Science Questions

How does a chameleon change its skin colour so fast and is there any molecular mechanism that's known to underlie that? Gajinder Pal Singh in New Delhi

It's pretty well known how chameleons change their colour. Lots of people think they change colour to match in with their surroundings but it's not actually true. Chameleons change colour to signal to other chameleons what kind of mood they're in. The usual calm chameleon is a pale green colour. So when you see them in Madagascar and Africa which is actually where they're most common, they're that light pale green colour. If you warm them up and put them into a bad mood, they can flash red and yellow and all kinds of funny colours. When they get a bit frisky, they also change colour to attract a mate. But how do they actually do that? It's all down to a very clever system that's not dissimilar to a television screen. In a chameleon's skin, they have these things called chromatophores and these are tiny cells that are laden with pigment. In a normal cell, the pigment is locked away in these tiny vesicles or pouches inside the cell. When a signal comes in from the nervous system or a chemical in the bloodstream, they cell discharges that pigment and it spreads out in the cell and causes the cell to change colour. Depending on which sets of these chromatophores get discharged, then the chameleon changes colour accordingly.

March 2006