For zebrafish, seeing blue, green a matter of life and death

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Color-detecting sensors in human eyes allow us to enjoy vivid and subtle hues in natural and urban environments. But for some creatures, the ability to distinguish colors can be a matter of life and death, according to a study by Japanese researchers.

In a recent study on zebrafish, the team, including University of Tokyo researchers, identified two genes required for blue and green color-detecting sensors.

Fish deprived of these through inactivation were shown to have a competitive disadvantage in feeding frenzies, as they were unable to find their food, the team said.

Generally, the eyes of vertebrate animals have four types of color-sensor cells: purple, blue, green and red. However, mammals are said to have lost blue and green color-detecting cone cells in the course of evolution. It has been known that humans later newly acquired green sensors different from the ones they lost in the past.

However, how blue and green color-detecting cone cells give vertebrates an advantage in survival has remained elusive.

The team identified two genes that control and promote the creation of blue and green color-detecting sensors in the study using zebrafish.

They found that zebrafish with the genes concerned inactivated could not produce blue and green color-detecting sensors.

As a result, the frequency of prey-seeking behavior was lower than that in individuals with untouched genes.

While the zebrafish with inactivated genes can grow to become adult fish, they died after being thrown into a school of zebrafish with non-manipulated genes.

“We want to determine the factors that create blue and green sensors from the same DNA and unravel the evolutionary process of color-detecting sensors,” said Daisuke Kojima, a lecturer on photobiology at the University of Tokyo and a member of the study team.

The study results were published in the Proceedings of the National Academy of Science of the United States of America.

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