. The discovery is giving scientists fresh ideas about how human eyes age too, and whether something learned from a giant shark eyeball could eventually help with age-related vision problems in people.
The shark that keeps moving its eye toward the light
Dorota Skowronska-Krawczyk, an associate professor at UC Irvine, first got curious about this after watching video footage of a Greenland shark drifting through dark Arctic water. What caught her attention wasn’t the size of the animal or its incredible age, it was the eye. She noticed the shark tracking the light with its eyeball, something you wouldn’t expect from an animal thought to be blind. As she explained in a statement shared by UC Irvine, watching the shark actively follow the light made her want to learn more about what was really going on with its vision.
Why everyone assumed these sharks could not see
Greenland sharks are the longest-living vertebrates known to science, with some individuals surviving up to 400 years. Their thick grey bodies, small heads and rounded snouts are already unusual, but their eyes have long puzzled researchers too. Many appear cloudy and lifeless, and a parasite is often found dangling from the cornea. Combined with the pitch-dark environment they live in, this led scientists to suspect the sharks were functionally blind for a long time.
Studying a 200-year-old eyeball in the lab
Getting hold of shark eye tissue for this kind of work is not easy. Between 2020 and 2024, Greenland sharks were collected near Disko Island in Greenland, and the eyes were preserved before being sent to Skowronska-Krawczyk’s lab for analysis. Emily Tom, a PhD student and physician scientist in training in the lab, was used to handling mouse eyes and remembers opening the package to find a baseball-sized, two 100-year-old eyeballs staring back at her. Using histological analysis, she examined the tissue and found no evidence of cell death in the retina. Even more surprising, a protein called rhodopsin, which is essential for seeing in dim light, was fully functional and tuned to detect blue light, the kind of light that travels furthest underwater.
A DNA repair process that may protect against ageing
The full findings have been published in the paper The visual system of the longest living vertebrate, the Greenland shark in Nature Communications, co-authored with University of Basel researchers Walter Salzburger and Lily G Fogg, who worked on the evolutionary side of the project. The study points to a DNA repair mechanism that appears to protect the shark retina from the kind of damage that usually builds up with age. This matters because in humans, the eye is often one of the first places where age-related decline shows up, leading to conditions like macular degeneration and glaucoma. If a Greenland shark can keep its retina in near-perfect shape for centuries, understanding how it manages that could open up new directions for treating vision loss in people as they grow older.
What this could mean for future research
Skowronska-Krawczyk believes the value of this work goes well beyond shark biology. Long-lived animals like the Greenland shark offer a rare natural experiment in how tissues resist the effects of ageing over extremely long timescales, and studying them could reshape how scientists think about vision, cellular repair and longevity in general. She has said that not many researchers work on shark vision specifically, which is part of what makes this discovery so valuable. For now, this slow-moving Arctic shark and its strangely durable eyes may end up teaching us something important about our own. Go to Source
