Chameleons are famous for their ability to change color. Earlier the secret behind this uncanny ability of these old world lizards was not known. However, a recent study has revealed that these reptiles do so by rapidly adjusting a layer of special skin cells.
Chameleons are surely not the only animal species to change color; other animals like octopus and squids also have similar abilities. However, what separates chameleon from those aquatic species is the fact that unlike octopus and squids, chameleons don’t change their skin color by dispersing or accumulating skin pigments.
During the above-mentioned study, researchers discovered that the lizards modify their body color through structural changes. These structural changes alter the way light reflects off the skin of these reptiles, which eventually modify their skin color.
In order to find out the secret behind the color-changing ability of these lizards, scientists studied a total of 13 chameleons. Out of them four were adult females, five were adult males and the remaining four were juvenile panther chameleons. For those who don’t know what panther chameleons are: they are a lizard species native to Madagascar; their scientific name is Furcifer pardalis.
During this elaborate study, researchers came to know that chameleons possess a couple of superposed thick skin layers containing iridophore cells or pigmented iridescent cells that reflect light.
Iridophore cells consist of nanocrystals of various shapes, sizes and organizations, which hold the key to the color-changing ability of these reptiles. Researchers found that a chameleon can alter the structural organization of the upper iridophore cell layer by exciting or relaxing its skin; and this alteration results in the change in its skin color.
According to Michel Milinkovitch, a senior author of the study, when a chameleon’s skin is relaxed, nanocrystals within its iridophore cells remain extremely close to each other. At this stage, cells primarily reflect short wavelengths, for instance, blue.
When the skin is in an excited state, the distance between two neighboring nanocrystals starts increasing. This allows every iridophore cell to selectively reflect longer wavelengths, for instance, red, orange or yellow.
The researchers adopted a number of procedures for testing the iridophore cells and finding out the exact factors causing color changes in these lizards. They used advanced videography for filming the color changes in chameleons and also built numerical models that could predict how nanocrystals must reflect light.