Serpula

Serpula (also known as calcareous tubeworm, serpulid tubeworm, fanworm, or plume worm) is a genus of sessile, marine annelid tube worms that belongs to the family Serpulidae. Serpulid worms are very similar to tube worms of the closely related sabellid family, except that the former possess a cartilaginous operculum that occludes the entrance to their protective tube after the animal has withdrawn into it. The most distinctive feature of worms of the genus Serpula is their colorful fan-shaped "crown". The crown, used by these animals for respiration and alimentation, is the structure that is most commonly seen by scuba divers and other casual observers.

==Taxonomy== Following is a brief description of the cladistics and taxonomic classification of Serpula: Higher taxonomic ranks The genus Serpula belongs to the family Serpulidae, also known as serpulid worms or tubeworms. Family Serpulidae is one of 31 described families of the order Canalipalpata, also known as bristle-footed annelids or fan-head worms. In addition to the Serpulidae, the Canalipalpata also includes the fanworms (Sabellidae) and a family of deep-sea worms associated with hydrothermal vents (Alvinellidae). Order Canalipalpata belongs to the class Polychaeta, also known as bristle worms. There are more than 10,000 described species of polychaetes; they can be found in nearly every marine environment. Some species live in the coldest ocean temperatures of the abyssal plain, while others can be found in the extremely hot waters adjacent to hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2–3 cm specimen (still unclassified) observed by the robot ocean probe Nereus at the bottom of the Challenger Deep, the deepest spot in the Earth's oceans. Class Polychaeta belongs to the phylum Annelida, also called ringed worms. There are over 17,000 living annelid species, ranging in size from microscopic to the Australian giant Gippsland earthworm, which can grow up to long.