Sipuncula - peanut worms

Description

Sipuncula [photo: M. Marmach]

Sipuncula: Phascalosoma arcuatum [illustrator: Damon Kowarsky]

Unsegmented marine worms lacking chaetae. The body is divided into a trunk and a slender, retractable introvert. The mouth is located at the tip of the introvert and in some taxa is surrounded by tentacles (not usually seen without narcotisation of live specimens or dissection). The surface of the body usually has a distinctively "leathery" texture and is often covered with warts or papillae. The long gut is typically coiled in a tight helix - if this is visibile it is a distinctive clue allowing quick recognition as a sipunculan. The anus is not terminal, but is located on the side of the trunk.

Comments

Sipunculans are only found in marine environments, where they are found in a variety of substrates including soft sediments, among mussels and oysters, and in algal holdfasts. They also occur as inhabitants of dead gastropod shells and as borers in calcium carbonate substrates including living corals and limestone reefs. About 150 sipunculan species are known world wide, and 57 species are recorded from Australian waters.

Identification of sipunculans requires dissection, and is greatly facilitated if the specimen is narcotised before preservation. There have been a number of thorough systematic studies of sipunculans. Edmonds (1980) is a comprehensive guide to the identification of Australian sipunculans, while Edmonds (1982) describes 14 species occurring in southern Australia. An updated review of the Australian fauna is provided by Edmonds (2000). Stephen and Edmonds (1972) and the more up to date Cutler (1994) review the Sipuncula globally. Each of these publications describes study methods. Edgar (2000) has photographs of two Australian species of Phascolosoma.

References

Cutler, EB. 1994. The Sipuncula - their systematics, biology and evolution. Comstock Publishing Associates, Ithaca.

Cutler, EB and Gibbs, PE. 1985. A phylogenetic analysis of higher taxa in the phylum Sipunculida. Systematic Zoology 34, 162-173.

Edgar, GJ. 2000. Australian Marine Life. Reed, Kew, Victoria.

Edmonds, SJ. 1980. A revision of the systematics of Australian sipunculans (Sipuncula). Records of the Australian Museum 18, 1-74.

Edmonds, SJ. 1982. Sipunculans (Phylum Sipuncula). In Shepherd, SA and Thomas, IM (eds). Marine Invertebrates of Southern Australia Part 1. Handbooks Committee of the South Australian Government, Adelaide, pp. 299-311.

Edmonds, SJ. 2000. Phylum Sipuncula. In Beesley, PL, Ross, GJB and Glasby, CJ (eds). Polychaetes and Allies: the Southern Synthesis. CSIRO Publishing, Melbourne, pp. 375-400.

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