Christmas tree worm (Spirobranchus giganteus) on Hump coral

   Adult Spirobranchus giganteus are obligate mutualists of living madrepore corals. By settling on the surface of the colony, the worm gains better protection from predators. In turn, its large tentacles are capable of scaring away the coral-eating crown-of-thorns starfish from nearby parts of the coral colony. In addition, due to the beating of the cilia that cover the tentacles of Spirobranchus giganteus, the speed of water flow over the surface of the corals, which also feed on plankton, increases.