Mediterranean Fan Worm
(Sabella spallanzanii)

Description: This giant fan worm can attain a length of 40 cm in just a few years of growth. The worm is enclosed in a hard tube (about 1 cm diameter) that is attached to hard surfaces such as rocks, pilings, shells, and even mats of sea grass. When its feeding tentacles are extended, the worm resembles a feathery palm tree. The colors of the tentacles range from white to orange, and may bear banding patterns across the tentacles. When it is disturbed, the worm retracts its tentacles into the tube and rolls up the end.

Habitat: The fan worm is generally found in shallow subtidal areas of protected bays and harbors to depth of 30 m (in contrast, our native fan worms are rarely found in estuarine conditions). They readily form large, dense mats of individuals and quickly outnumber their neighbors.

Origin: European Atlantic and Mediterranean coasts, Azores.

Invaded Areas: Atlantic coast of South America, Java, southeast Australia.

Concerns: Because this voracious suspension feeder rapidly carpets large areas, it has the ability to directly compete with native species for both food and space. It may also interfere with colonization of natives by predation on settling larvae. In Australia, the fan worm has been observed to rapidly colonize areas of seagrass dieback, interfering with normal succession by native plants and animals and preventing seagrass recovery. The presence of a toxin in fan worm tissue may prevent native predators from controlling invasive populations.