Animal
Lion's mane jellyfish
The lion's mane jellyfish is a big jelly that lives in cold seas. It has lots and lots of long, thin tentacles, like hair.
The lion's mane jellyfish is one of the biggest jellyfish in the world. Its bell is usually 30 to 50 centimeters across, but in very cold seas it can grow to about 2 meters, and hundreds of long, hair-like tentacles trail beneath it to catch food.
Cyanea capillata is a scyphozoan of Arctic and northern boreal coastal seas in the Atlantic and Pacific. Bell size rises with latitude, from about 50 cm in temperate waters to about 2 m in the far north, with eight clusters of up to 150 tentacles. Like other true jellies it alternates between a polyp and a medusa, and its sting is painful.
Photo: Arnstein Rønning, CC BY 3.0, via Wikimedia Commons
Meet the lion's mane jellyfish
The lion's mane jellyfish is a big, soft jelly.
It has a round top called a bell. Under the bell hang lots of long, thin tentacles, like a lion's furry mane. It drifts in cold seas.
The lion's mane jellyfish gets its name from its mass of long, thin tentacles, which can look like the shaggy mane around a lion's head. Its bell is often yellowish brown or reddish.
It is one of the largest jellyfish in the world. The Aquarium of the Pacific calls it the largest of the true jellies, the group that includes moon jellies. It is soft and made mostly of jelly, yet it is a skilled hunter that stalks its prey.
Cyanea capillata (Linnaeus, 1758) is a scyphozoan, or true jelly, in the family Cyaneidae. MarLIN describes it as one of the largest jellyfish species, and the Aquarium of the Pacific calls it the largest of the more than 200 species of Scyphozoa. The genus name comes from the Greek kyanos, dark blue, and capillata from the Latin for hair.
Size depends strongly on where it lives. Walla Walla University's invertebrate guide gives bells up to 2 meters across at high latitudes but usually closer to 50 centimeters farther south, and MarLIN gives 30 to 50 centimeters as usual in British waters, with some reaching 200 centimeters.
Quick facts
- Group
- Invertebrate
- Length
- 30 to 50 cm
- Lifespan in the wild
- up to 1 years
Where it lives
Lion's mane jellies live in cold seas in the north.
They drift near the top of the water, close to the coast. Sometimes waves wash them onto beaches.
Lion's mane jellyfish live in cold and cool seas of the far north: the Arctic Ocean and the northern Atlantic and Pacific Oceans. They drift near the surface, often close to the coast.
In the Pacific they are common as far south as Washington State. In the Atlantic they reach as far south as Florida and Mexico. Along the southeastern coast of the United States they show up only in the colder months, which is why some people call them winter jellies. Around Britain the biggest ones are most common from June to September.
Walla Walla University's guide gives the range as Arctic and north boreal: common in the Pacific south to Washington, occasionally Oregon, probably not California, and in the Atlantic south to Florida and Mexico. The Aquarium of the Pacific adds the Baltic Sea and some Japanese and Chinese waters. The map shades the Arctic, Atlantic and Pacific Oceans; the species lives only in their northern, cooler parts.
It is pelagic, living near the surface in polar and temperate coastal water. Timing varies: off the southeastern United States it appears from late December or January and is gone by mid-May, while in the Arctic, the Pacific Northwest and the northeast Atlantic it is most abundant in late summer. In British waters MarLIN reports young ones from February and larger ones mostly June to September.
Its habitat
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Arctic and cool northern coastal seas: in the Pacific south to about Washington State, in the Atlantic south to Florida and Mexico (mostly in winter), plus the Baltic Sea and some Japanese and Chinese waters. Shading is by ocean; it lives only in their northern, cooler parts.
Places: Arctic Ocean, Atlantic Ocean and Pacific Ocean.
Source: https://inverts.wallawalla.edu/Cnidaria/Class-Scyphozoa/Order-Semaeostomeae/Fami · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Norway, Canada, UK, Sweden, Netherlands, Denmark, Ireland, Germany and 19 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
A jelly that eats jellies
Lion's mane jellies catch small fish, tiny shrimp-like animals and other jellies.
Their sticky tentacles grab the food. Then the jelly pulls it up to its mouth.
The lion's mane jellyfish is a carnivore. It eats fish eggs and baby fish, small fish, tiny crustaceans such as copepods, and other jellyfish, especially moon jellies.
When a tentacle touches food, tiny stinging cells fire and stop the prey from moving. The tentacle then bends toward one of the frilly oral arms under the bell, which grabs the food and moves it toward the mouth. If a meal is too big, like a large moon jelly, the jelly starts digesting it right on its oral arms.
The Aquarium of the Pacific lists fish larvae and eggs, small crustaceans, small fishes, copepods and other jellies, especially moon jellies. When the sticky tentacles touch prey, nematocysts fire and paralyze it; the tentacles contract toward the nearest oral arm, which grasps the food in mucus and passes it along the oral-arm groove to the manubrium and stomach.
Prey too large for the gastric cavity, such as a mature moon jelly, is digested on the oral arms, and the oral arms can also fire nematocysts to collect food directly. The oral arms are thick, frilled and folded and generally about as long as the bell is wide (MarLIN).
Did you know?
Leatherback sea turtles eat lion's mane jellies.
Leatherback turtles eat lion's manes and brush off the stinging cells with their flippers between bites.
Leatherbacks tolerate the nematocysts except near their eyes; how they gain energy from such a watery prey is not known.
A bell and a mane
The bell is soft and round, with wavy edges.
Under it hang hundreds of thin tentacles. The tentacles can be much longer than you are tall.
The bell is shaped like a saucer, thick in the middle and thin at the edge. Its edge is divided into 16 lobes, which come in 8 pairs. When the jelly finishes a swimming stroke, it can look like an eight-pointed star.
The tentacles hang in 8 groups, with up to about 150 tentacles in each group. In large lion's manes they can trail down as far as 9 meters, about as long as two cars parked end to end. Their color can be deep red, purple, pink or even milky white, and young ones are more yellowish brown.
Walla Walla University's guide describes a saucer-shaped bell with a thick center and thin margin divided into 8 pairs of lobes (16 in all), 8 rhopalia (sense organs) set between the lobes of each pair, and 8 horseshoe-shaped clusters of tentacles under the bell, up to 150 each; MarLIN gives 70 to 150 or more per group. Tentacles may trail to about 9 meters in large specimens and about 2 meters in 50-centimeter bells.
The oral arms form a frilly mass about as long as the bell is wide, and four ribbon-like gonads alternate with them. Color runs from brick red and purple to rose, violet or milky white, often yellowish brown in small animals and redder in large ones.
From polyp to jelly
A lion's mane starts as a tiny swimming baby.
The baby sticks to a rock and grows into a polyp. The polyp makes little baby jellies, stacked like plates. They swim away and grow big.
Lion's mane jellyfish have two stages in their life. The female keeps her fertilized eggs on the folds of her oral arms until they become tiny swimming larvae called planulae. A planula swims for a few hours or a few days, then sticks to a shady, rough surface.
There it grows into a polyp, a small tube with tentacles. When conditions are right, the polyp grows a stack of tiny jellies, like a pile of dinner plates. One by one they break off as baby jellies called ephyrae and grow into adults. Adult jellies are thought to live about a year, but polyps can live for many years.
The Aquarium of the Pacific describes the cycle: males release sperm, eggs are fertilized in the female's gonads and brooded on the folded margins of her oral arms until they become ciliated planulae. These swim for a few hours to several days before settling on a shaded, rough surface and developing into polyps called scyphistomae.
In poor conditions the polyps bud off clones; in good conditions they strobilate, forming a stack of disks that are released one at a time as ephyrae, which grow into medusae. Most adult medusae are believed to live about one year, and Walla Walla University's guide says probably less; the polyp stage can live for many years.
Friends among the tentacles
Some little fish hide among the lion's mane tentacles.
The tentacles help keep them safe. Big sea turtles like to eat lion's mane jellies.
A lion's mane jellyfish is like a moving home for other animals. Young walleye pollock, a kind of fish, dart in among its tentacles when danger comes, and some butterfish ride along with the jelly while nibbling on its bell. Tiny young crabs sometimes ride on top of the bell too.
Lion's manes sometimes gather in huge groups called swarms. Scientists think storms and tides push them together. Leatherback sea turtles eat lion's manes, brushing off the stinging cells with their flippers between bites.
The Aquarium of the Pacific lists juvenile walleye pollock sheltering among the tentacles, butterfish riding the jelly and nibbling its bell, and whiting using it for shelter, while a nudibranch eats its polyps. Walla Walla University's guide notes juvenile pollock, other fish and crab megalops larvae riding on the bell.
MarLIN reports occasional large swarms, thought to be due mainly to storms and tides concentrating individuals. Leatherback turtles prey on lion's manes; they seem to tolerate the stinging cells except around their eyes and brush them off with their flippers between bites. How they gain enough energy from such a watery food is not known.
Did you know?
Lion's manes like to eat other jellies.
Lion's mane jellyfish eat other jellies, especially moon jellies. A big moon jelly is digested right on the lion's mane's oral arms.
Moon jellies are a favored prey; prey too large for the gastric cavity is digested on the oral arms (Aquarium of the Pacific).
Safe at sea, and safe for you
There are lots of lion's mane jellies. They are not in danger.
Their tentacles can sting. If you see one in the sea or on the beach, look but do not touch. Tell a grown-up.
The lion's mane jellyfish has not been assessed for the IUCN Red List, and the Aquarium of the Pacific calls it safe for now. Changes in sea temperature may change where it lives and when it breeds, because sea temperature helps trigger its movements.
Its sting is painful. Even a lion's mane that has washed up on a beach can still sting, so the safe rule is to look with your eyes and never touch, and to tell a grown-up if you see one.
Cyanea capillata has not been evaluated for the IUCN Red List (GBIF's Red List copy: Not Evaluated); the Aquarium of the Pacific rates it Safe for Now and suggests that changing sea temperatures may affect its range and reproduction.
MarLIN describes a very severe sting that can cause blisters, irritation and muscle cramps and may affect breathing and heart function, and notes that stranded animals can still sting long afterward. Walla Walla University's guide calls the sting painful, with blisters lasting several hours, and warns that it may even trigger allergic shock; the Aquarium of the Pacific says the sting is not life-threatening unless a person is sensitive to the toxin. Look, don't touch.
Did you know?
A swimming lion's mane can look like a star.
At the end of each swimming stroke, a lion's mane can look like an eight-pointed star.
The 8 pairs of lobes give the contracted bell the look of an 8-pointed star at the end of the power stroke (Walla Walla University).
Amazing facts
-
Lion's manes like to eat other jellies.
Lion's mane jellyfish eat other jellies, especially moon jellies. A big moon jelly is digested right on the lion's mane's oral arms.
Moon jellies are a favored prey; prey too large for the gastric cavity is digested on the oral arms (Aquarium of the Pacific).
-
Little fish hide in the lion's mane tentacles to stay safe.
Young walleye pollock dart in among a lion's mane's tentacles when danger comes.
Juvenile walleye pollock shelter among the tentacles, and butterfish ride the jelly while nibbling its bell (Aquarium of the Pacific).
-
A swimming lion's mane can look like a star.
At the end of each swimming stroke, a lion's mane can look like an eight-pointed star.
The 8 pairs of lobes give the contracted bell the look of an 8-pointed star at the end of the power stroke (Walla Walla University).
-
Leatherback sea turtles eat lion's mane jellies.
Leatherback turtles eat lion's manes and brush off the stinging cells with their flippers between bites.
Leatherbacks tolerate the nematocysts except near their eyes; how they gain energy from such a watery prey is not known.
Words to know
- tentacle
- a long, thin, bendy body part used to catch food
- bell
- the soft, round top part of a jellyfish
- oral arms
- frilly arms under a jellyfish's bell that carry food to its mouth
- polyp
- a small, tube-shaped stage that stays stuck in one place
- ephyra
- a baby jellyfish that has just broken off a polyp
- nematocyst
- a tiny stinging capsule made by jellyfish and their relatives
Discovery challenge
-
Why is it called a lion's mane jellyfish?
Where does the lion's mane jellyfish get its name?
Which feature gives Cyanea capillata its common name?
- Its mass of long, hair-like tentacles
- It roars like a lion
- It lives in Africa
Show the answer
Its mass of long, hair-like tentacles
Its many long tentacles look like a lion's furry mane.
Its mass of long, thin, hair-like tentacles looks a bit like a lion's mane.
The mass of long, hair-like tentacles; capillata also comes from the Latin for hair.
-
Do lion's mane jellies live in cold seas or hot seas?
What kind of seas do lion's mane jellyfish live in?
Which describes the range of Cyanea capillata?
- Warm tropical seas
- Cold northern seas
- Freshwater lakes
Show the answer
Cold northern seas
They live in cold seas in the north.
They live in the Arctic and the cool northern Atlantic and Pacific Oceans.
Arctic and north boreal coastal waters, reaching Florida and Mexico in the Atlantic, mainly in winter.
-
What do lion's mane jellies like to eat?
Which of these is a favorite food of the lion's mane jellyfish?
Which prey does the Aquarium of the Pacific single out for Cyanea capillata?
- Seaweed
- Moon jellies
- Sand
Show the answer
Moon jellies
They like to eat other jellies, like moon jellies.
They eat small fish, copepods and other jellies, especially moon jellies.
Other jellies, especially moon jellies; large ones are digested on the oral arms.
-
What hangs on a polyp before the baby jellies swim away?
What does a lion's mane polyp grow before baby jellies break off?
What forms during strobilation in Cyanea capillata?
- A stack of tiny jellies, like plates
- A shell
- Feathers
Show the answer
A stack of tiny jellies, like plates
The polyp makes a stack of tiny jellies, like a pile of plates.
The polyp grows a stack of tiny jellies that break off one by one as ephyrae.
A stack of disks that detach one at a time as ephyrae, the most mature on top.
Places where you might see it
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For parents & teachers
What children will learn
- Describe the lion's mane jellyfish's bell, lobes and tentacles.
- Explain how it catches and eats prey, including other jellies.
- Describe the polyp and medusa stages of its life cycle.
- Know that jellyfish can sting, even when washed up, and should never be touched.
Recommended ages: 3 to 17 · About 12 minutes
Talk about it
- Why might the same kind of jellyfish grow bigger in colder seas? What would you need to find out?
- How do small fish benefit from living near a stinging jellyfish?
- What should you do if you see a jellyfish on the beach?
Try at home or in class
- Lay a 9-meter piece of string along a hallway or yard to see how long a large lion's mane's tentacles can be.
- Stack paper plates and lift them off one by one to show how a polyp releases baby jellies.
Key vocabulary: tentacle, bell, oral arms, polyp, ephyra, nematocyst
Where these facts come from
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Lion's mane jellyfish (Cyanea capillata) , MarLIN, The Marine Biological Association of the UK
- Cyanea capillata , Invertebrates of the Salish Sea, Walla Walla University (Rosario Beach Marine Laboratory)
- Lion's Mane Jelly , Aquarium of the Pacific
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 27, 2026. Spotted a mistake? Tell us.