Phascolion strombus (Montagu, 1804)
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.
Common trunk length: 5-15 mm.
Maximum trunk length: 30-40 mm.
Grey, brown, yellowish, reddish.
Inhabits sand, mud, silt, often found in mollusk shells and polychaete tubes.
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.
Very common and eurytopic in the Arctic oceans; known from depths of 1 - 4030 m.