A paper posted in the Nature Communications Journal aims to demonstrate how chameleons can change their skin color for multiple purposes by manipulating crystal cells situated under their skin.
The study was done by a University of Geneva team comprised of researchers Suzanne Saenko, Michael C. Milinkovitch, Jeremie Tessyer and Dirk van der Marel and is entitled suggestively “Photonic crystals cause active colour change in chameleons” .
By observing a range of both male and female, adult and juvenile panther chameleons – a type of chameleon native to Madagascar –, the researchers found out that the lizards have two pigmented layers of crystal cells – named iridophore cells – which can be used to reflect light in different ways.
These iridophore cells are comprised of nanocrystals whose arrangement can change depending on the lizard’s state, which also changes the way it reflects light and ultimately modifies its skin color.
“When the skin is in the relaxed state, the nanocrystals in the iridophore cells are very close to each other — hence, the cells specifically reflect short wavelengths, such as blue,” explained Milinkovitch, professor of genetics and evolution within the University of Geneva.
Milinkovitch also said that excitement of the chameleon’s skin – caused by the apparition of a male rival or a female – will further the gap between its nanocrystals and cause longer wavelength colors such as red, yellow or orange to be reflected.
Their famous green camouflage is actually a combination of the blue reflected when the crystals are close one to another with a high amount of yellow pigment that the elusive lizards happen to hold under their skin.
The second layer of nanocrystals in the chameleon’s skin is responsible for reflecting a big part of the infrared wavelengths and thus provides the lizard a highly effective shield against continuous exposure to the sun.
This sets the chameleon apart from other animals that change colors based on the build-up and dispersal of pigments within their skin, such as squids. The nanocrystal manipulation demonstrated by the research seems to be an evolutionary trait that until now seems specific to chameleons.
The research also showed that only adult male chameleons are the only ones capable of changing colors, due to the fact that females and juveniles have way fewer iridophore cells in their upper layer.
Image Source: Phys