Greenland Sharks Can Survive For Centuries In The Dark, And They Could Hold Clues To Preserving Human Vision

The longest-living vertebrates in the world are Greenland sharks. They live for up to 400 years deep down in the waters of the Arctic and the North Atlantic.

It was assumed that Greenland sharks have very poor vision due to eye parasites and spending their lives in the dimly lit depths of the ocean.

However, new research has found that the animals can actually see and maintain a functional visual system throughout their lifetimes.

The findings may have implications for human sight problems. Perhaps learning more about the sharks could prevent conditions like macular degeneration and glaucoma.

A team of researchers from the United States, Denmark, and Switzerland studied the eyes of 10 Greenland sharks that were caught off the coast of western Greenland and euthanized between 2020 and 2024.

The sharks were estimated to range in age from 100 to 134 years old.

The researchers found no signs of degeneration in the light-sensitive parts of the eyes, and the eye parasites didn't seem to affect the sharks' vision. Most vertebrates have two types of light-sensitive eye cells: cones and rods.

Cones help differentiate colors and work well in bright light, while rods do not detect colors and work well in dim light. The Greenland sharks had rod cells only, meaning they see things in black and white.

This adaptation is typical in animals that spend the majority of their lives in low-light conditions.

Nodi - stock.adobe.com - illustrative purposes only

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Greenland sharks live up to 3,940 feet below the surface, although they can dive deeper. The amount of sunlight that can penetrate through water that deep is virtually none.

"[As a Greenland shark,] you don't have high resolution," said Dorota Skowronska-Krawcyzk, a co-author of the study and a physiologist at the University of California, Irvine.

"You see light and darkness, but you don't really see the shapes very well, or you cannot distinguish probably fast movements."

After analyzing genetic material from some of the eyeballs more closely, the team realized that the genes ERCC1 and ERCC4 could be why the sharks' vision has lasted so long.

These genes are related to proteins that aid in repairing DNA. Sharks that have the ERCC1 gene live the longest lives. Furthermore, Greenland sharks had more ERCC4 genes compared to other sharks.

Overall, the results of the study suggest that Greenland sharks have adapted well enough to have permanent night vision in the darkness where they live.

These animals have helped highlight the great potential for maintaining visual function. There is much that scientists have to learn from the Greenland shark regarding vision.

"Our findings support the presence of a preserved and functional visual system in the adult Greenland shark, which seems well-adapted to extreme low-light conditions," wrote the researchers.

The study was published in the journal Nature Communications.