How do Chameleons change colour?

Credit: Pixabay

A ballistic tongue as long as its body, independently moving eyes capable of 360° vision and claws perfectly adapted to surviving in an arboreal habitat; these are the features that constitute the spectacle that is the chameleon. But the most astonishing feature is surely the capability to instantly transform its appearance. Whether in response to its environment or for use in communication, the chameleon’s ability to change colour is a skill boasted by only a few other species in the animal kingdom.

Located in the dermis and epidermis is the cell responsible for the chameleon’s famed super-power: the chromatophore. Chromatophores are specialised cells that contain pigments in their cytoplasm. These pigments produce colours by reflecting and absorbing wavelengths of light. A chameleon has three types of chromatophores, which are arranged in layers and which each produce different colours. Melanophores lie deepest in the skin and contain black pigments, iridophores found above create blue colours and the top most chromatophores are xanthophores, which make red and yellow colours.

The chameleon changes its colour by altering the concentration and movement of the pigments; the intensity of colour depends on the amount of aggregation/dispersal of the pigments. These colour changes are rapid as the chromatophores are under direct neural control. This quick reaction time is important in social situations where chameleons use their colours to communicate with one another. Animal communication is vaguely defined as a transfer of information that causes a change to the receiver’s present or future actions. So it’s easy to see why precise and correct signalling is imperative, especially when information regarding mating or territory is being exchanged.

The importance of chameleon’s colouration in social signalling was demonstrated by a study published in 2008. The paper published in PLoS Biology reported that colour changes in chameleons evolved as a result of social signalling rather than as a method of crypsis against predators. The study found that evolutionary shifts for colour change in the southern African dwarf chameleon (Bradypodion spp.) were associated with increasingly conspicuous signals used in male contests and courtship. Like other species that develop conspecific signals, the chameleon uses coloration as an effective method to communicate with its intended audience, whilst not revealing itself to predators.
It’s not only chameleons that can change colour; other vertebrates, like fish and invertebrates like squid and numerous crustaceans also have the ability. In each organism the technique has been perfected and enhanced in order to increase the chances of survival.

References:

Anderson  (2004). Historic and Contemporary Theories on Chameleon Color Change. Chameleons! Online E-Zine, http://www.chameleonnews.com/04NovAndersonColor.html

Fox & Moussalli (2008) Selection for Social Signalling Drives the Evolution of Chameleon Colour Change. PLoS Biol
http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0060025

Nilsson (1983) Autonomic Nerve Function in the Vertebrates Zoophysiology
http://link.springer.com/book/10.1007%2F978-3-642-81974-2

Schubert (2013) Chroma + Phy – A Living Wearable Connecting Humans and Their Environment. Biomimetic and Biohybrid Systemshttp://link.springer.com/chapter/10.1007/978-3-642-39802-5_61