고등학교 영어Ⅱ (미래엔 김성연) 연계 글

Human color vision relies on just three types of receptors, commonly described as red, green, and blue channels. The brain identifies colors by comparing how strongly each channel responds, and birds, monkeys, frogs, and fish do the same. With only three or four channels, this method lets an animal tell apart shades that differ only slightly.

Mantis shrimp, a group of crustaceans, possess one of the most complex eyes in the animal kingdom. Some species have twelve types of receptors, which together detect light from deep ultraviolet to far red. This richness has long puzzled scientists: why would an animal need twelve channels when three or four are enough? If our eyes had twelve kinds of receptors instead of three, we might expect to notice countless shades that now escape us. In theory, mantis shrimp should be far better than humans at telling similar colors apart.

To test this idea, Hanne Thoen of the University of Queensland and three colleagues studied one reef species, Haptosquilla trispinosa. They trained the shrimp to choose a particular color by rewarding each correct choice with food, and the animals learned quickly. Early pairs, such as red and blue, differed greatly, but later pairs sat closer and closer together along the spectrum until the shrimp began to make mistakes.

The shrimp's performance, which the team reported in the journal Science in 2014, was surprisingly poor. The shrimp were not as good as humans at telling similar colors apart, and they also did worse than bees and fish. If the shrimp compared signals in the way that we do, twelve channels would make them experts at this task. These poor scores therefore ruled out the familiar system of comparison and pointed to a completely different one. The team proposed that the shrimp scan objects by moving their eyes and identify colors from signals that arrive over time. This method is suited to recognizing colors rather than to telling close shades apart. It is not as precise as ours, but it lets the nervous system stay simple instead of interpreting every piece of information that the eyes collect.

Justin Marshall, who supervised Thoen's doctoral research, called the finding totally unexpected. He pointed out that no other way of processing color had been identified since scientists first described color vision in the 1800s. More receptors, it turned out, were not as helpful for fine distinctions as many people had assumed. If curiosity never led scientists to question ideas that seem obvious, surprising answers like this one would remain hidden.