The Longevity Secret Hiding in a Shark's Eyeball

Key takeaways

• Greenland sharks, the longest-living vertebrates, can survive as long as 400 years, and researchers just examined what their eyes look like over that timescale.
• In eye tissue from sharks estimated to be around 200 years old, scientists found no evidence of retinal cell death and active, functioning vision proteins, despite centuries of use.
• The team points to DNA repair as a likely reason these eyes hold up so well, offering a rare, real-world example of tissue that seems to resist the usual pace of age-related wear.

An eye built to outlast centuries

Greenland sharks live in the cold, dark waters of the Arctic, moving slowly and aging even more slowly. Some individuals are thought to reach 400 years old, making them the longest-living vertebrates identified so far. That kind of lifespan raises an obvious question for anyone interested in aging biology: if an animal's body holds up for four centuries, what does that actually look like at the tissue level?

A research team, including scientists from UC Irvine, the University of Copenhagen, and the University of Basel, set out to answer that question by focusing on one specific tissue: the eye. Vision-related tissue is often one of the more fragile, closely watched indicators of aging in animals and in people, which made it a useful lens (literally) for studying whether centuries of life leave the expected marks.

What centuries-old eye tissue actually revealed

Researchers analyzed eye tissue from Greenland sharks near Greenland's Disko Island between 2020 and 2024 — work that required precise handling since even brief warming could cause the tissue to start breaking down. One eye examined belonged to a shark estimated to be roughly 200 years old, and remarkably, it looked far from what you'd expect from that kind of age.

The retina showed no evidence of cell death. Rhodopsin, the protein responsible for enabling vision in low light, was still active and functioning. It was also finely tuned to detect blue light, the specific wavelength that filters down into the deep, dim Arctic water where these sharks spend their lives. Researchers even captured video of a shark moving its eye toward a light source and tracking it — a small but telling sign that vision was still doing its job.

Rewriting the "half-blind shark" assumption

For years, Greenland sharks have had a reputation for having poor eyesight. Their eyes often look cloudy, and it's common to see parasites attached directly to the eyeball, giving the impression of animals that simply don't rely on sight anymore. This study pushes back on that assumption. Healthy retinal tissue and active visual proteins suggest these sharks are seeing far more than their cloudy appearance implies, and doing so after centuries of life.

That distinction matters for how we think about tissue aging generally. An organ can look worn on the outside while still functioning well on the inside — and the reverse assumption, that visible wear always signals functional decline, doesn't hold up under closer examination here.

What might be behind the resilience

The researchers point to DNA repair as a likely piece of the explanation. Cells accumulate damage to their genetic material over time simply through everyday use, and how efficiently that damage gets repaired is one of the more consistently studied threads in aging biology across species. A visual system that keeps working smoothly for two centuries suggests unusually effective repair and maintenance processes at the cellular level, something researchers are now interested in understanding in more detail.

It's also a useful reminder that extreme longevity in nature rarely comes from one single trick. It tends to show up as a combination of slow metabolism, a stable cold environment, and cellular maintenance systems that simply don't let damage pile up the way it does in shorter-lived animals.

The takeaway

Nobody's suggesting a direct fix for human eyesight will come out of shark biology anytime soon. But animals that dramatically outlive typical aging timelines are one of the more genuinely useful natural experiments longevity researchers have access to. If a 200-year-old eye can still track light and show no sign of cell death, it's a strong hint that the ceiling on tissue maintenance is much higher than most biology assumes — and that studying how nature already solved this problem may be a faster path forward than trying to engineer a solution from scratch.

References:

Lily G. Fogg, Emily Tom, Maxime Policarpo, William Cho, Fangyuan Gao, Doreen Hii, Aaron E. Fawcett, Nicolas Boileau, Amalie Bech-Poulsen, Kirstine F. Steffensen, Cherlyn J. Ng, Peter G. Bushnell, John Fleng Steffensen, Richard Brill, Walter Salzburger, Dorota Skowronska-Krawczyk. The visual system of the longest-living vertebrate, the Greenland shark. Nature Communications, 2026; 17 (1). DOI: 10.1038/s41467-025-67429-6