The sea mouse and the photonic crystal

Sea mice (Aphroditidae, Polychaeta) are furry-looking marine worms that for age on, or in, the sea-bed. They are distinguished by an amazing iridescenc e along the lower sides of the body, associated with both hairs and spines known as chaetae. We show by electron microscopic and optical analysis that the iridescence of spines is caused by a highly regular, sub-micron scale structure resembling that being developed for photonic crystals, and that i n fact the sea mouse exploits a partial photonic band gap to achieve its re markable coloration effects.