Biodiversity & Conservation

Sea chervil - Alcyonidium diaphanum

Alcyonidium diaphanum

Image Keith Hiscock - Dense growth of Alcyonidium diaphanum colonies at about 3 metres depth. Image width ca 15 cm.
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Distribution map

Alcyonidium diaphanum recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Alcyonidium diaphanum is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Bryozoa Sea mats, horn wrack & lace corals
Class Gymnolaemata
Authority (Hudson, 1762)
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Found around all British and Ireland coasts.
Habitat information icon Habitat information Alcyonidium diaphanum is found attached to rocks, shells or stones from the lower intertidal zone to shelly sands and coarse grounds offshore.
Text page icon Description 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.
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 icon 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).

This review can be cited as follows:

Olwen Ager 2007. Alcyonidium diaphanum. Sea chervil. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 24/05/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=2437>