Sipuncula (Unsegmented Marine Worms)


Sipuncula is a phylum of unsegmented marine worms with a retractable introvert and a gut that is wound back on itself to an anus at the anterior end of the trunk.

Keywords: peanut worms; minor phylum; benthos

Figure 1.

Sipunculan external form showing variation within the genus Themiste. Broad trunk, with more slender retractable introvert, and terminal tentacles.

Figure 2.

Internal organs of stylized sipunculan. Variation among taxa includes number of retractor muscles, arrangement of spindle muscle, nature of body wall muscle layers, and number/size of nephridia.


Further Reading

Cutler EB (1994) The Sipuncula, their Systematics, Biology and Evolution. Ithaca, NY: Cornell University Press.

Cutler EB and Cutler NJ (1987) Deep‐water Sipuncula from the eastern Atlantic Ocean. Sarsia 72: 71–89.

Cutler EB and Gibbs PE (1985) A phylogenetic analysis of higher taxa in the phylum Sipuncula. Systematic Zoology 34: 162–173.

Rice ME (1983) Sipuncula. In: Adiyodi KG and Adiyodi RG (eds) Reproductive Biology of Invertebrates: Oogenesis, Oviposition and Oosorption, pp. 283–296. New York: John Wiley and Sons.

Rice ME (1993) Sipuncula. In: Harrison FW and Rice ME (eds) Microscopic Anatomy of Invertebrates, vol. 12: Onychophora, Chilopoda, and Lesser Protostomata, pp. 238–325. New York: Wiley‐Liss.

Scheltema AH (1993) Aplacophora as progenetic aculiferans and the coelomate origin of mollusks as the sister taxon of Sipuncula. Biological Bulletin (Woods Hole) 184(1): 57–78.

Stephen AC and Edmonds SJ (1972) The Phyla Sipuncula and Echiura. London: Trustees of the British Museum (Natural History).

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How to Cite close
Cutler, Edward B(Apr 2001) Sipuncula (Unsegmented Marine Worms). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001600]