© Peter Parks, AFP/Getty ImagesResearchers at the Washington University School of Medicine in St. Louis have discovered light receptors in a chicken's eye allow the bird to see more colours than humans.
Researchers at the Washington University School of Medicine in St. Louis have discovered light receptors in a chicken's eye allow the bird to see more colours than humans. The findings, published February in the scientific journal PLoS One, found receptor cells in a chicken's retina are laid out in mosaic-like patterns, organized in a way that gives chickens, and other birds, more sensitive vision than most other mammals.
"I think birds really do see colour in a way different from humans," said Joseph Corbo, senior author of the study and assistant professor of pathology, immunology and genetics.
"That's hard for us to imagine. We don't really know what's in the mind of a chicken," he said.
Vision comes from light-sensitive receptor cells in the retina - a light-sensitive structure at the back of the eye.
The human retina can detect red, blue and green wavelengths, said Corbo.
But a bird retina can also detect violet and even some ultraviolet wavelengths, he said. As a result, birds may have "an entirely additional dimension" to their colour vision, Corbo said.
He described it as, when humans see three green dots, a chicken may see three different coloured dots depending on the varying degrees of violet or ultraviolet light in it.
The researchers also found chickens have a special receptor that helps them detect motion.
"Based on this analysis, birds have clearly one-upped us in several ways in terms of colour vision," said Corbo in a statement.
Corbo said their findings could eventually help scientists find news ways, such as stem cell therapy, to treat the nearly 200 genetic disorders that can cause blindness.
"In many human diseases that affect the retina and cause blindness, you get a loss of photoreceptors," said Corbo.
For a blind person who has lost photoreceptors, scientists could eventually be able to differentiate stem cells into photoreceptors to be used for replacement therapy.
"Understanding how this process occurs in birds could help in stem cell differentiation for humans," said Corbo.
In addition to chickens, the researchers also studied three other bird species: woodpecker, pigeon, and sparrow. They found the photoreceptors in those birds "fundamentally similar" to that of a chicken.
"So we believe that this is quite a general phenomenon amongst birds," said Corbo.
Being able to see more colours is an evolutionary trait that gives birds an advantage over other animals, said Corbo.
As many bird species are brightly coloured, Corbo said sensitive colour vision helps them in mating, and in feeding, especially on brightly coloured fruit.
Source: Canwest News Service
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