Christmas tree worms, (Spirobranchus) are Christmas tree-shaped serpulid tube-dwelling worms with magnificent spirals of plumes used for feeding and respiration. These cone-shaped worms are 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, they 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. coral. plumes.