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

Lion's mane jellyfish (Cyanea capillata)

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



Cyanea capillata is one of the largest species of jellyfish and is commonly referred to as Lions mane jellyfish due to the highly distinguishable mass of long, thin, hair-like tentacles. Cyanea capillata has a saucer-shaped bell (the umbrella) with a uniform thickness until thinning dramatically around the edges. Usually yellowish brown or reddish in colour. It generally grows to 30-50 cm in diameter in British waters. However, they have been know to grow up to 200 cm. The margin of the bell bears hollow tentacles, arranged in eight groups with 70 to 150 or more tentacles in each. The mouth and oral arms stem from a projection on the underside of the umbrella (the manubrium). The oral arms are thick, frilled, folded and generally as long as the diameter of the umbrella.

Recorded distribution in Britain and Ireland

Found around the coasts of the British Isles, most commonly along the east coast of England and Scotland. Also common in the Irish Sea.

Global distribution



Cyanea capillata is pelagic species that can be found washed up on beaches.

Depth range


Identifying features

  • Cyanea capillata has a diameter 30 cm or more.
  • Usually yellow brown or red in colour.
  • It is easily distinguished by a mass of long, hair-like tentacles.
  • There at least 65 tentacles in each of the eight groups of tentacles.

Additional information

Young Cyanea capillata may be found as early as February in British waters, although the main period of abundance for larger individuals is June to September. This species does occasionally occur in large swarms, largely thought to be due to storms and tides that concentrate individuals together (Russell, 1970). They have a very severe sting that can produce blisters, irritation, and muscular cramp and may even affect respiratory and heart function. Cyanea capillata can still sting long after being stranded on the shore.

Listed by

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Further information sources

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  1. Hayward, P.J. & Ryland, J.S. (ed.) 1995a. The marine fauna of the British Isles and north-west Europe. Volume 2. Molluscs to Chordates. Oxford Science Publications. Oxford: Clarendon Press.

  2. 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.]

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

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

  5. 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.

  6. Russell, F.S., 1970. The medusae of the British Isles. Vol II - Pelagic Scyphozoa, with a supplement to the first volume on hydromedusae. Cambridge University Press


This review can be cited as:

Heard, J.R. 2005. Cyanea capillata Lion's mane jellyfish. 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 24-09-2018]. Available from:

Last Updated: 03/05/2005