Inside the eyes of a 400-year-old shark

Scientists from Switzerland, the US and Denmark have described the visual system of the world’s longest-living vertebrate – the Greenland shark.

Writing in Nature Communications, researchers noted that the shark lives in the dark, cold waters of the arctic sea – and has an estimated lifespan of around 400 years.

The authors highlighted that it was previously thought that the Greenland shark had impaired vision due to a high prevalence of corneal parasitisation, its “extreme lifespan” and harsh environmental conditions. Greenland sharks live up to three kilometres below the ocean surface in temperatures as low as -1.1 degrees.

However, by examining the eyes of 10 deceased Greenland sharks between the ages of 100 and 134 years old, the researchers presented evidence that the visual system of the sharks remain intact.

The researchers highlighted that they found an absence of obvious retinal degeneration in “exceptionally old individuals.”

“These findings highlight the extraordinary adaptability of vertebrate sensory systems in extreme environments and the remarkable preservation of organ function over hundreds of years,” the authors shared.

The researchers suggested that the DNA-repairing genes, ERCC1 and ERCC4, might be related to a mechanism underpinning the long-term retinal health of the sharks.

Scientists from the University of Basel, University of California, the University of Copenhagen, Indiana University South Bend and Virginia Institute of Marine Science contributed to the research.