A doctoral student at the University of California, Irvine, opened a shipping box and found a baseball-sized eyeball on dry ice, from a Greenland shark caught in Arctic water off Disko Island.<\/p>\n
What her lab found inside upends a long-standing assumption. Greenland sharks are the longest-lived vertebrates known, with lifespan estimates reaching 400 years. Their eyes look clouded, and parasitic copepods frequently attach to the cornea<\/a>. Scientists reasonably concluded the animals were functionally blind.<\/p>\n They are not. The preserved tissue retained a functional visual system, and retinas from specimens estimated to be more than a century old showed no obvious degeneration<\/a>.<\/p>\n The findings were published in Nature Communications<\/a> in January by a team led by UC Irvine’s Dorota Skowronska-Krawczyk, with evolutionary analysis from Lily G. Fogg and Walter Salzburger at Basel. Coverage resurfaced this month; the paper is not new.<\/p>\n Baseball-Sized Eyeballs Arrived on Dry Ice at a California Lab<\/p>\n The specimens were caught between 2020 and 2024 on scientific longlines near the University of Copenhagen’s Arctic Station in Greenland. John Fleng Steffensen of Copenhagen, Peter G. Bushnell of Indiana University South Bend, and Richard W. Brill of the Virginia Institute of Marine Science dissected and preserved the eyes.<\/p>\n Skowronska-Krawczyk’s interest began with a 2016 Science paper that used radiocarbon dating of eye-lens nuclei<\/a> to establish the species’ lifespan. That study put its largest animal at roughly 392 years, give or take 120, and estimated sexual maturity at about 156.<\/p>\n She kept watching a video of live sharks and noticed something that did not fit. “You see it move its eye,” she said in a UC Irvine feature<\/a>. “The shark is tracking the light.”<\/p>\n Her reasoning was evolutionary before it was experimental: animals do not maintain organs they no longer use. Cave fish in permanent darkness have degenerated retinas and broken vision genes. If this shark had lost sight, its eye would show it.<\/p>\n Rod Only Retinas Built for Water Almost Nothing Reaches<\/p>\n The tissue told a different story. Doctoral student Emily Tom ran the histology and vision analyses and found no evidence of cell death.<\/p>\n The architecture matched a deep-sea specialist, not a failing organ. The retinas were built entirely from rods, the photoreceptors used in dim light, elongated and densely packed. Cone genes, which encode opsins for color vision, were largely lost or pseudogenized.<\/p>\n Rhodopsin, the pigment behind low-light vision, remained active and peaked at 458 nanometers, a shift toward blue, the color that penetrates furthest into deep water. These animals live near-1\u00b0C at depths approaching 3,000 meters.<\/p>\n The team also tested whether parasitized corneas block light. Six shark corneas transmitted 70 to 100 percent of incoming light, against 95 percent for human donor corneas. The parasites are real, and the light still gets through.<\/p>\n DNA Repair Is a Hypothesis, Not a Demonstrated Mechanism<\/p>\n A line repeated across coverage holds that DNA repair keeps the shark’s eyes healthy for centuries. That overstates what was shown.<\/p>\n Genome and retinal RNA sequencing revealed that DNA repair genes were actively expressed, with elevated ercc4 expression compared with other sharks. The authors state that this may help support the long-term maintenance of retinal integrity. That is an inference from gene expression, not a demonstrated mechanism.<\/p>\n Sample size also constrains the work. Greenland sharks are hard to obtain and impossible to study experimentally, and several analyses rest on tissue from a single animal. The oldest specimen examined was estimated to exceed 130 years old for a vertebrate but well short of the 400-year headline figure.<\/p>\n What This Does Not Mean for Human Macular Degeneration<\/p>\n The connection Skowronska-Krawczyk is reaching toward is real but distant. Understanding how a retina stays functional for a century might eventually inform research into macular degeneration and glaucoma, leading causes of vision loss in older adults.<\/p>\n Between that hope and a treatment sits everything. No human cells were studied, no intervention was tested, and nothing here suggests a supplement, a therapy or a screening test.<\/p>\n Sharks are cartilaginous fish separated from humans by hundreds of millions of years of evolution, living in environments with temperatures and pressures that dramatically slow metabolism. The authors note that cold-water metabolic effects may attenuate cellular decline. A mechanism that works in near-freezing water may not transfer to a warm-blooded animal at all.<\/p>\n The researchers’ own framing is the honest one. Extreme longevity need not mean sensory decline. Systematic studies of retinal aging in other long-lived species are scarce, though turtles and tortoises show slow or negligible <\/a>senescence <\/a>by other measures. That opens a research question rather than answering a clinical one. Anyone worried about changes in their own vision should see an eye care professional, not a marine biologist.<\/p>\n Key Questions Answered<\/p>\n Were the sharks studied actually 400 years old?<\/p>\n No. The 400-year figure is the estimated maximum lifespan for the species. The specimens examined here were estimated at more than a century old, with the oldest exceeding 130 years.<\/p>\n What did the researchers actually find in the eyes?<\/p>\n An intact rod-only retina with active rhodopsin tuned to blue light, all major retinal cell types present, corneas that still transmit light despite parasites, and no obvious signs of degeneration.<\/p>\n Does this prove DNA repair keeps their vision intact?<\/p>\n No. DNA repair genes were expressed in the retina, which led the authors to suggest that repair may contribute. The mechanism was not demonstrated.<\/p>\n Could this lead to a treatment for macular degeneration?<\/p>\n Not in the near term. This is animal research with no human cells, no intervention, and no clinical endpoint. It identifies a question worth pursuing.<\/p>\n Why did scientists think these sharks were blind?<\/p>\n Their eyes appear clouded; they live in near-total darkness, and parasitic copepods commonly attach to the cornea, which is assumed to obstruct vision.<\/p>\n Is this new research?<\/p>\n The paper appeared in Nature Communications in January. Coverage resurfaced in August, but the underlying findings are several months old.<\/p>\n","protected":false},"excerpt":{"rendered":"A doctoral student at the University of California, Irvine, opened a shipping box and found a baseball-sized eyeball…\n","protected":false},"author":2,"featured_media":151910,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[5],"tags":[71564,66851,57,4349,71563,71562,71559,71561,71560],"class_list":["post-151909","post","type-post","status-publish","format-standard","has-post-thumbnail","category-greenland","tag-deep-sea","tag-dna-repair","tag-greenland","tag-greenland-shark","tag-longevity-research","tag-macular-degeneration","tag-retinal-degeneration","tag-rhodopsin","tag-vision-aging"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@dk\/117154276174905550","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts\/151909","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/comments?post=151909"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/posts\/151909\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/media\/151910"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/media?parent=151909"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/categories?post=151909"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/dk\/wp-json\/wp\/v2\/tags?post=151909"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}