1. Are they dangerous?

With tentacles three metres long and covered with stinging cells, it’s better not to get too close to the Lion’s Mane jellyfish.  They have a very severe sting that can produce blisters, irritation and muscular cramp and may even affect respiratory and heart function. The tentacles are arranged in eight bunches, with each bunch containing over 100 tentacles. The oldest tentacles are often coloured dark red. Fragments of tentacles, left on buoy ropes for example, retain their stinging power.

Lion’s Mane Jellyfish, Cyanea capillata. Photo: Tim Nicholson

2. How to treat a Lion’s Mane Sting?

  1. Rinse with vinegar
  2. Place hot pack on affected area for 40 minutes, or place into hot water (45 oC).
Lion's mane jellyfishImage: Tim Nicholson
Photo: Tim Nicholson

3. How Big are they?

Its body can be 2 metres across, making it one of the largest species of jellyfish. Add in the tentacles, and the largest recorded stretched a massive 36.5 m. Starting out life in late winter as a small member of the plankton, not more than a few centimetres across, in just a few months the Lion’s Mane achieves its monstrous size.

Lion's Mane Jellyfish by Tim NicholsonImage: Tim Nicholson
Photo: Tim Nicholson

4. What do Lion’s Mane Jellyfish eat?

The jellyfish are predators. They eat zooplankton, small fish and moon jellyfish.

Photo: PublicDomainPictures/Pixabay

5. How Long do they Live?

Just one year.

6. Where will I see a Lion’s Mane Jellyfish?

Look out for the Lion’s Mane in the North and Irish Seas, the Arctic and Pacific Oceans, and around the coast of Australia. They are mostly no deeper than around 20 metres.

References and Further Reading

Lion’s Mane Jellyfish: Big and Dangerous
Great British Marine Animals, by Paul Naylor
The Marine Life Information Network
Doyle, T.K.; Headlam, J.L.; Wilcox, C.L.; MacLoughlin, E.; Yanagihara, A.A. Evaluation of Cyanea capillata Sting Management Protocols Using Ex Vivo and In Vitro Envenomation Models. Toxins 2017, 9, 215. https://doi.org/10.3390/toxins9070215

Image credits:

  • Lion’s mane jellyfish: Tim Nicholson
  • Lion’s Mane Jellyfish: Tim Nicholson

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