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Science & Nature • Marine Biology

Lion's Mane Jellyfish

The lion's mane jellyfish (*Cyanea capillata*) is one of the largest known species of jellyfish and is found in cold northern waters.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

The lion's mane jellyfish (Cyanea capillata) is one of the largest known species of jellyfish and is found in cold northern waters. It is named for its long, flowing tentacles, which can deliver a painful sting. The species is a marine cnidarian in the class Scyphozoa.

Taxonomy and naming

The lion's mane jellyfish is scientifically named Cyanea capillata and belongs to the class Scyphozoa within the phylum Cnidaria. Its common name refers to the long tentacles that resemble a lion's mane.

Description

This jellyfish is known for a large bell and very long trailing tentacles, which are arranged in eight distinct clusters. Reported size estimates vary, but it is consistently described as one of the largest jellyfish in the world.

Distribution and habitat

The species lives mainly in cold and temperate waters of the Northern Hemisphere, especially the Arctic, northern Atlantic, and northern Pacific. It is most often associated with open water, though some sources note occurrences in coastal waters and farther south.

Feeding and behaviour

Lion's mane jellyfish are carnivorous drift predators that feed on small fish, zooplankton, shrimp, and other jellyfish. They capture prey using stinging cells called nematocysts on their tentacles.

Human interactions

The species can deliver a painful sting, and some sources note that symptoms may include irritation, blisters, cramps, or effects on breathing in more serious cases. Human fatalities are reported as rare.

Key facts

  • It is considered the largest known jellyfish species.
  • Its range is primarily confined to cold waters of the Arctic, northern Atlantic, and northern Pacific Oceans.
  • The bell is typically translucent brown to reddish, with long tentacles arranged in eight clusters.
  • It is a predator that captures prey with stinging cells on its tentacles.
  • Its sting is usually painful and can sometimes affect more than just the skin.
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Canadian context

The species is relevant to Canadian readers because it occurs in cold northern Atlantic and northern Pacific waters, including marine areas near Canada.

Frequently asked questions

What is the lion's mane jellyfish?
It is a large marine jellyfish species, scientifically known as Cyanea capillata, and one of the biggest jellyfish known.
Where does it live?
It is found mainly in cold waters of the Arctic, northern Atlantic, and northern Pacific Oceans, with some populations reaching farther south.
How big can it get?
Sources describe it as one of the largest jellyfish, with bells up to about 1.8 m across and tentacles reported over 30 m long.
What does it eat?
It feeds on small fish, zooplankton, shrimp, and other jellyfish.
Is its sting dangerous to humans?
Its sting is usually painful and can cause irritation or more severe symptoms, but reported human fatalities are few.
Why is it called a lion's mane jellyfish?
The name refers to its long, flowing tentacles that resemble a lion's mane.

References

  1. Wikipediahttps://en.wikipedia.org/wiki/Lion's_mane_jellyfish
    Supports: Scientific name, broad range, and claim that it is one of the largest known jellyfish species.
  2. Encyclopaedia Britannicahttps://www.britannica.com/animal/lions-mane-jellyfish
    Supports: Taxonomy, cold-water Northern Hemisphere distribution, and status as the largest known jellyfish.
  3. Oceanahttps://www.oceana.org/marine-life/lions-mane-jellyfish/
    Supports: Bell and tentacle size estimates, habitat, prey, stinging cells, and general behaviour.
  4. The Wildlife Trustshttps://www.wildlifetrusts.org/wildlife-explorer/marine/jellyfish/lions-mane-jellyfish
    Supports: Scientific name, appearance, prey, sting, and occurrence around UK coasts.
  5. Monterey Bay Aquariumhttps://www.montereybayaquarium.org/animals-the-ocean/animals-a-to-z/lions-mane-jelly
    Supports: Size, toxic sting, and rarity of human fatalities.
  6. Virginia Institute of Marine Sciencehttps://www.vims.edu/bayinfo/jellyfish/guide/lions_mane.php
    Supports: Scientific name, size, colour, tentacle arrangement, and sting description.