This web site was created within Arctic Ocean Diversity (ArcOD) project
and was financially supported by Polish Ministry of Science (project number: DPN/N63/AODP/2009).

Phascolion strombus strombus (Montagu, 1804)

A cosmopolitan species often found in mollusk shells and polychaete tubes

Phascolion strombus

Phascolion strombus: papillae
Sipunculus strombus Montagu, 1804
Phascolion strombi Théel, 1875

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.

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

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.

Very common and eurytopic in the North Atlantic and Arctic oceans; known from depths of 1 - 4030 m.