Chameleons boast some of the brightest colors seen in nature. They can also go from a subdued green to bright red in a matter of minutes. So how do they do it?
When white light enters a glass prism, the light is refracted, and each of its color components is slowed by a different amount and thus bent at a slightly different angle. The other surfaces of the prism can then be used to direct the different colors of light either on paths forward or to be reflected back.
The behavior of light as it travels through a prism was one of the key discoveries that contributed to our understanding that light can act like a wave and like a particle, a phenomenon known as the wave-particle duality in quantum mechanics.
Chameleons as prisms
So now you may be wondering what all this prism talk has to do with chameleons since they are most definitely not made of glass. Research has recently shown that chameleons are able to produce some of their color changes using a technique similar to that of a prism and not entirely based on pigments in their skin as was previously thought.
The study conducted by a combination of quantum physicists and evolutionary biologists at the University of Geneva was based on panther chameleons which are typically an olive green in order to blend in with their surroundings. They can change to a stunning red and yellow in a matter of minutes, however, when they are trying to show off, either for a prospective mate or an enemy.
When the biologists looked at the chameleon’s skin under the microscope, they found that while there were pigments capable of producing some of the warmer tones like the dark greens, there were none to explain the bright reds and yellows seen in those reptiles.
Instead they found two layers of cells called iridophores made up of hundreds of thousands of guanine crystals: the first layer showed the crystals in a very ordered, grid-like arrangement while crystals were placed much more at random in the lower layer.
The physicists were able to show in a computer simulation that changing the distance between the crystals would effectively act like a prism to reflect different colors of light. When the crystals were close together, they reflected short wavelengths, or blue, light, while the rest of the colors passed through. When the crystals moved farther apart, the longer wavelength or red light was reflected instead.