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

A red seaweed (Catenella caespitosa)

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



A moss-like plant with an irregularly and highly branched frond. The frond is constricted at intervals into different sized segments and the holdfast is a mass of tangled fibres. The plant is small (growing up to 2 cm tall) and is dark purple.

Recorded distribution in Britain and Ireland

Widely distributed and common to rocky shores on all coasts of the UK and Ireland.

Global distribution



It is commonly found on the middle to upper levels of rocky shores, but is restricted to sheltered and shaded conditions. It can also sometimes be found in estuaries. It often grows together Gelidium pusillum, with which it can be confused.

Depth range


Identifying features

  • Small, up to 2 cm tall.
  • Dark purple in colour.
  • Moss-like, with irregularly and highly branched fronds.
  • Frond constricted at intervals.
  • Holdfast a mass of tangled fibres.

Additional information

Can be confused with the lichen Lichina pygmaea but is found in damper and less exposed locations, tends to be lower on the shore, and is composed of small dark purple flattened fronds.

Listed by

- none -

Further information sources

Search on:


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

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

  4. Hiscock, S., 1986b. A field key to the British Red Seaweeds. Taunton: Field Studies Council. [Occasional Publication No.13]

  5. 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.]

  6. McLeod, C.R., Yeo, M., Brown, A.E., Burn, A.J., Hopkins, J.J. & Way, S.F. (ed.), 2002. The Habitats Directive: selection of Special Areas of Conservation in the UK. 2nd edn., 2002-10-04

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

  8. 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.


This review can be cited as:

Pizzolla, P.F 2003. Catenella caespitosa A red seaweed. 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 21-09-2018]. Available from:

Last Updated: 26/06/2003