Mantis shrimp, the psychedelic reef-dwellers that can wallop their prey with an astounding 200 pounds of force, have a large collection of unique qualities. One is an unusually large number of photoreceptors, the light-sensing proteins that contribute to color vision. Humans have three types of color receptors, birds and reptiles have four, and mantis shrimp have an astounding 12 different kinds.
Each type of photoreceptor samples a small set of wavelengths in the color spectrum, but our vision demonstrates that just three or four channels are sufficient to distinguish between different hues even on a very fine scale. Why, then, would these creatures need 12 types of photoreceptors?
According to a new study in Science, mantis shrimp may use a vision system previously unknown to science. This key to this realization was the finding that despite having so many different photoreceptors, the animals have trouble distinguishing between similar colors.
If you’re wondering how to determine whether an animal can discriminate between, say, burnt orange and dark yellow, you probably aren’t alone. But it’s surprisingly simple to test animals’ color vision: just teach a bee, dog, or mantis shrimp that a specific color delivers a food reward, then offer that animal an array of colors to choose from. If the animal is capable of distinguishing between certain colors, it will approach the rewarding hue more often than would be expected by random chance.
The authors of the study used this time-tested method to determine the limits of mantis shrimps’ color discrimination abilities. The shrimp were able to accurately distinguish between different colors of light when the wavelengths were between 50 and 100 nanometers apart. But when the colors were more similar—the wavelengths differed by just 12 to 25 nanometers—the shrimp’s accuracy dropped to about 50 percent, or what would be expected if they were choosing randomly.
Loading comments...
