He was considered a relic of the abyss, a near-blind giant navigating on instinct. THE Greenland shark, known for his record longevity which can exceed four centuries, has just revealed one of its most surprising secrets: its eyes work. And they work well.
An international team of researchers has demonstrated that, despite parasites and the almost total darkness of its habitat, this predator maintains functional vision throughout its life, calling into question decades of beliefs scientists.
How could his vision have been so underestimated?
For years, the scientific consensus was simple: the shark of Greenland did not need to see. Living until 3000 meters deep in the frigid waters of the Arctic, its environment is of almost total darkness. In addition, its eyes, the size of a baseball, are very often colonized by a small parasitic crustaceanOmmatokoita elongata, which attaches directly to the cornea, making it opaque.
These two factors, combined with his slow and opportunistic nature, seemed to confirm a progressive atrophy of his visual abilities. However, more careful observations showed that the animal followed light sources, a behavior completely incompatible with blindness. It was this paradox that prompted scientists to take a closer look at centuries-old eyeballs.
What unique adaptations protect its eyes?
Analysis of ocular tissues revealed a biological machinery perfectly adapted to its environment. There retina of the shark is dominated by rods, photoreceptors specialized in low light vision. These rods are not only longer and denser than standard, but they are also optimized to capture blue light, the only wavelength that penetrates the deep sea.
Even more astonishing, the eyes of specimens more than a century old showed no signs of degeneration. The key would lie in a powerful mechanism of DNA repairnotably involving the ERCC1 and ERCC4 genes. This system of cellular maintenance ultra-efficient would protect the cells of the retina from damage accumulated over hundreds of years, ensuring the robustness of its visual system.
What are the implications for human health?
This discovery goes far beyond the scope of the marine biology. Understand how a vertebrate can preserve its incredible longevity and the integrity of its vision opens fascinating perspectives for human medicine. THE degenerative diseases of the eye, such as age-related macular degeneration (AMD) or glaucoma, are directly linked to aging and the accumulation of cellular damage.
The study of the DNA repair system of the Greenland shark could therefore inspire new therapeutic strategies. The objective: to develop treatments capable of slowing down or even reversing the aging processes of the human retina. The secret of the eye youth may have been hiding in the icy depths of the Arctic.
Frequently Asked Questions (FAQ)
Does the parasite make the shark completely blind?
No. Transmittance measurements showed that despite the presence of the parasite, the shark’s cornea allows enough light to pass through, particularly in the blue spectrum, for the retina to capture it. Vision is probably impaired, but certainly not destroyed.
How old can the Greenland shark reach?
Studies based on radiocarbon dating of the lens of the eye have estimated that some individuals can live up to 400 ansor even more. This makes it the longest-lived vertebrate known on Earth.
