The Wildlife Trust's North Sea Wildlife Project

Lion’s Mane Jellyfish - Cyanea capillata

(Photo credit Tony Howells)

What is it? A large jellyfish with a saucer shaped bell (usually red-brown in colour), frilled oral arms and long pale tentacles. Although a stinging jellyfish, small fish can often be found sheltering  around them.

How big is it? This is the largest known species of jellyfish.  The largest individual ever recorded washed up on a beach in Massachusetts Bay in 1870. It had a bell 2.3m in diameter and tentacles of 36.5m, longer than a fully grown blue whale!  In Britain, the lion’s mane jellyfish rarely reaches 50cm across, with tentacles up to 5m long.

What does it eat?  The lion’s mane jellyfish is a filter feeder, using its long tentacles to capture prey from the surrounding water. This includes plankton,  fish and other jellyfish. Prey is then passed to the mouthparts to be digested.  

Where do they live?  This species prefers cold water, and are found mainly in northern areas.  The larger individuals usually live in the colder regions.  These are free floating animals, usually found in the top 25m of water.  They are largely dependant on currents for transportation, but can also  pulse their bell rhythmically to move around.

How can I find them?  You can often see Lions Mane jellyfish in the summer from small boats off the North Sea coast.  These jellyfish also get washed up on beaches, but be careful and they have a severe sting.