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

Sea chervil (Alcyonidium diaphanum)

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



Alcyonidium diaphanum forms an erect colony that can grow up to 50 cm long but more usually 15 cm. It has a small encrusting base, which attaches to hard substratum. The colour of Alcyonidium diaphanum can be light honey, brown, pale yellowish, grey, reddish, dark mahogany or even colourless. The size, colour and colony form varies widely around the British Isles.

Recorded distribution in Britain and Ireland

Found around all British and Ireland coasts.

Global distribution

Common off all north European coasts.


Alcyonidium diaphanum is found attached to rocks, shells or stones from the lower intertidal zone to shelly sands and coarse grounds offshore.

Depth range


Identifying features

  • Erect colony up to 50 cm high.
  • Surface smooth, occasionally knobbly.
  • Firmly gelatinous.
  • Variable colour; brown, yellow, reddish, grey or colourless.
  • Variable shape and size.

Additional information

Other common names include "curly weed", "amber weed" and ju-ju weed" (Pathmanaban et al., 2005).

Alcyonidium diaphanum is responsible for the allergic contact dermatitis, termed 'Dogger Bank Itch', experienced mostly by fishermen and dock workers (Pathmanaban et al., 2005). Although previously not reported from any other fishing grounds around the British Isles (Hayward, 1985), and despite its name, Dogger Bank Itch has also been reported from trawler-men in le Havre, shell fishermen from Cornwall and fixed net fishermen in the eastern English Channel (Pathmanaban et al., 2005).

Listed by

- none -

Further information sources

Search on:


  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. Hayward, P.J. 1985. Ctenostome Bryozoans. Bath: Pitman Press. [Synopses of the British Fauna, no. 33.]

  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. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  6. Pathmanaban, O.N., Porter, J.S. and White, I.R., 2005. Dogger Bank itch in the eastern English Channel: a newly described geographical distribution of an old problem. Clinical and Experimental Dermatology, 30, 622-626.

  7. 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.

  8. Porter, J.S., Ellis, J.R., Hayward, P.J., Rogers, S.I. & Callaway, R. 2002. Geographic variation in the abundance and morphology of the bryozoan Alcyonidium diaphanum (Ctenostomata: Alcyonidiidae) in UK coastal waters. Journal of the Marine Biological Association of the United Kingdom, 82, 529-535.

  9. Porter, J.S., Hayward, P.J. & Spencer-Jones, M.E. 2001. The identitiy of Alcyonidium diaphanum (Bryozoa: Ctenostomatida). Journal of the Marine Biological Association of the United Kingdom, 81, 1001-1008.


This review can be cited as:

Ager, O.E.D. 2007. Alcyonidium diaphanum Sea chervil. 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. [cited 23-09-2018]. Available from:

Last Updated: 03/07/2007