Spirobranchus, also known as the Xmas tree worm is a small genus of tube-building annelid fanworms in the family Serpulidae. Spirobranchus giganteus, is a Christmas tree-shaped serpulid tube-dwelling worm with magnificent twin spirals of plumes used for feeding and respiration. This cone-shaped worm is one of the most widely recognized sedentary polychaete worms. They come in many colors including orange, yellow, blue, and white and, though they are small with an average 3.8 cm in span, the are easily spotted due to their shape, beauty, and color. The colorful plumes, or tentacles, are used for passive feeding on suspended food particles and plankton in the water. The plumes are also used for respiration. Though the plumes are visible, most of the worm is anchored in its burrow that it bores into a live calcareous coral. Christmas tree worms are very sensitive to disturbances and will rapidly retract into the burrow at the slightest touch or passing shadow. They typically re-emerge a minute later, very slowly, to test the water before fully extending their plumes. Spirobranchus giganteus, is found on coral reefs in tropical waters worldwide. The Christmas tree worm, Spirobranchus giganteus, are polychaete ciliary feeders that feed using their radioles, the hair-like appendages that circle outward from the central spine, to catch phytoplankton floating in the water column.
