Natures wonders: Camelion color change (Introduction)

by David Turell @, Monday, September 21, 2015, 18:52 (1546 days ago) @ David Turell

They use skin prisms to break light into various colors:

"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.

"These gridded crystals in the chameleons' skin cells thus appear to act as a “selective mirror” to reflect only certain wavelengths of light, thus changing the chameleon's color. These different crystal arrangements could, in theory, also work with the chameleon's pigments to create even more colors, for example, combining a pigmented yellow with a reflected blue to make a bright green.The biologists took this theory beyond the computer simulation by changing the distance between the crystals in skin cells in the lab. Cells dipped in salt water of varying concentrations swelled to varying degrees thus changing the spacing between the crystals. Their lab results reflected the predictions of the simulations.Further bolstering the connection between the crystal spacing and the skin color changes is the fact that the female and young panther chameleons, which are not able to change color, do not have the special iridophore cells.Now what about that second lower layer of cells with bigger, more disorganized crystals? The scientists believe this layer may act to reflect near-infrared light. While reflecting optical light can produce different observed colors, reflecting near-infrared light can act as a cooling mechanism by deflecting the sun's rays."

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