Serpulidae Family of Christmas Tree Worms

One Christmas Tree Worm of the Serpulidae Family is found in this website:

Giant Christmas Tree Worm, Spirobranchus giganteus. A representative of the Serpulidae Family of Christmas Tree Worms.

Phylogeny: Christmas Tree Worms of the Serpulidae Family, along with earthworms, belong to the phylum Annelida. Their bodies are composed of ringed segments. Their body cavities are filled with coelemic fluid which, hydrostatically, provides rigidity to the body. Annelids have well-developed circulatory, digestive, and nervous systems. Serpulids are in the class Polychaeta, which stems from the Greek words meaning “many bristles”. The bristles are chaete, chitinous setae, or spines, that assist the animal with movement, swimming, or anchoring. Most polychaete are free-living, but some live in tubes, burrows, or as parasites inside other animals. Christmas Tree Worms are in the subclass Sedentaria, the infraclass Canalipalpata, and the order Sabella.  Sabellids are tube-dwelling, constructing their tubes either from cemented grains of sediment or from calcium carbonate. The Serpulidae Family is one of four families in this order. The Serpulidae Family contains three subfamilies, eight tribes, seventy-three genera, and around five hundred sixty-eight  species, though some sources go as low as three hundred species and some as high as six hundred species. The name Serpulidae comes from the Greek word meaning “little serpent” or “little snake”. This refers to the curving appearance of their tubes.

Morphology: Serpulid Christmas Tree Worms inhabit calcareous tubes that are composed of a mix of calcium carbonate and mucopolysaccharides. The tube may be straight or curved, but not spiraled, except at its very beginning. They are characterized by a cone-shaped structure made up of feather-like radioles (branches) at their anterior end that attach to a lobe surrounding the mouth. This structure is known as a branchial crown and used for respiration and food gathering. The setae of the radioles may be smooth or hooked. One radiole in the structure is modified to serve as an operculum (trapdoor) that closes when the animal withdraws into its tube. Serpulids are very quick to retract into their tube when they sense changes in water movement or light that they associate with a predator. Christmas Tree Worms have distinct thoracic and abdominal segments and eye spots that vary widely in complexity. The majority are brightly colored. Large Serpulids reach a maximum of 20 cm (7.9 inches) in length. Abandoned Serpulid tubes may break loose and closely resemble sea shells of the Vermetidae Family of Worm Shells . The two can be distinguished by Serpulid tubes having a dull interior finish while Vermetids have a glossy interior finish.

Habitat and Distribution: Only one species of Serpulid Worms is found in fresh water. All the rest are marine species. They are found attached to coral, rock, and other hard surfaces. They range in depth from the intertidal zone to very deep-sea trenches. They are found worldwide in polar to tropical seas. At least seventy-five species from this family are found in Mexican waters. Some of these species are non-native, invasive species that were introduced to the area by specimens travelling on the hulls of ships or by shrimp farming.

Reproduction: Serpulids may be gonochoric (male or female for life) or hermaphroditic (having both male and female reproductive organs). They may reproduce  asexually by paratomy (budding from the posterior end), or sexually. Sexual reproduction involves broadcast spawning, generally with external fertilization, though some species brood larvae in tubes or special pouches. The fertilized eggs mature to planktonic larvae which settle on to hard substrates and begin tube building. From this point forward, they remain confined to their tube.

Ecosystem Interactions: Serpulids are suspension feeders that filter plankton from the water column by use of their radioles. Once caught, the plankton are swept down a groove, by currents generated by cilia, to the mouth. In turn they are eaten by crabs, fish, gastropods and starfish.  Serpulids are important contributors of calcium to coral reef building; they are also known for being destructive by fouling boat hulls and pipelines.