Shapeshifters of nature: Sometimes the answer is just beneath the skin

Animals and insects have pigments that help camouflage or send out warning signals but the only species that seems to have trouble with pigments and pigmentation are humans.

Be it the flaming oranges, golds and reds of autumn leaves, the myriad shades of green in new leaves as they unfurl or the dark fur of a bear or the crimson blood flowing through our veins, all colour in nature is caused by a handful of pigments. These are solid specialised chemical compounds usually beneath the surface that absorb and reflect various wavelengths of light, alone or in conjunction with each other.

Some, like the carotenoids - responsible for red and yellow - are acquired through diet, (which is why flamingos in many zoos are fed a carotenoid rich diet to enhance their pinks and scarlets). Others, like melanin - dealing in dark browns, and blacks are inherent as are pterins. There are just a handful of them - carotenoids, melanin, pterins which create vivid red, yellow and white pigments commonly found in insects, fish and amphibians. Then there's chlorophyll responsible for the green in plants and trapping energy from the sun. There's also luciferin, which give fireflies and deep-sea creatures their lights.

Pigment colours (unlike structural colours) remain the same no matter what the viewing angle. Plant pigments may enhance certain colours, like to make them more attractive to pollinators. In autumn, the prominent pigment chlorophyll degrades into colourless tetrapyrroles (also known as non-fluorescent chlorophyll catabolites), bringing forth the hidden pigments of yellow (xanthophylls) and red (carotene).

Animal pigments may be used for camouflage, mimicry or as a warning (such as in the arrow-poison frogs). Some reptiles, such as chameleons are armed with colour changing pigments called chromatophores, which contain vesicles which are like little pots of three different coloured liquid 'paints' and are closely attached to muscles, nerves and sheath cells.

There are three kinds of specialised chromatophore cells, the erythophores - responsible for the reddish pigments, melanophores, containing melanins responsible for blacks and browns and xanthophores, responsible for yellow and reds containing carotenoid pigments. Together, they mix and match producing a palette of colours, depending on the state of mind of the animal - whether it wants to camouflage itself from potential predators, show off to a potential mate or warn off a rival.

These lie just beneath the surface of the skin, or fur and again, while some, the biochromes, are designed to take in certain light wavelengths and reflect the others, the schematochromes are quick change artistes, that use structural colours and change colours depending on the angle of viewing and light.

The shimmering gorgeous colours of a hummingbird's throat and gorget, the plumage of peacocks and starlings, the iridescence of a jewel beetle, whose colours change depending on the angle of viewing, and of so many other birds and fish are due to what are called structural colours. Unlike the 'standard issue' pigments like carotenoids and melanins, which absorb and reflect certain wavelengths of light, these pigment cells act as tiny prisms or mirrors, reflecting and refracting light waves, the colours may morph or disappear completely depending on the angle of viewing. I remember a jewel beetle I picked up a long ago in Kasuali, it was shiny rainbow hued, but when I picked it up and photographed it, turned completely drab, completely losing its lustre.

The microscopic layers of 'mirrors' may contain alternating layers of keratin and melanosomes. Light bounces off both the top and bottom of these microscopic layers at different depths and when they overlap, either amplify the colours (constructive interference) or cancel them out (destructive interference) revealing only the dark melanins below.

The purpose of this shape shifting, could be camouflage from predators, or to attract a mate - as in the birds of paradise. A jewel beetle that may seem leaf green from the top, and invisible to a potential predator, but may look gorgeous when glad-eyed from the side by a potential mate, but there is no telling how the beetle has this knowledge! Often the flashing of gorgeous colours is accompanied by a ritualised dance, to keep the attention on the would-be lover!

Then there are those, who change colour depending on the season. Arctic foxes and hares, pure white in winter, when the snow comes down, turn orange and brown in summer via a splotchy in-between phase where again they meld into their semi-melted environment - evolution playing yet another genius card to keep them out of harm's way!

The only species that seems to have trouble with pigments and pigmentation is ourselves. People living in the hot, equatorial zones of the world are usually dark, due the high amount of melanin they have to ward off dangerous UV light. Those in the colder temperate regions are pale and fair and consider their ebony hued compatriots as inferior. This problem has persisted even after the notorious slave trade was ended - the blacks vs whites, conflicts rage on. Those in the tropical rainforests of Central and South America are a beautiful golden brown, and the envy of the world. We Indians, usually a pleasant nut brown, yearn to be 'fair and lovely' and with us the demarcation between dark and fair is stark. Those living in the south are dark, those in the north fair, which by no means makes them better or cleverer or superior in any way! People living in Central Asia, in China and Mongolia are 'yellow' and also treated with disdain by the 'whites'.

Animals, which have much lower IQs than ourselves, have no such prejudices. A polar bear will not think a grizzly bear is 'inferior' because of its colour, even if it is 'superior' because it is larger and stronger. And anyway, under that pristine 'white' fur, the polar bear is actually black.