A recent study published in Nature Communications found that the Greenland shark (Somniosus microcephalus), known for its lifespan of up to 400 years, possesses fully functional eyes that show minimal deterioration even after a century. Previously, it was believed their eyes were barely functional due to their deep-sea habitat and the presence of parasitic crustaceans.
Key Findings on Shark Eye Function
- Researchers examined eyes from 10 deceased Greenland sharks, estimated to be between 100 and 134 years old.
- Greenland shark eyes, measuring 5–6 centimeters in diameter, contain only rod cells, which are optimized for dim light vision, meaning they perceive their environment in black and white with limited resolution.
- Despite parasitic copepods (Ommatokoita elongata) attaching to their corneas, the sharks' ability to detect light, contrast, and movement is not significantly hindered.
- A notable observation was the pristine condition and lack of degeneration in the retinas of the studied eyes.
Implications for Human Eye Health
The study suggests that specific DNA repair genes, ERCC1 and ERCC4, may contribute to the long-term health of the shark's retina. Lead study author Lily Fogg and senior author Dorota Skowronska-Krawczyk indicate that understanding this mechanism could have biomedical applications for humans.
Visual neuroscientist Patricia Jusuf noted that the same genes are involved in human DNA repair pathways. Malfunctions in these genes in mammals are linked to premature aging. The absence of retinal degeneration in aged Greenland sharks suggests these DNA repair pathways could be crucial for maintaining retinal health and vision throughout a long lifespan.
This research offers promising avenues for counteracting age-related retinal degeneration, macular degeneration, and retinitis pigmentosa in humans, conditions that affect over 200 million people globally. Further investigation into these DNA repair mechanisms could lead to genetic or molecular therapies.
Future Research
The findings underscore the potential for bio-inspired approaches from nature to address human health challenges. Researchers are also considering studying other "sleeper shark" species, such as the southern sleeper shark (Somniosus antarcticus) and Pacific sleeper shark (Somniosus pacificus) found in waters around Australia and New Zealand, for additional genetic insights that could benefit humans.