The research team of Laboratory of Artificial & Natural Evolution, University of Geneva, led by Michel Milinkovitch, published this year in the Nature Communications Journal their latest findings on the dynamic color change of chameleons.
The results of the research, based on the study of Panther Chameleon (Furcifer pardalis), indicate that although chameleons of both sexes and all ages can strongly modulate the brightness of the skin, for example in response to stress, adult males are additionally characterized both by exceptionally large intraspecific colour variation (with various combinations of white, red, green and blue skin) and their ability to rapidly change colour (hue). Indeed, when encountering a male competitor or a potentially receptive female, a mature male panther chameleon can shift the background colour of its skin from green to yellow or orange, whereas blue patches turn whitish and red becomes brighter with less conspicuous hue modifications. This process occurs within a couple of minutes and is fully reversible.
According to the researchers, complex and rapid variations of chameleons color are due chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of their skin. In other words, one could say that chameleons have “a crystal dress”. When the chameleon is in relaxation guanine nanocrystals form a dense mesh and reflected light blue. By contrast, when the male chameleon wants to attract a female or challenge a competitor stretches the skin and guanine nanocrystals are separated and reflected light red or yellow.
Teyssier J., Saenko S.V., van der Marel D. & Milinkovitch, M.C. (2015). Photonic crystals cause active colour change in chameleons. Nature Communications 6:6368. doi: 10.1038/ncomms7368.