Lion's Mane Jellyfish

Lion's Mane Jellyfish in shallow waters

James R.D. Scott / Getty Images

Lion's mane jellyfish are beautiful, but an encounter with them can be painful. Here you can learn how to identify a lion's mane jellyfish and how to avoid them.


The lion's mane jellyfish (Cyanea capillata) is the world's largest jellyfish—their bells can be over 8 feet across.

These jellies have a mass of thin tentacles that resemble a lion's mane, which is where their name originates. Reports of tentacle size in lion's mane jellyfish vary from 30 feet to 120 feet—either way, their tentacles extend a long way, and one should give them a very wide berth. This jellyfish also has lots of tentacles—it has 8 groups of them, with 70-150 tentacles in each group.

The color of the lion's mane jellyfish changes as it grows. Small jellyfish under 5 inches in bell size are pink and yellow. Between 5-18 inches in size, the jellyfish is reddish to yellowish-brown, and as they grow past 18 inches, they become a darker reddish brown. Like other jellyfish, they have a short lifespan, so all these color changes may happen in a period of about one year.


  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Scyphozoa
  • Order: Semaeostomeae
  • Family: Cyaneidae
  • Genus: Cyanea
  • species: capillata


Lion's mane jellyfish are found in cooler waters, usually less than 68 degrees F. They may be found in the North Atlantic Ocean, including the Gulf of Maine and off the coasts of Europe, and in the Pacific Ocean.


Lion's mane jellyfish eat plankton, fish, small crustaceans and even other jellyfish. They can spread their long, thin tentacles out like a net and descend into the water column, capturing prey as they go.


Reproduction occurs sexually in the medusa stage (this is the stage you'll picture if you think of a generic jellyfish). Under its bell, the lion's mane jellyfish has 4 ribbon-like gonads which alternate with 4 very folded lips. The lion's mane jellyfish has separate sexes. The eggs are held by oral tentacles and are fertilized by sperm. Larvae called planula develop and settle on the ocean bottom, where they develop into polyps.

Once in the polyp stage, reproduction can occur asexually as polyps divide into disks. As the disks stack up, the uppermost disk swims away as an ephyra, which develops into the medusa stage.


  • Bryner, Jeanna. 2010. How One Jellyfish Stung 100 People. MSNBC.
  • Cornelius, P. 2011. Cyanea Capillata (Linnaeus, 1758). Accessed through: World Register of Marine Species. 
  • Encyclopedia of Life. Cyanea Capillata. 
  • Heard, J. 2005. Cyanea Capillata, Lion's Mane Jellyfish. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Plymouth: Marine Biological Association of the United Kingdom.
  • Meinkoth, N.A. 1981. National Audubon Society Field Guide to North American Seashore Creatures. Alfred A. Knopf, New York.
  • WoRMS. 2010. Porpita Porpita (Linnaeus, 1758). In: Schuchert, P. World Hydrozoa database.
mla apa chicago
Your Citation
Kennedy, Jennifer. "Lion's Mane Jellyfish." ThoughtCo, Aug. 17, 2021, Kennedy, Jennifer. (2021, August 17). Lion's Mane Jellyfish. Retrieved from Kennedy, Jennifer. "Lion's Mane Jellyfish." ThoughtCo. (accessed March 27, 2023).