How the Greenland shark could help humans fight glaucoma

For years, we've imagined it as a slow, almost blind giant, trudging through the dark waters of the Arctic. The Greenland shark, one of the longest-living vertebrates on the planet, seems like the perfect symbol of a life that goes on despite everything, even without really seeing the world around it.

Well, once again, science is forcing us to reconsider our certainties. In the depths where the Greenland shark lives, light is scarce, if not non-existent. To complicate matters, a parasite attaches itself to its eyes, making them opaque and seemingly useless. This is why, for decades, it was taken for granted that sight was a superfluous sense, of little use in such an extreme environment.

It was Dorota Skowronska-Krawczyk, Professor of Physiology and Biophysics at the University of California, Irvine, who completely overturned this theory. After several viewings of underwater images, one detail didn't add up: the shark was moving its eyes as it followed the light. This was not a random reflex, but a genuine visual behavior. This was the starting point for research, which is now the subject of much debate in the scientific community.

Hundreds of years old eyes and no sign of degeneration

The study, published in Nature Communications and conducted in collaboration with the University of Basel, focused on the eyes of sharks caught between 2020 and 2024 off Greenland. Some of these animals were estimated to be over 200 years old, while others could have lived to be almost 400.

Even when examining the eye tissue under a microscope, researchers found no evidence of retinal degeneration. The cells were intact, active and functional. This is a surprising result, especially when compared with humans, whose vision tends to deteriorate after only a few decades.

The key seems to be a particularly efficient DNA repair mechanism. In practice, the Greenland shark manages to 'repair' cellular damage before it accumulates, enabling it to maintain healthy eyes for centuries. Even rhodopsin, the light-sensitive protein that enables us to see in low-light conditions, is fully functional and specialized in capturing blue light, the only light that can penetrate deep into the ocean.

From shark to man

Emily Tom, a PhD student in Skowronska-Krawczyk's team, came across an eyeball the size of a baseball, that belonged to a two-century-old shark. Despite its age, the tissue was surprisingly 'young'.

This is where the story of the Greenland shark ceases to be a mere zoological curiosity and becomes something that concerns us. Understanding how this animal manages to retain its sight for so long could offer new avenues for combating age-related eye diseases such as macular degeneration and glaucoma. Studying those who age slowly and well is one of the most effective ways of understanding what's wrong with our bodies.

For years, it was thought that, in extreme environments, evolution would push forward to eliminate what was unnecessary. This research suggests the opposite: even where light is dim, sight can remain a fundamental sense.

The Greenland shark, a silent inhabitant of the abyss, reminds us that nature finds solutions that we often don't imagine. And that, perhaps, to understand how to age better, we should take a greater interest in those who live longer than we do.

Source : Nature

(MP/©GreenMe.it/Translation and adaptation: The Global NaturePic: Unsplash)