Biodiversity & Conservation

A horseshoe worm - Phoronis hippocrepia

Phoronis hippocrepia

Image Keith Hiscock - Horseshoe worm, Phoronis hippocrepia in limestone. Image width ca 5cm.
Image copyright information

  • #
  • #
  • #
  • #
Distribution map

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

Why do the maps differ?

Sightings Have you seen Phoronis hippocrepia?
If so please submit your record.

Phoronis hippocrepia is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Phoronida Horseshoe worms
Authority Wright, 1856
Recent synonyms Larva originally described as Actinotropha hippocrepia Silén, 1954.
Map icon Recorded Distribution in Britain and Ireland Found on all British and Irish coasts, especially common where rock is limestone.
Habitat information icon Habitat information 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.
Text page icon 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.
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 icon 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).

This review can be cited as follows:

Susie Ballerstedt 2006. Phoronis hippocrepia. 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=4108>