Lion's mane jellyfish (Cyanea capillata)
|Size||Bell diameter: up to 2 m (2)|
Tentacle length: up to 60 m (3)
Maximum weight: over 1 tonne (4)
- The lion’s mane jellyfish can grow to over 2 m wide and its tentacles can be up to 60 m long.
- The lion’s mane jellyfish is the largest jellyfish in the Atlantic Ocean.
- As with all jellyfish, the mouth of the lion’s mane jellyfish is located on the underside of the bell-shaped body.
- The lion’s mane jellyfish is often bioluminescent, emitting its own light.
- Even when the tentacles of the lion’s mane jellyfish are detached within the water, they are still able to sting a human.
The lion’s mane jellyfish has yet to be assessed by the IUCN.
The lion’s mane jellyfish (Cyanea capillata) is one of the largest jellyfish in the world. It gains its common name from the characteristic mass of long, thin, hair-like tentacles found hanging from the underside of the bell-shaped body (2). The tentacles are hollow and are arranged in 8 groups of between 70 and 150 (2) (5). The mouth of the lion’s mane jellyfish is also located on the underside of the bell, in the middle of the tentacles, and is surrounded by four thick, frilled, folded ‘oral arms’, which are shorter than the tentacles (2) (3) (5) and are dark red or red-brown (3) (6).
The smooth, saucer-shaped bell of the lion’s mane jellyfish is relatively flat and can vary in colouration between yellow, brown and red (2) (3) (5). The edges of the bell are thinner than the thick centre (6) and are pale yellow (3).
The lion’s mane jellyfish is often bioluminescent, meaning it produces its own light, making it glow in dark waters (4).
The juvenile lion’s mane jellyfish has pale pink, yellow or colourless oral arms, which become dark red as the individual ages (3) (6).
The lion’s mane jellyfish has a global distribution (3) (7), although it is mostly found in the northern hemisphere in the North Atlantic, North Pacific and North Sea (4) (5), as well as around Australia in the south (4).
A pelagic species, the lion’s mane jellyfish is found in open ocean (2) (4). It is not present in brackish water as it requires areas with higher salinity (8).
The lion’s mane jellyfish and its larvae prey on zooplankton, small fishes and other jellyfish (4) (5) (7), including the common jellyfish (Aurelia aurita) (3). It is known to catch prey with the powerful stings on its tentacles (5).
As with all jellyfish, the lion’s mane jellyfish produces eggs and sperm on gonads within the digestive cavity, with fertilisation occurring after the eggs and sperm have been dispersed into the water. The resulting larvae then settle on the seabed and a small polyp begins to grow. After a period of development, multiple medusae are released from each polyp, dispersing through the sea and eventually growing into sexually mature adults (9) (10). Small medusae are most abundant between April and May and are mostly seen at the surface of the water (6). Mature individuals are mostly seen between June and September on the surface of the water and occasionally occur in large swarms (2) (6).
There are not currently known to be any major threats to the lion’s mane jellyfish.
There are not known to be any specific conservation measures currently in place for the lion’s mane jellyfish.
Find out more about the lion’s mane jellyfish:
Heard, J. (2005) Cyanea capillata. Lion's Mane Jellyfish. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Marine Biological Association of the United Kingdom, Plymouth. Available at:
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- Brackish: slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.
- Fertilisation: the fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
- Gonads: the part of the reproductive system that produces and releases gametes, either eggs or sperm.
- Larva: immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
- Medusa: the sexually mature, free-swimming stage of a jellyfish’s life, which resembles an umbrella or bell with stinging tentacles around the edge.
- Pelagic: relating to or inhabiting the open ocean.
- Polyp: typically sedentary soft-bodied component of Cnidaria, a group of simple aquatic animals including the sea anemones, corals and jellyfish. A polyp comprises a trunk that is fixed at the base, and a mouth that is placed at the opposite end of the trunk and is surrounded by tentacles.
- Zooplankton: tiny aquatic animals that drift with currents or swim weakly in water.
Integrated Taxonomic Information System (ITIS) (July, 2012)
Heard, J. (2005) Cyanea capillata. Lion's Mane Jellyfish. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Marine Biological Association of the United Kingdom, Plymouth Available at:
- Johnson, W.S. and Allen, D.M. (2005) Zooplankton of the Atlantic and Gulf Coasts:A Guide to Their Identification and Ecology. Johns Hopkins University Press, Maryland.
- Nellis, D.W. (1997) Poisonous Plants and Animals of Florida and the Caribbean. Pineapple Press, Florida.
- Fish, J.D. and Fish, S. (2011) A Student’s Guide to the Seashore. Cambridge University Press, Cambridge.
Marine Species Identification Portal - Cyanea capillata (July, 2012)
- Purcell, J.E. (2003) Predation on zooplankton by large jellyfish, Aurelia labiata, Cyanea capillata and Aequorea aequorea, in Prince William Sound, Alaska. Marine Ecology Progress Series, 246: 137-152.
- Båmstedt, U., Ishii, H. and Martilnussen, M.B. (1997) Is the scyphomedusa Cyanea capillata (L.) dependent on gelatinous prey for its early development? Sarsia, 82: 269-273.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.
- Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.