This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:
Because the Greenland shark lives in the dim depths of the ocean and is often infested with parasites that attach to its eyes, scientists believed the large, long-lived species to be functionally blind. But UC Irvine researcher Dorota Skowronska-Krawczyk and colleagues have disproved this, challenging what is known about aging, vision and longevity. Credit: Ghislain Bardout
Dorota Skowronska-Krawczyk sits in her office, eyes fixed on the computer monitor in front of her. "You see it move its eye," says the UC Irvine associate professor of physiology and biophysics, pointing to an image of a Greenland shark slowly drifting through the murky Arctic Ocean. "The shark is tracking the light—it's fascinating."
The video shows the longest-living vertebrate in the world—long, thick, gray body; small head; and short, rounded snout—with opaque eyes that appear lifeless, except for the parasite latched to one of its eyeballs. Scientists have long suspected the large species to be functionally blind, given the frequent presence of the parasite and its exceptionally dim and obstructed visual environment.
Now, new research from Skowronska-Krawczyk on Greenland shark vision—co-authored by University of Basel, Switzerland researchers Walter Salzburger and Lily G. Fogg, who worked on the evolutionary aspect of the study—is challenging what we know about aging, vision and longevity.
Published in Nature Communications, her findings suggest that a DNA repair mechanism enables these sharks—some of which live for 400 years—to maintain their vision over centuries with no signs of retinal degeneration and that they are well adapted to extreme low-light conditions.
Skowronska-Krawczyk, who gleans insights into the molecular mechanisms of aging by studying processes that control age-related eye diseases, attributes her interest in the visual system of the Greenland shark to a 2016 research paper by John Fleng Steffensen published in the journal Science.
"One of my takeaway conclusions from the Science paper was that many Greenland sharks have parasites attached to their eyes—which could impair their vision," she says. "Evolutionarily speaking, you don't keep the organ that you don't need. After watching many videos, I realized this animal was moving its eyeballs toward the light."
This left Skowronska-Krawczyk wanting to learn more.
The Greenland sharks used in her co-study were caught between 2020 and 2024 using scientific long lines off the coast of the University of Copenhagen's Arctic Station on Disko Island, Greenland. Steffensen, professor of marine biology at the University of Copenhagen, and colleagues Peter G. Bushnell, who teaches at Indiana University South Bend, and Richard W. Brill, who's based at the Virginia Institute of Marine Science, dissected and preserved the eyeballs in a fixative solution for examination.
... continue reading