MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

A horseshoe worm (Phoronis hippocrepia)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

Phoronis hippocrepia secretes and lives in a membranous, cylindrical tube, and occur in either boring or encrusting forms. Individuals are 0.3-1.5 mm in diameter and can grow up to 10 cm in height, although more commonly attain 4 cm. The body is cylindrical and elongate with a slender trunk (metasome) and a bulbous posterior (ampulla). Tentacles (terminal lophophore) occur entirely on the 'head' region, numbering 50-150. The tentacles are 2-3 mm in length and are arranged in a 'horse-shoe' shape. Individuals are translucent white greenish grey, yellowish or fleshy in colour.

Recorded distribution in Britain and Ireland

Found on all British and Irish coasts, especially common where rock is limestone.

Global distribution

Known in Hawaii, west coast of Panama, Mexico, Brazil, France, Belgium, German, Sweden, Italy and South Africa.

Habitat

Recorded from the intertidal zone near low tide mark to a maximum depth of 48 m. Both boring and encrusting forms inhabit similar substrata: rock, empty mollusc shells, coral skeletons, encrusting coralline algae and wood, although this species is commonly associated with calcareous substrata. Phoronis hippocrepia generally occurs under poor light conditions.

Depth range

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Identifying features

  • Burrowing or encrusting worms within membranous, cylindrical tubes.
  • Body up to 10 cm in length.
  • Between 50-150 tentacles on the 'head' region.
  • Tentacles 2-3 mm long and arranged in a 'horse-shoe' shape.
  • Greenish grey, yellowish or fleshy in colour.
  • The nephridia (kidney-like organ) has two long tubes and two giant nerves on either side.

Additional information

Phoronis hippocrepia can occur in densities of more than 20,000 individuals/m². Identification on this species may require microscopic work and dissection (see Emig, 1979). The only other known genus in this phylum is Phoronopsis. The genus Phoronis can be distinguished from Phoronopsis by the absence of a collar-fold below the lophophore (see Emig, 1979).

Listed by

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Further information sources

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Bibliography

  1. Emig, C.C., 1979. British and other phoronids. London, Academic Press

  2. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  3. Hayward, P.J. & Ryland, J.S. (ed.) 1995a. The marine fauna of the British Isles and north-west Europe. Volume 2. Molluscs to Chordates. Oxford Science Publications. Oxford: Clarendon Press.

  4. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  5. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  6. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid

  7. National Biodiversity Network (NBN) Atlas website. Available from: http://www.nbnatlas.org.  Accessed 01 April 2017

  8. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin., http://www.itsligo.ie/biomar/

Citation

This review can be cited as:

Ballerstedt, S. 2006. Phoronis hippocrepia A horseshoe worm. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1875

Last Updated: 05/12/2006