Greenland sharks are the longest-living vertebrates known to science, with some individuals surviving for as long as 400 years. Despite their longevity, these sharks have thick gray bodies and small heads, and their cloudy-looking eyes can appear almost lifeless due to parasites often found attached directly to the eyeballs. However, new research led by Dorota Skowronska-Krawczyk from the University of California, Irvine suggests that Greenland sharks may not be functionally blind as previously thought.
The study, co-authored by researchers from the University of Basel and other institutions, challenges assumptions about Greenland shark vision while offering new clues about aging and longevity. The findings suggest that a DNA repair mechanism may allow Greenland sharks to preserve their eyesight for centuries without showing signs of retinal degeneration. Their visual systems also appear specially adapted to the extremely low light levels of their Arctic habitat.
Emily Tom, a UC Irvine Ph.D. student and physician-scientist in training, handled preserved eye tissue from the Greenland sharks with precision during her research. The researchers found no evidence of cell death in the retina and discovered that rhodopsin (a protein essential for vision in dim light) remained active in the shark retina. This adaptation could help Greenland sharks see in the faint light available deep beneath Arctic waters. The results suggest that the remarkable lifespan of these sharks does not necessarily come with severe retinal deterioration, raising possibilities for understanding age-related vision loss and guiding research into eye diseases like macular degeneration and glaucoma.