Greenland sharks are among the longest-lived vertebrates ever identified, with some individuals estimated to be centuries old. They live in some of the darkest waters on Earth, deep in the Arctic, where light is scarce and visibility is poor. Many of them also carry parasites attached to the surface of the eye, a detail that has contributed to the suggestion that vision plays a small role in their lives.
New research is challenging this view. Research published in Natural communications found that Greenland sharks retain functional vision even into old age, without signs of retinal degeneration typically associated with aging. The work suggests that these sharks are not only able to see in the dark, but are biologically equipped to maintain this ability for centuries.
Read more: Sharks began roaming the oceans 400 million years ago as deep-sea dwellers.
Shark Vision, made for the dark
To understand what's going on inside the eye, the researchers examined the preserved eyeballs of Greenland sharks caught between 2020 and 2024 near Disko Island off the coast of Greenland. The resulting samples allowed for detailed analysis of retinal tissue – a unique opportunity for animals that live for hundreds of years.
Even in sharks The age of the retina is estimated to be several centuries, but neither massive cell death nor structural destruction has been detected in it. Key cell layers remained intact, indicating that vision did not deteriorate with age in the same way as in most vertebrates.
The structure of the retina helps explain how such vision is possible. Instead of the usual mixture of rods and cones, Greenland sharks' retinas are made almost entirely of rods, densely packed photoreceptors that specialize in dim light. This configuration is typical of deep-sea species, for which capturing rare photons is more important than color or fine detail.
Other functions seem to be configured for the same task. Retinal cell membranes are rich in long-chain polyunsaturated fatty acids, which help rhodopsin, a light-sensitive pigment, function effectively in cold, low-light conditions. Corneal measurements also showed that enough light reaches the retina to stimulate vision even when parasites are attached to the surface of the eye.
Retina that doesn't wear out
The team also analyzed rhodopsin itself, a protein essential for vision in the dark. In the Greenland sharks, rhodopsin remained active and tuned to blue wavelengths, the type of light that penetrates deepest into Arctic waters. This setting assumes that sharksVisual systems are not only preserved, but also perfectly adapt to the environment.
At the molecular level, the results point to mechanisms that protect retinal cells from cumulative damage. Instead of slowing down the aging of the entire body, Greenland sharks Special repair and maintenance systems appear to be maintained that keep critical tissues functioning much longer than expected.
This distinction matters. Aging is often portrayed as an inevitable, uniform decline in population, but the Greenland shark points to a different model—one in which certain organs completely resist decay, even over centuries.
What a 400-year-old shark can tell us about aging
The study does not suggest that humans could achieve the same lifespan or directly adopt shark biology. But it raises questions about why age-related vision loss is so common and whether it should be.
By studying species that retain sensory functions for extraordinary periods of time, researchers can begin to separate aspects of aging that are truly inevitable from those that are shaped by long-term recovery and adaptation. In this sense, the Greenland shark is not so much a biological curiosity as it is an example of how aging does not always mean decline.
Read more: Rare and elusive CookieCutter shark leaves a circular wound on its prey
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