Club-headed hydroid (Clava multicornis)

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



This colonial hydroid can appear in two forms either as a diffuse network of stolons with scattered polyps or as a dense mat of stolons with many polyps. The stolon is thread-like and the polyps rise directly from it growing up to 25 mm in height. The polyps have 30 to 40 tentacles and have reproductive bodies clustered on short branches below the tentacles. The polyps are pink, white or red. The physical form of the colony is variable and thought to be determined by a range of environmental factors such as substratum type, tidal exposure, food availability and water movement.

Recorded distribution in Britain and Ireland

Found around the north, west and southern coasts of Britain and Ireland.

Global distribution



This hydroid is found on middle to lower shore, mainly as an epiphyte growing on fucoid algae, such as Fucus vesiculosus, Fucus serratus and Ascophyllum nodosum. Clava multicornis can also be found on rocks or shells and in rock pools and is tolerant of brackish waters.

Depth range


Identifying features

  • Occurs in two forms: diffuse or dense networks of stolons.
  • Stolon thread-like with polyps rising directly from it.
  • Polyps pink, white or red.
  • Polyps up to 25 mm in height.
  • Found mainly growing on fucoid algae.

Additional information

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Listed by

- none -


  1. Bruce, J.R., Colman, J.S. & Jones, N.S., 1963. Marine fauna of the Isle of Man. Liverpool: Liverpool University Press.

  2. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

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

  4. 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.]

  5. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  6. 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.


  1. Bristol Regional Environmental Records Centre, 2017. BRERC species records recorded over 15 years ago. Occurrence dataset: accessed via on 2018-09-25.

  2. Centre for Environmental Data and Recording, 2018. Ulster Museum Marine Surveys of Northern Ireland Coastal Waters. Occurrence dataset accessed via on 2018-09-25.

  3. Fenwick, 2018. Aphotomarine. Occurrence dataset Accessed via on 2018-10-01

  4. NBN (National Biodiversity Network) Atlas. Available from:

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


This review can be cited as:

Pizzolla, P.F 2002. Clava multicornis Club-headed hydroid. 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:

Last Updated: 11/10/2002