Lion’s Mane Jellyfish

Lion's Mane Jellyfish

  • Scientific name: Cyanea capillata
  • Size: Usually up to 70cm across but can grow to over 2 metres across and have tentacles 40 metres long.
  • Distribution: Generally found in cold and temperate waters. Found in northern European waters but absent from the Mediterranean and any further south.

The lion’s mane jellyfish is a rare sight in the United Kingdom and Ireland, although it has turned up on a sporadic basis almost everywhere, from locations as diverse as the Shetland Islands, north east England and south west England and Wales. Its most common distribution around the UK is in the English Channel and off the coast of Cornwall.

This species is usually around 50cm across when found in British waters, but, as the largest jellyfish species in the world it can grow to two metres (6ft) across, and have tentacles over 40 metres (130ft ft) in length, making it one of the longest animals in the world. It is usually an orange, red or yellow in colour, with a shallow umbrella. It has a number of thick tentacles as well as very long, thin tentacles which trail behind it as it moves through the water. These tentacles are used to catch all manner of sea creatures which the lion’s mane jellyfish comes across, with prawns, shrimps smaller jellyfish and pelagic crustaceans making up the majority of its diet, although small fish are also taken. Lion’s mane jellyfish may themselves become prey for sunfish and sea turtles. Thsi species has a lifespan of around one year.

Lion's Mane Smithsonian

A life size model of a lion’s mane jellyfish (alongside a thresher shark) at the Smithsonian Museum of Natural History in Washington D.C., USA.

The lion’s mane jellyfish has a very powerful sting which can cause serious harm to any humans it comes into contact with. Being stung by a lion’s mane jellyfish can cause blistered red skin and intense pain. Most healthy people will simply have to wait for the pain to pass. However, in rare cases further complications such as muscle contractions and cramps, respiratory problems and even heart attacks can be caused by the lion’s mane jellyfish’s sting. Anyone finding a lion’s mane jellyfish washed up on the beach should also be aware that the tentacles of this species retain their potent sting long after the jellyfish has died, and dead specimens should therefore never be touched under any circumstances. Certain wind and tide conditions can see groups of lion’s main jellyfish cluster together in British waters, as seen off the coast of Cornwall in 2010. In 2010 around 150 people were stung by a single lion’s mane jellyfish which had already died off the coast of New Hampshire in the USA. The jellyfish was able to sting so many people as its tentacles broke up and floated through the water after officials tried to lift the dead jellyfish onto a boat. Five people were taken to hospital but no one was seriously injured.

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