Greenland sharks are considered the longest-lived vertebrates in the world: some species live for up to 400 years. For a long time, researchers suspected that these animals were blind, due to the constant presence of a parasite attached to their eyeballs and the dark environment in which they live. But a new study challenges that theory.
Published on January 5th in the scientific journal, the research suggests that a DNA repair mechanism allows them to maintain their vision intact over the centuries, without signs of retinal degeneration. Furthermore, the study indicates that these animals are well adapted to extreme low-light conditions.
“Not many people are studying sharks, especially their vision,” says Emily Tom, a physician-scientist in training who was involved in the research, in a press release. “We can learn a lot about vision and longevity from long-lived species like the Greenland shark, so having funding for research like this is really important.”
To carry out the study, researchers analyzed Greenland sharks caught between 2020 and 2024 with scientific fishing lines off the coast of the University of Copenhagen’s Arctic Station on Disko Island, Greenland. They dissected and preserved the eyeballs in a fixative solution for examination. According to the authors, the eyeball of these animals is similar in size to a baseball.
In the analysis, no signs of cell death were found and a protein called rhodopsin, essential for vision in low light, was found active in the sharks’ retinas and tuned to detect blue light.
For Skowronska-Krawczyk, leader of the study, the findings could have implications for human health, paving the way for new approaches to combating and eradicating eye diseases such as macular degeneration and glaucoma.
Furthermore, the research results may raise new questions about how vision evolves and better understand the mechanisms that help keep tissues alive and healthy for many years.
