Greenland Shark Visual System Maintains Integrity Through DNA Repair Mechanisms

The Greenland shark (Somniosus microcephalus), a vertebrate with a potential lifespan exceeding 400 years, has long been associated with impaired vision due to deep-sea conditions and common eye parasites. However, recent research published in the journal Nature Communications in late 2025 has challenged this perception, revealing that their visual system remains fully functional and highly adapted to counteract cellular aging. An international research team, including contributors from the University of California, Irvine, utilized advanced genomic and histological techniques on samples collected near Disko Island, Greenland, between 2020 and 2024.

The study confirmed that this ancient shark maintains an intact visual system specifically optimized for the extreme darkness of its habitat. They rely heavily on rod cells in the retina to maximize the capture of scarce light, a common adaptation among deep-sea species. Histological examination of specimens over one hundred years old showed no evidence of retinal layer degeneration, a finding that contrasts sharply with the tissue damage typically accompanying aging in most vertebrates. Furthermore, they retain the tapetum lucidum, a reflective layer behind the retina that enhances the ability to capture stray photons of light.

The key to this remarkable capability lies in the highly elevated expression of DNA repair genes, such as ercc1 and ercc4, which function as a constant maintenance system against accumulated genetic damage over centuries. Previous genomic research, which published the Greenland shark’s genome in 2024, had already highlighted unique genetic adaptations for longevity. Maintaining retinal integrity across such an extreme timescale is critical, and this robust DNA repair mechanism is posited as the primary support structure.

Another adaptive aspect is the composition of the retinal cell membranes, which are rich in very long-chain polyunsaturated fatty acids (VLC-PUFAs). These lipids are essential for maintaining cell membrane flexibility, which allows for the effective function of the rhodopsin pigment in capturing light at the near-freezing temperatures of their habitat. VLC-PUFAs have been linked to counteracting the membrane stiffening induced by cold temperatures, supporting optimal visual performance in the Arctic environment.

The research also definitively addressed the common belief that the parasite Ommatokoita elongata causes blindness in the sharks. Scientists measured light transmission through infected corneas and found that the parasite still permitted 66% to 100% of blue light—the type that penetrates deepest in Arctic waters—to reach the retina. While the parasite can cause corneal ulceration and damage, these findings suggest sufficient light still reaches the retina to stimulate vision. Observations by researcher Dr. Dorota Skowronska-Krawczyk of UC Irvine, noting the sharks’ eye movements tracking light, further support that vision remains behaviorally relevant.

These comprehensive findings, based on the examination of centuries-old eyes, open new avenues for medical research. A deeper understanding of how the Greenland shark maintains ocular integrity over centuries could inspire the development of novel therapies to address age-related human eye conditions, such as glaucoma and macular degeneration. The shark’s ability to sustain vital organ function in extreme environments offers a profound perspective on biological resilience and cellular repair engineering.