Phascolion strombus (Montagu, 1804)

Distinguishing characteristics Two retractors: ventral retractor much thinner then dorsal. Holdfast papillae V-shaped with dark hardened border. Sharp, clawlike hooks. 10-30 well-developed tentacles present on the introvert. An aggregation of large papillae around the anterior end of the trunk. Trunk length 30-40 mm (usually 5-20 mm). Some worms lack hooks, probably due to predation and regeneration of introvert. There is an extreme plasticity of form of this very widespread and common species. Size Common trunk length: 5-15 mm. Maximum trunk length: 30-40 mm. Color Grey, brown, yellowish, reddish. Habitat Inhabits sand, mud, silt, often found in mollusk shells and polychaete tubes. Feeding Deposit feeder. Life cycle Freely spawn gametes into the water. A short-term lecithotrophic trochophore larva. Usually, after settlement they do not disperse a lot. More Biology & Ecology Phascolion strombus uses empty mollusc shells, polychaete tubes and foraminiferan tests as a shelter. They are semimobile, mostly epibenthic worms holding empty shells and tubes and collecting sediments with tentacles. The density of this ecological group tends to be limited by a number of available empty shells and tubes. Its distribution is determined by the sediment type: it avoids soft clay as the irrigation than is impossible due to clogging of the apertures. Distribution Very common and eurytopic in the Arctic oceans; known from depths of 1 - 4030 m.