Owls are one of the few avian predators that prey by night thanks to their eyes that are capable of night vision. But having a nocturnal predatory lifestyle is not easy as it comes with so many challenges.
Due to evolution, these birds have evolved several features that help them live the nightlife, such as their sharp talons and their nocturnal adaptations like the enhanced hearing and eyes that are capable of seeing clearly at night.
Recent research revealed that there is something unique in the DNA of an owl's eyes that is packaged, which gives them a visual advantage in the dark.
Natural Selection Developed a Unique Night Vision in Owls
In an article published in the journal Genome Biology and Evolution, the researchers led by Pamela Espíndola-Hernández, a doctoral student at the Max Planck Institute for Ornithology, said that DNA in the retinal cells of the owls is packaged together in a way that enhances the vision to improve eyesight during the night, Science Alert reported.
Scientists believed that owls might have diverged from their sister group Coraciimorphs, like the woodpeckers and kingfishers, during the Paleocene era when some small mammals may have led to greater availability of nocturnal prey.
It was assumed that owls developed nocturnal traits to adapt to nightlife and take advantage of the nightly feast. This began the selection of features that make them uniquely suited for a nocturnal life, which includes rod-rich retinas, asymmetrical ears, facial discs for enhanced hearing, and soft feathers for a silent flight.
Unique DNA Packaged in Owl Eyes
According to a report by WFMJ, the researchers compared genomes of 20 bird species, including 11 owls that are newly sequenced for the study, and analyzed the nucleotide substitution rates of the individual genes of the birds to identify beneficial mutations kept for generations.
Just as they predicted, they found that the genes involved in sensory perception showed positive selection. This includes acoustic and light perception, photosensitivity, phototransduction, dim-light vision, retina, and inner-ear development.
Furthermore, they also identified 32 genes linked to DNA packaging and chromosome condensation, which looks like these genes inside the owl eyes had evolved and adapted to capture more light similar to the arrangement in retinas found in nocturnal primates. According to computer models, this evolution allows the owl eyes to channel light.
Therefore, the study indicates that owls independently evolved the same DNA packaging mechanism in the retina that enhances the channeling of photoreceptors, which was not yet observed in other bird species until today. The researchers said that their proposed roles of the genes are only suggestions for the moment.
They hope to verify the existence of these light-channeling photoreceptors through direct investigations to validate the findings of their study.
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