"Back in the museum I finally discovered its story." Kjell tells us. "The quarter-sized red spotted guard crab lives on the 'Pocillopora' coral, where it finds safety among the coral's branches and feeds on its secreted mucus. In return the crab protects the coral from its predators, usually sea stars. The crab may pick up, shake and throw off small sea stars... a lesson not soon forgotten. Larger sea stars such as the Crown of Thorns it pinches and jerks until they leaves to seek another less protected coral." Even in the absence of sea stars, the coral is healthier overall with its guard crab.