Cyanea capillata | Lion’s Mane Jellyfish | Smugairle leonmhongach



Conservation status

Ireland: Not considered threatened.  
Europe: Not considered threatened.  
Global: Not considered threatened.

Legal status

Cyanea capillata is not afforded legal protection in Ireland.

Native status



Not assessed

Species Biology


Key identification features include:
•    Large saucer-shaped umbrella divided into 8 lobes with deep clefts in-between
•    Umbrella can be 30 to 80 cm in diameter (sometimes larger)
•    Colour usually yellowish brown or reddish
•    The tentacles are located on the subumbrella surface bell (underneath), some distance away from the umbrella (bell) margin
•    Tentacles are arranged into 8 groups of 70 to 150 tentacles in each group
•    Oral arms are the same length as the diameter of the umbrella and are very membranous and curtain-like
•    The gonads hang freely beneath the umbrella


C. capillata is a coastal northern boreal species. It is a pelagic animal found in surface waters right and throughout the water column. The benthic polyps are found on hard substratum such as rocks but also man-made structures such as pontoons in shallow, sheltered bays.

Source: Russell, 1970

Life cycle

C. capillata reach sexual maturity in the summer. Eggs are fertilized in-situ in female medusae before they are released as free-swimming planulae. These attach to suitable substratum to form polyps called “scyphistoma”. The polyps strobilate and release free-swimming ephyrae which grow into medusae, completing the cycle.

Source: Brewer, 1989; Russell, 1970

Threats faced

This species is not considered threatened or endangered.

Source: Doyle et al., 2014; Omori & Nakano 2001


World distribution(GBIF)

This species has a circumpolar distribution. It occurs in North Atlantic and Pacific waters. It is common in southern parts of the North Sea and regularly occurs in the western half of the Baltic Sea.

Source: Russell, 1970; Sparmann, 2012

Irish distribution

C. capillata is a cold-water species with a marked latitudinal distribution. It is common in the northern half of the Irish Sea, off the north coast of Ireland and down the west coast of Ireland as far as Mayo. In most years it is rarely occurs south of the 53°N latitude parallel. It can be very abundant locally, for example, in Dublin Bay C. capillata is regularly spotted near the Forty Foot bathing spot, around Ireland’s Eye and washes up frequently on the beaches of Counties Meath and Louth. In the Irish Sea highest densities were recorded at 20 to 30 km from the Irish coast. Mostly encountered from June to until late September.

Source: Doyle et al., 2007; Bastian et al., 2011

Temporal change

Records submitted to Data Centre in 2020

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Bastian, T., Haberlin, D., Purcell, J. E., Hays, G. C., Davenport, J., McAllen, R., and Doyle, T. K. (2011). Large-scale sampling reveals the spatio-temporal distributions of the jellyfish Aurelia aurita and Cyanea capillata in the Irish Sea
Brewer, R. H. (1989). The annual pattern of feeding, growth, and sexual reproduction in Cyanea (Cnidaria: Scyphozoa) in the Niantic River estuary, Connecticut. The Biological Bulletin, 176(3), 272-281.

Doyle, T. K., Houghton, J. D., Buckley, S. M., Hays, G. C., & Davenport, J. (2007). The broad-scale distribution of five jellyfish species across a temperate coastal environment. Hydrobiologia, 579(1), 29-39.

Doyle, T. K., Hays, G. C., Harrod, C., & Houghton, J. D. (2014). Ecological and societal benefits of jellyfish. In Jellyfish blooms (pp. 105-127). Springer Netherlands.

Omori, M., & Nakano, E. (2001). Jellyfish fisheries in southeast Asia. In Jellyfish Blooms: Ecological and Societal Importance (pp. 19-26). Springer Netherlands.

Russell, F. S. (1970). The medusae of the British Isles (Vol. 2). CUP Archive.

Sparmann SF (2012) Contributions to the molecular phylogeny, phylogeography, and taxonomy of scyphozoan jellyfish. Dissertation, University of British Columbia.