Grateloup’s pimple weed (Dermocorynus montagnei)

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



Dermocorynus montagnei is a non-coralline crustose alga. It is composed of horizontally expanded crusts and characteristic small erect reproductive papillae that seem randomly scattered over the surface of the crust. Mature papillae may be as much as 2 mm long and 0.5 mm broad. The papillae are not usually branched and are more or less terete and ovate when fully fertile. Depending on their type, the papillae may either be irregular or warty in nature. The crusts of Dermocorynus montagnei are strongly adherent to the substrate and have undulating and slighty irregular outlines. The crusts may be up to 220 µm thick and are generally brownish-red in colour, while the papillae are more purple in colour.

Recorded distribution in Britain and Ireland

Recorded from western Scotland, south-west England, the Welsh coast and a small inlet of Kilkieran Bay, County Galway, Ireland. Possibly under recorded.

Global distribution



Dermocorynus montagnei has been recorded growing as an epilithic crust on small, mobile stones and pebbles in shallow subtidal waters. More rarely has it also been observed growing on detached maerl fragments.

Depth range


Identifying features

  • Usually found on mobile stones and pebbles.
  • Non-coralline crustose alga.
  • Brownish-red crust and purple papillae.
  • Terete and oval papillae.

Additional information

Often confused with red seaweed of the genus Grateloupia, it can best be differentiated by its specific morphology, in particular papillae characteristics. However, much debate still exists as to its taxonomic classification and recent genetic analysis investigating molecular and morphological data has placed Dermocorynus montagnei in a sub-group of Gradeloupia (Wilkes et al., 2005).


  1. Guiry, M.D., Maggs, C.A. 1982. The morphology and the life history of Dermocorynus montagnei Crouan frat. (Halymeniaceae; Rhodophyta) from Ireland. British Phycology Journal, 17, 215-228

  2. Hardy, F.G. & Guiry, M.D., 2003. A check-list and atlas of the seaweeds of Britain and Ireland. London: British Phycological Society

  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.]

  4. Wilkes, R.J., McIvor, L.M. & Guiry, M.D., 2005. Using rbcl sequence data to reassess the taxonomic position of some Grateloupia and Dermocorynus species (Halymeniaceae; Rhodophyta) from the north-eastern Atlantic. European Journal of Phycology, 40, 53-60


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

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-05-28


This review can be cited as:

Barnes, M.K.S. 2008. Dermocorynus montagnei Grateloup’s pimple weed. 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 28-05-2024]. Available from:

Last Updated: 27/03/2008