Octopuses can quickly change the color of their skin to blend in with their environments, making them masters of camouflage. However, octopuses only have a single type of light receptor in their eyes, meaning they technically are colorblind. So, how can these experts of color camouflage distinguish different colors? The secret lies in the shape of their pupils, which are rectangular.
Unlike human eyes, the octopus’s wide and unusual pupils take in light from all directions. This allows white light to be separated into its component colors in different wavelengths. If you’ve ever had your pupils dilated, you may have experienced this effect, called chromatic aberration—looking at a light with wide, dilated pupils produces rings of color around the light source.
After the colors are separated, experts have proposed that octopuses focus different color wavelengths on the retina using a variety of physical actions—including changing the distance between the lens and the retina. This allows the octopus to distinguish different colors, even though they may not be “seeing” colors like humans and other animals do.
Learn more about otherworldly octopuses!