Biodiversity & Conservation

A horseshoe worm - Phoronis muelleri

A horseshoe worm

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Distribution map

Phoronis muelleri recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Phoronis muelleri is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Phoronida Horseshoe worms
Authority Selys-Longchamps, 1903
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Found all around British coasts and has been recorded off the north-east coast of Ireland.
Habitat information icon Habitat information Phoronis muelleri penetrates vertically into muddy to sandy substrates, often with a high organic content and with an abundance of detritus and suspended material. It can be found from the intertidal zone to a depth of up to 400 m. It is frequently recorded in Macoma and Amphiura communities. Phoronis muelleri occurs in either boring or encrusting forms and may secrete and live in a membranous, cylindrical tube.
Text page icon Description The horseshoe worm Phoronis muelleri is elongated and worm- shaped. The mouth is surrounded by a characteristic horseshoe shaped arangement of tentacles known as the lophophore. Phoronis muelleri can be up to 12 cm in length but less than 1 mm in width. The body is a pinkish colour and the lophophore is transparent, sometimes with spots. The lophophore of Phoronis muelleri sometimes has medially turned ends and the numerous tentacles are notably shorter near the mouth but may reach up to 2 mm in length.
Identifying features
  • Up to 12 cm in length, 1 mm in width.
  • Horseshoe shaped lophophore with short tentacles less than 2 mm in length.
  • Tentacles shorten towards the mouth.
  • No inward fold at the base of the lophophore.
  • The nephridia (kidney-like organ) has only one funnel.
  • Only one giant nerve fiber is present.
Additional information icon Additional information Phoronida have a characteristic ciliated and free-swimming pelagic larva, known as Actinotrocha. Separate names for larval and adult forms may still be used in taxonomy (Emig, 1979).

This review can be cited as follows:

Morvan Barnes 2008. Phoronis muelleri. A horseshoe worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 19/06/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4109>