Greenland Shark Visual System Maintains Integrity Over Centuries, Study Finds

New scientific findings, detailed in research finalized in late 2025 and published in Nature Communications, demonstrate that the Greenland shark, the longest-living vertebrate with a potential lifespan exceeding four centuries, maintains a remarkably functional and resilient visual system despite its extreme age.

This international investigation, spearheaded by researchers from the University of California, Irvine and other institutions, utilized advanced genomic sequencing and histological analysis on specimens retrieved near Disko Island, Greenland. The study confirmed that the shark’s visual apparatus is specifically optimized for the perpetual twilight of the deep sea, relying almost exclusively on rod cells in the retina to maximize the capture of scarce photons, prioritizing light detection over fine detail.

Crucially, histological examination of retinal tissue from sharks estimated to be over a century old revealed an unexpected absence of degeneration in key cellular layers, suggesting a near-stasis in biological aging within this tissue. This preservation is linked to the elevated expression of critical DNA repair genes, specifically citing ercc1 and ercc4, which appear to provide continuous maintenance against accumulated genetic damage over hundreds of years. Furthermore, retinal cell membranes are notably rich in very long-chain fatty acids, vital for maintaining the flexibility required for the light-capturing pigment, rhodopsin, to function effectively in near-freezing temperatures.

The research also directly addressed the long-held assumption that the copepod parasite Ommatokoita elongata renders the Greenland shark functionally blind. Scientists established that between 66% and 100% of blue light is still able to penetrate the cornea and reach the light-sensitive retina, effectively debunking the notion of complete visual incapacitation solely due to the parasite, although corneal tissue damage from the up to 30 mm long copepod is acknowledged. The shark's reliance on acute senses like smell is thought to mitigate any functional deficit caused by scarring.

The study's focus on eyes collected between 2020 and 2024 opens significant avenues for biomedical exploration into age-related human ocular conditions, including glaucoma and macular degeneration. Related research illuminates the shark's genetic context, noting that its genome shows a functionally connected network of duplicated genes enriched for DNA repair functions, which, alongside adaptations in immune regulation pathways like NF-κB signaling, contributes to its extended lifespan. Findings co-authored by specialists like Walter Salzburger and Lily G. Fogg underscore that the molecular mechanisms safeguarding retinal integrity over centuries present a profound model for understanding human senescence-related vision loss.