Recent research shows that although sea urchins have no eyes, they see very well. How?
Answer:
The entire body of the sea urchin is light sensitive, but its spines are not. Instead, the spines break up the light pattern into small areas, much as a computer image is made up of pixels. The more spines an urchin has, the higher the resolution of its sight. Many can see well enough to recognize predators and food.
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