Chameleons

Change of color
http://www.answers.com/topic/chameleon

All chameleon species are able to change their skin colour. Chameleons change their colour in response to light exposure and ambient temperature.

Different chameleon species are able to change different colours which can include pink, blue, red, orange, green, black, brown and yellow. Chameleons are naturally coloured for their surroundings as a camouflage. However, recent research has indicated that Chameleons may use colour changes as a method of communication, including to make themselves more attractive to potential mates.

Chameleons have specialized cells, collectively called chromatophores, that lie in layers under their transparent outer skin. The cells in the upper layer, called xanthophores and erythrophores, contain yellow and red pigments respectively. Below these is another layer of cells called iridophores or guanophores, and they contain the colourless crystalline substance guanine. These reflect, among others, the blue part of incident light. If the upper layer of chromatophores appears mainly yellow, the reflected light becomes green (blue plus yellow). A layer of dark melanin containing melanophores is situated even deeper under the reflective iridophores. The melanophores influence the 'lightness' of the reflected light. All these pigment cells can rapidly relocate their pigments, thereby influencing the colour of the chameleon

A skin of many colors
http://www.sandiegozoo.org/animalbytes/t-chameleon.html

How chameleons change color is a fascinating and complicated process. First of all, they don't really change color to match their surroundings, and they cannot change to any and all colors. For example, if a chameleon is sitting on a red-and-white polka dot tablecloth, it will not turn red and develop round white spots!

Chameleons don't look at what they're sitting on and deliberately decide to match it. Instead, each species of chameleon has a group of patterns and colors that it is able to display; some of these patterns are designed for camouflage. The skin color changes under the influence of the lizard's mood, such as fear or anger, the amount of light, and the temperature or humidity. The changing skin color also plays an important role in communication among males.

So how do they do it? Chameleons have four layers of skin: the outer, protective layer called the epidermis; the chromatophore layer that contains yellow and red pigments; the melanophore layer that contains the dark pigment melanin and can create brown and black colors or reflect blue; and the nether layer, which only reflects white. Nerve impulses and hormone changes cause the color cells in these layers to expand and shrink, and the blending of the different layers creates the colors and patterns that we see.

An email received December 2008