Tube Worm

***Ficopomatus enigmaticus***, commonly known as the **Australian tubeworm**, is a species of serpulid tubeworms. Their true native range is unknown, but they probably originated in the Southern Hemisphere, perhaps from the Indian Ocean and the coastal waters of Australia. Today they have a cosmopolitan distribution, having been introduced to shallow waters worldwide. The Australian tubeworm is an invasive species that dominates and alters habitats, reduces water quality, depletes resources, and causes biofouling

## Taxonomy

*Ficopomatus enigmaticus* is classified in the genus *Ficopomatus* in the family Serpulidae. They are polychaetes belonging to the order Canalipalpata, the bristle-footed or fan-head worms. The species was first described by the French zoologist Pierre Fauvel in 1923 as *Mercierella enigmatica*.

## Description

Australian tubeworms are usually about 2 to 2.5 cm (0.79 to 0.98 in) long, and up to 4 cm (1.6 in) at times. On the front end are up to 20 branching gill plumes, which are gray, green, or brown in color. The worms secrete a calcareous tube around themselves, which reaches up to 10 cm (3.9 in) long by 2 cm (0.79 in) wide. The tubes are white and turn brown with age. They are flared at the opening and has flaring rings along their lengths. The mouth can be sealed with a spiny covering (the operculum).

Australian tubeworms always live colonially, with many tubes growing together to form small clusters or large reefs. The aggregations are very dense. There can be up to 180,000 worms per square meter of reef, with the tube openings just about a millimeter apart. The tubes stick together with layers of tiny crystals. The tubes may weave together, and as new worms settle on the outer surface, the reef becomes a solid mass. Reefs of worms can be over 7 m (23 ft) long. When the invasion of Lake of Tunis in Tunisia was at its most severe, the total reef mass of the lagoon was thought to contain about 540,000 tons of carbonate. In shallow water, a reef can be circular in shape as new worms settle along the outer edges. Neighboring reefs may join together to make platforms. In a current, the reef can be elongated.

## Biology

Australian tubeworms are generally found in temperate and subtropical climates. They live in waters up to 3 m (9.8 ft) deep in habitat types such as estuaries and lagoons. They can tolerate a wide range of salinities, and can be found in marine and hypersaline environments, However, they are most common in brackish water. They are sensitive to wave action, and reefs usually grow in protected areas with slow-moving or stagnant water. The larvae are trochophores that drift with the zooplankton and settle onto the substrate after 20 to 25 days. They may build their tubes on established reefs or on beds of rock or shells, rocky or woody debris, reefs of other animals such as oysters, beds of vegetation, structures such as docks, piers, and marinas, or objects such as pilings and boats.

On the coast of South Africa, Australian tubeworms have been observed growing on the aquatic plant *Potamogeton pectinatus*. In Argentina, the larvae settle on shells such as those of the sea snail *Adelomelon brasiliana* and the clams *Mactra isabelleana* and *Tagelus plebeius*. In the Black Sea the reefs are associated with barnacles of the genus *Balanus*, caridean shrimp of the genus *Palaemon*, mud crabs of the genus *Xantho*, amphipods of the genus *Orchestia*, and isopods of the genus *Sphaeroma*. Some tubeworm reefs also have colonies of bryozoans built into them.

They are filter feeders, gathering zooplankton, phytoplankton, and detritus particles from the water and transporting them to their mouths with the cilia on their gill plumes. During their larval stage, they feed on phytoplankton. They reproduce sexually, releasing eggs and sperm into the water during spawning. They are iteroparous, able to produce more than one batch of offspring. They are also protandric hermaphrodites, changing sex from males to females. The older, larger worms in a colony are generally female. Their lifespan is 4 to 8 years