Chameleons

[Johnny Pebs]

Does anyone know how they go about changing colors? And if a chameleon can change colors, how come a leopard can't change its spots?

[Kat]

According to this article (http://encarta.msn.com/find/Concise.asp?ti=00AB9000) in Encarta:
The chameleon changes color when it is frightened and in response to light, temperature, and other environmental changes. The color change is caused by hormones that affect special pigment-bearing cells in the skin. Its color does not always change to match its surroundings, however, as is commonly believed.

And What makes a chameleon change color (http://medinfo.wustl.edu/~ysp/MSN/posts/archives/mar97/857252824.Zo.r.html) by Tim Susman, Staff Zoology, University of Minnesota, St. Paul, MN says:
Chameleons change color for a variety of reasons. Cells called chromatophores in their skin redistribute pigment to cause the color change. The chromatophores are triggered by hormones, which can be sent out in a variety of circumstances.

I would guess that other animals (including leopards) cannot change color(s) because they have neither the cells that redistribute pigment nor the hormones that trigger those cells.

[Wood Thrush]

Many lizards — and even other animals, like cuttlefish — can change color. They usually do use chromatophores.

Chromatophores do not, in and of themselves, cause color change; many fish contain chromatophores and yet cannot change color. In animals like cuttlefish, the chromatophores contract or expand. IIRC, this is via the contraction or relaxation of a muscular ring surrounding the chromatophores. It's the same as how your iris contracts to enlargen the pupil, execpt the "pupil" (chromatophores) are colored and the "iris" is not. The chromatophores come in different colors and the relative combination of the base colors causes them to mix, like an RGB monitor.

Also, birds and mammals cannot change color over their entire body like a chameleon because their epidermis, or uppermost skin layer, is not visible.

By the way, birds and mammals can change color, but this is usually by altering bloodflow — humans and caracaras blushing are classic examples.

[Johnny Pebs]

I would guess that other animals (including leopards) cannot change color(s) because they have neither the cells that redistribute pigment nor the hormones that trigger those cells.


Thank you Kat and Thrush for the info, but actually I wasn't serious about the leopard thing. It was my small(read "lame") attempt at humor.:)