Cephalopods May Use Chromatic Aberration to Detect Colors

Cephalopoda is a class of animals that includes octopuses, squids, and cuttlefish. They are capable of dramatically changing their colors and patterns. This ability allows them to use camouflage, confuse predators, and communicate with each other. They’re able to blend in with their environment perfectly, an amazing feat for animals with a single photoreceptor. A new study published in the journal Proceedings of the National Academy of Science provides a possible explanation for how an animal with monochromatic vision manages to mimic colors in their environment.

Cuttlefish and other cephalopods are able to perfectly copy the colors and patterns in their natural environment. Scientists have long wondered how this is possible when they can only see in black and white. They clearly have some way to detect colors even with their lack of visual pigments. This new study proposes a potential mechanism based on the concept of chromatic aberration.

If you’ve ever used a camera with a lower quality lens, you may have experienced chromatic aberration. Chromatic aberration is an effect that occurs when a lens fails to focus different wavelengths of light at the same convergence point. The light wavelengths focus at different distances, resulting in a fringe of color along the sections where the dark and light parts of an image meet. Using computer models, the researchers were able to show that this effect can be manipulated in order to determine information about which colors are in the environment. If cephalopods are capable of taking advantage of this effect, they could gain information about the colors and patterns around them without technically “seeing” the colors.

Interestingly, cephalopods have U-shaped non-axial pupils. The researchers found that such pupils are ideal for exploiting chromatic aberration, providing further evidence that this may be how they detect colors in their environment. The authors note that other animals, including spiders and dolphins, may take advantage of the same mechanisms.

This recent study provides new insight and explanations for how cephalopods manage to use detailed camouflage without the ability to see colors. The researchers hope that their findings will lead to further studies on cephalopod vision.

REFERENCE

Stubbs, Alexander L., and Christopher W. Stubbs. Spectral discrimination in color blind animals via chromatic aberration and pupil shape. Proceedings of the National Academy of Science (2016).

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