Greenland sharks are the longest-living vertebrates in the world with lifespans that can reach as much as 400 years, and a look into their dead eyes might suggest that they cannot see. Researchers have long suspected that these animals are functionally blind, particularly because they often have parasites latched onto their eyeballs, and they live in a very dim environment where the water is murky and their vision may often be obstructed. Now, scientists have published a study in Nature Communications that is changing what we thought we knew about these sharks and their visual abilities.
This work has suggested that there is a DNA repair process that allows these sharks to maintain the ability to see for centuries, and with no indication of degradation in their retinas. These sharks seem to be particularly well adapted to life in low-light conditions.
Researcher Dorota Skowronska-Krawczyk is a UC Irvine associate professor of physiology and biophysics, and has long been studying aging through the lens of age-related eye disorders. Skowronska-Krawczyk read a 2016 Science paper that noted the frequent presence of parasites on the eyes of Greenland sharks.
"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," said Skowronska-Krawczyk. "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.”
For this study, researchers studied preserved eyeballs from a few Greenland sharks that were captured in recent years.
Although this work may not seem to be relevant to humans, the findings could help us find new ways to prevent or treat age-related eye disorders like glaucoma. We can also learn more about basic biology, evolution, and health, which could have future applications that we cannot predict right now.
"What I love about my work is that we are the first in the world to see results; at the forefront, finding new mechanisms, rules and discoveries," added Skowronska-Krawczyk. "Then, being able to share this joy with students—that's the best part of it."
Sources: University of California, Irvine; Nature Communications
