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Wrasse eye

(Photograph) - Gaze into the emerald eye of the corkwing wrasse and you see a bold, abstract masterpiece of reds, blues and greens. Yet for whom was this tiny work of art created and why?

This vivid, little fish was startled by being photographed during a night-time dive in Vigo Bay, north-western Spain. It was merely displaying a shock of colour that characterises its kind - nothing special to any other corkwing wrasse.

But then the artist wielding nature's paintbrush on the wrasse, as well as a myriad of other creatures, is the most remarkable exponent of creativity - evolution. Its palette is almost unlimited, its imagination unrivalled. For fish such as the wrasse, colours are usually carried in specialist cells that contain tiny particles of a particular pigment.

For instance, those cells containing melanin - the substance that darkens human skin - appear black or brown, while others hold carotenoids, the same chemicals that make carrots orange.

The colours are then shaped into intricate patterns during the fish's development, following instructions laid down in the animal's genes.

Why? There is not one, but many influences at work. For some fish, it is a matter of camouflage to evade predators.

Quite often it may simply be a case of trying to attract the opposite sex. It may even be a way to show an emotional state - whether excited or afraid.

Nature's artistic zeal is, of course, not confined to the water. In the air, many a butterfly has also been blessed with a splash of colour. Scientists have studied the motives of the artist here more thoroughly than for fish.

Some butterflies attempt to hide from predators by mimicking the colour of a dried-out leaf. Conversely, othersbear loud hues to warn that the insect is poisonous and should be left alone. A few mimic the latter in a cunning attempt to deceive. Some demonstrate virility to intimidate rivals, while others are attempting to attract sexual partners.

A few even dare to push the palette past its conventional range and into the ultra-violet "colours" of a wavelength that the human eye cannot perceive. So some butterflies that appear plain may be wildly patterned to the right observer.

The appearance of a particular species is thought to depend on the interplay of all these factors. Over millions of years, mutations of DNA in pigmented cells produce variations. Survival of the fittest is the rule, so those whose pattern gives them an edge will have the best chance of reproduction.

The habitat the insect - and presumably the fish - enjoys will ultimately determine whether it gets to be illuminated like a Van Gogh canvas or winds up as gloomy as a Mark Rothko.

Web links Wrasses: http:saltaquarium.about.competssaltaquariumblwrassefam.htmButterflies: Wildlife photographer of the year: Reader offer This picture was highly commended in the BG Wildlife Photographer of the Year 2000 competition. TES readers can buy the book, Wildlife Photographer of the Year - Portfolio Ten, at the special price of pound;22.99, including pamp;p. Call 01795 414952 with credit card details (lines open 9am-5pm, Mon-Fri). The photographs are also being exhibited at the National History Museum in London from October 28 to February 25.

STEVE FARRAR. Photograph by Jose Luis Gonzalez.

Steve Farrar is science reporter for The Times Higher Education Supplement

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