Amazing stuff!
"... the longest-living vertebrate in the world ... 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 ... on Greenland shark vision ... is challenging what we know about aging, vision and longevity. ...
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. ..."
From the abstract:
"The Greenland shark (Somniosus microcephalus) is the longest-living vertebrate and inhabits the exceptionally dim and cold waters of the Arctic deep sea. Due to its extreme lifespan, harsh environmental conditions, and prevalent corneal parasitisation, the Greenland shark has previously been thought to have impaired or degenerated vision.
Here, we present genomic, transcriptomic, histological and functional evidence that the Greenland shark retains an intact visual system well-adapted for life in dim light.
Histology and in vitro opsin expression revealed visual adaptations typical of deep-sea species, including densely packed, elongated rods and a short-wavelength shift in rod visual pigment sensitivity compared to shallow-water sharks. In situ hybridisation confirmed the presence of essential visual cell types: rods, Müller glia, and bipolar, amacrine, and ganglion cells.
Moreover, despite being over a century old, the examined specimens showed no obvious signs of retinal degeneration. Using whole genome and retinal RNA-sequencing, we further show that dim-light (rod-based) vision genes are intact and robustly expressed, while many bright-light (cone-based) vision genes have become pseudogenized and/or are no longer expressed.
Finally, we identify robust expression of DNA repair-associated genes in the retina, which may help support long-term maintenance of retinal integrity over the Greenland shark’s extreme lifespan."
Eye-opening research (original news release) "... astonishing findings about Greenland sharks may lead to new ways of preserving vision as we age"
The deep sea Greenland shark
Fig. 1: Visual system of the Greenland shark.
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