Also known as Spirobranchus giganteus, the Christmas tree worm is an unusually shaped polychaeta that is a common sight for divers in tropical seas and oceans, close to most coral reef formations. These worms have gotten their names as a result of their Christmas tree-like shape, which develops as a result of its tendency to build highly derived structures for the purpose of easier feeding and breathing. Colorful, sedentary and capable of living in coral reefs for several decades, they are among the most closely studied sea creatures on the reef.
Their brightly colored crowns and repeating disc-like structures are the first elements of the Christmas tree worms’ anatomy you will notice. The worms feature tube-like bodies that only grow to an average of 1.5 inches in length, and their colorful crowns, resembling Christmas trees, are made from small radioles. These hair-like appendages radiate outward from the worm’s central spine, and are mainly used for catching microscopic organisms that are brought by the currents and represent a large part of the worms’ usual diet.
The Christmas tree worm is naturally found in many tropical areas in the Indian and Pacific Ocean. Many species can also be located in the waters of the Caribbean, and the most common place where you will find them is the coral reef. They are easily spotted due to their colorful crowns, and their bodies are usually anchored in the living coral itself. The worms bore a hole in the coral formation and can also secrete a calcareous substance that hardens around their bodies in the shape of a tube. This tube serves as protection against predators and strong ocean currents.
Unlike most reef creatures, Christmas tree worms are extremely sedentary. They tend to choose a single spot inside large coral heads where they will anchor their tube-like bodies and form their homes. Here they will remain, breathing and feeding on microscopic organisms for up to the next 40 years. When predators approach, the worms find it easy to retract into their burrows, and this is the only time when they use up any energy. The Christmas tree worm also prefers shallow waters, usually being found at a depth between 10 and 100 feet, and a particular trait of its biology is that it is capable of both sexual and asexual reproduction.