Owls are one of the few predators of bird animals that catch their prey at night, and new research suggests that the DNA molecules in their eyes are something special that gives them a powerful visual advantage in the dark.
Through natural selection, new research suggests that DNA in owl retinal cells may have been assembled to act as a kind of lens or vision enhancer, improving vision at night.
Birds have not previously seen an unusual trait, suggesting that owls have traveled it alone on this particular evolutionary path, at least among birds. Most birds are on days like we are – we are most active during the day and sleep everything at night.
“Traces of positive selection for visual detection, particularly in the evolution of genes functionally related to phototransduction and chromosome packaging, were found in the ancestral branch of owls,” the researchers write in their paper.
The group looked at the genomes of 20 different bird species, including 11 owls, and identified a positive choice – where beneficial mutations had been kept for generations. As expected, much of this has happened in areas of sensory perception, which is why owls hear and see so well.
But the group also found signs of accelerated evolution from 32 genes that were more of a surprise. These genes were combined into DNA packaging and chromosome condensation – as if the structure of the molecules inside the owl eyes had themselves adapted to be able to capture more light.
A similar change in the DNA molecular arrangement of retinal cells has been seen in nocturnal primates in the past, and computer models of their molecular structure have suggested that they can channel light.
This isn’t the only evolution that owls have to peek through the darkness – they also have retinas full of rod cells for better night vision, but it would certainly help get prey after dark.
While the researchers ’claims are still hypothetical, it is a fascinating idea. The comparison of genomes also supports the idea that owls did indeed evolve from day-old ancestors – because the biggest changes observed in their genetics seem to be related to improving nocturnal hunting abilities.
While the owls kept sharp pieces that they shared with birds of prey hunting during the day, such as eagles and hawks, the researchers found genes that differed from the owls ’ancestors and that could improve their excellent hearing, night vision, and soft feathers for silence in flight. If the results of the study are confirmed, even DNA molecules seem to increase the excellent vision of owls.
The authors warn that their proposed roles for different genes are currently only suggestions, especially about how owl eye photoreceptors actually work. Direct observations and analyzes may be able to build on the findings presented here, and they could tell us even more about how owls gained evolutionary benefits.
“Our research suggests new candidate genes whose role in owl evolution can be further explored,” the researchers write.
The study has been published Genomic biology and evolution.