A fanworm (Acromegalomma vesiculosum)

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



Acromegalomma vesiculosum is a polychaete worm that reaches up to 12 cm in length. It has relatively few (about 50) tentacles, each with a large eyespot at the free end. It creates a long and tough tube, which is mostly encrusted untidily with large shell fragments and small stones. The tube protudes no more than 2-3 cm from coarse sand or muddy gravel at low water and below. The body and crown vary in colour from yellowish to a reddish-purple brown and is usually spotted.

Recorded distribution in Britain and Ireland

Recorded from several locations off the west coasts of Scotland, south-west England, Wales and Ireland.

Global distribution



Found in mud with stones and sand; lower shore and sublittoral in sheltered bays; sometimes amongst seagrasses.

Depth range


Identifying features

  • Tubeworm up to 12 cm in length,
  • Short abdominal tori.
  • Abdomen is longer than thorax.
  • Short transverse rows of abdominal chaetae.
  • Distinct collar is fused to mid-dorsal groove.
  • Up to 30 spines either side; each with a compound, bulbous, blackish-brown eye.

Additional information

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Listed by

- none -


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

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

  3. 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.]


  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-21


This review can be cited as:

Ruiz, A. 2007. Acromegalomma vesiculosum A fanworm. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-07-2024]. Available from: https://marlin.ac.uk/species/detail/2167

Last Updated: 04/09/2007