Sipuncula, the peanut worms, is a group of unsegmented, vermiform, marine coelomates. It is a relatively species poor phylum consisting of about 150 species and subspecies worldwide, closely related to annelids and molluscs. They live at all depths, in a variety of oceanic habitats, within unconsolidated sediments or inside protective shelters, often molluscs shells, polychaeta or foraminiferan tubes.
Sipunculans have two body regions: trunk, the main part of the body and introvert - retractable and eversible narrow, anterior part of the animal, which can be less than half of the trunk in case of some species and more than several times the trunk length of the others.
Though not rich in species the phylum representatives may play a considerable role in the ecosystem. Most sipunculan worms are deposit feeders that settle on various substrata, often on soft bottom. Sipunculans transform particulate food (microalgae, protista, meiofauna, detritus, fecal pellets) from the water column, sediment interface or sediment itself. They are consumed by cephalopods, anemones, crabs, gastropods and fish.
Sipunculans can be active burrowers and their role as bioturbators of the sediments might be important. Sipunculans of Nephasoma genus are producers of deep burrows in the deep-sea sediments. In some areas sipunculans occur in very high densities.
This web presents information on sipunculans occurring in Svalbard waters and deep Nordic Seas.
Class: Sipunculidea E. Cutler and Gibbs, 1985
Order: Goldfingiiformes E. Cutler and Gibbs, 1985
Family: Phascolioniidae E. Cutler and Gibbs, 1985
Often within protective shelter.
Genus: Phascolion Théel, 1875
Epidermal holdfasts Or attachment papillae of ten present.
Anus situated on anterior trunk.
Epidermal attachment papillae absent.
Anus situated on distal half on introvert.
Genus: Nephasoma Pergament, 1940
Two introvert retractor muscles.
Four introvert retractor muscles.
List of Arctic species prepared by Monika Kędra.