Phascolion strombus (Montagu, 1804)
Descriptions
Ventral retractor much thinner then dorsal. Holdfast papillae V-shaped with dark hardened border. Sharp, clawlike hooks. 10-30 well-deweloped tentacles present on the introvert. An aggregation of large papillae around the anterior end of the trunk. Trunk length 30-40 mm (usually 5-20mm).
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.
Sources
Cutler, E.B. (1994) The Sipuncula. Their Systematics, Biology, and Evolution. New York: Cornell University Press.
Cutler, E.B.; Cutler, N.J. (1985) A revision of the genera Phascolion, Théel, and Onchnesoma Koren and Danielssen (Sipuncula). Proceedings of the Biological Society of Washington 98:809-850
Kędra, M.; Murina, G.V. (2007) The sipunculan fauna of Svalbard. Polar Research 26:37-47
Kędra, M.; Murina, G.V. (2007) The sipunculan fauna of Svalbard. Polar Research 26:37-47
Distribution
Ecology
Semimobile, mostly epibenthic worm 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 and determined by the sediment type (Hylleberg 1975).
It avoids soft clay as the irrigation than is impossible due to clogging of the apertures (Hylleberg 1975).
Mostly epibenthic worm holding empty shells and tubes. It inhabits the shells of gastropods and scaphopods or may live freely.
