Swiss researchers have discovered how chameleons accomplish their vivid colour changes: they rearrange the crystals inside specialised skin cells.
It was previously suggested that the reptiles’ famous ability came from gathering or dispersing coloured pigments inside different cells.
But the new results put it down to a “selective mirror” made of crystals.
They also reveal a second layer of the cells that reflect near-infrared light and might help the animals keep cool.
Reptiles make colours in two ways: they have cells full of pigment for warm or dark colours, but brighter blues and whites come from light bouncing off physical elements like these crystals: so-called “structural colours”.
These colours can also be mixed. A vibrant green might arise from a structural blue overlaid by yellow pigment.
A panther chameleon can switch in minutes from camouflage colours to more strident, communicative ones
Some changes arise from shifting pigments. Tiny packets of the dark dye melanin, for example, can be spread throughout the tendrils of big “melanophore” cells – or gathered into the centre, to lighten the skin again. Many fish and reptiles grow lighter or darker in this way in response to stress, or to match their surroundings.
More on: www.bbc.com/news/science-environment-31819588
