The chameleon has been a fascinating creature since its first discovery. For us in the modern generation, the ability of chameleons to change their colour to dazzle mates, scare rivals and confuse and repel predators has been an object of fascination and curiosity. It is only until recently that scientists have uncovered the mechanism behind this amazing feat of chameleons.
In humans and most other animals, pigments such as melanin are responsible for their coloration. But for the chameleons, aside from pigments, materials called guanine nanocrystals in these lizards’ skins are what give them their vibrant colors and the ability to change colors at will, as opposed to the previously held belief of pigments being responsible for their coloration. Scientists from the University of Geneva have uncovered this discovery after years of careful study and research on the chameleon physiology and biological makeup. In their study submitted to the journal Nature Communications, guanine nanocrystals are embedded on a layer of the chameleon’s skin are tuned to alter the reflection of light, giving off different colors depending on the wavelength of light reflected by the nanocrystals.
What sets these amazing reptiles apart from other colour-changing animals is that aside from utilizing the pigment melanin, they also use nanocrystals. If melanin can change the color intensity, the chameleon’s skin nanocrystals allows the reptile to also change the hue of the colors it displays. The color change in chameleons is regulated by transparent guanine nanocrystals (or called photonic nanocrystals) found in a layer of cells called iridophores, which lie just below the chameleon’s pigment cells.
Other reptilians and amphibians such as the poison dart frog also have the same cell layers called iridophores which give them the green and blue colours rarely found in other vertebrates with pigments for color changing.
Colour-switching in chameleons is the domain of males. Although female chameleons also have the same colour-switching capability, it is the males that make the most use of this ability. They use it to make themselves more colorful and attractive to entice mates. Brighter coloration and hue are also utilized by chameleons to ward off challengers and frighten predators. Most of the times, chameleons use their color-switching ability as camouflage for hunting food and for evading predators.
A chameleon’s color can sometimes indicate its mood and temperament. Scientists have discovered that when a chameleon is calm, the nanocrystals in their skin layer become closer to each other and become a dense network of nanocrystals that reflect shorter light wavelengths such as blue. In contrast, when a chameleon is excited, the lattice of nanocrystals in its skin layer loosens and allows the reflection of longer light wavelengths such as yellow, orange and red.
Not only are the crystals used for coloration and camouflage, they are also used to reflect infrared wavelengths from strong sunlight. This also protects the chameleon from sunburn and heat exposure while foraging for food.
The chameleon is truly an amazing animal and a wonder to behold. There are still many more mysteries that need to be unlocked about this fantastic creature, and the team scientists from Geneva have only just begun unlocking one mystery. This revelation of the secret of the chameleon’s color magic doesn’t lessen our fascination with this incredible creature, but instead it only increases our amazement of the magical chameleon.