Chameleons change colour by tuning nanoscopic structures in their skin cells to reflect different wavelengths of light.

Credit: J. Teyssier, S. V. Saenko, D. van der Marel and M. C. Milinkovitch

Michel Milinkovitch and his colleagues at the University of Geneva, Switzerland, studied skin cells of the panther chameleon (Furcifer pardalis) from Madagascar. They found that the lizards have two layers of specialized cells called iridophores. Each layer contains light-reflecting guanine nanocrystals. By altering the spacing between the crystals in the upper layer, the cells shift from reflecting blue light to reflecting yellow or red wavelengths, which interact with the chameleon's yellow pigments. This produces a change in colour from green (pictured, left) to yellow–orange (right). The deeper layer consists of cells that reflect a broad set of wavelengths, particularly those in the near-infrared range.

The first layer of cells allows the animals to quickly switch between camouflage and an ostentatious display to attract mates or expel a rival male, whereas the second layer provides thermal protection.

Nature Commun. 6, 6368 (2015)