Greenland Shark Vision Remains Intact Across Centuries of Extreme Longevity

A recent scientific investigation has detailed the sustained visual acuity of the Greenland shark (*Somniosus microcephalus*), the longest-living vertebrate known, challenging previous assumptions that advanced age and corneal parasites might render the deep-sea species functionally blind. The comprehensive study, published in the journal Nature Communications, analyzed ocular tissues from multiple Greenland sharks, with age estimates for several specimens surpassing one hundred years.

Researchers concentrated on the molecular and cellular integrity of the retina, focusing on its structure, which is essential for vision in low-light conditions. The analysis confirmed that the Greenland shark's retina is exclusively rod-dominated, an evolutionary adaptation suited for capturing the minimal, faint blue light penetrating its abyssal habitat hundreds of meters below the surface. Further molecular characterization established that rhodopsin, the critical light-sensing photopigment, is precisely tuned to a peak absorption wavelength of 458 nanometers, optimizing photon capture efficiency in the deep ocean environment.

Critically, subsequent molecular pathology tests on the oldest specimens revealed no evidence of progressive retinal degeneration or substantial photoreceptor cell death, indicating an exceptional level of biological maintenance across centuries. Scientists attribute this robust preservation to highly efficient DNA repair mechanisms operating within the retinal cells, which counteract the cumulative molecular damage associated with extreme longevity. The species is known to inhabit depths down to 2,200 meters in the North Atlantic and Arctic Oceans, where its rod-dominated vision is necessary for navigation and locating prey such as fish and seals.

The research team, which included scientists from institutions such as the University of Copenhagen, utilized radiocarbon dating on the sharks' eye lenses to confirm ages potentially reaching 392 years, solidifying their status as the longest-living vertebrates. This sustained visual performance in the face of extreme age provides a compelling natural model for understanding biological aging processes. The molecular stability observed in the rhodopsin and retinal structure suggests a superior cellular maintenance system that effectively prevents the accumulation of molecular degradation that typically compromises vision in older organisms, offering potential avenues for research into age-related human ocular pathologies.