An image of Favites pentagona coral in Long wave UV Light showing green and orange Fluorescence. This species of coral will glow brightly when illuminated in ultra-violet(UV) light. Each head of coral is formed by a colony of genetically identical polyps which secrete a hard skeleton of calcium carbonate; this makes them important coral reef builders. It is thought the glow may attract symbiotic algae, or protect the coral from the intense ultraviolet light of the Sun in shallow water. This image is part of a series showing the identical specimen in white light and UV light.