Barrel Jellyfish

During the warm summer of 2014, our coasts are being invaded by swarms of alien-looking creatures the size of dustbin lids! Where are they coming from? Why are they here? And are they as frightening as they seem?

Fast Facts

Latin name: Rhizostoma pulmo

Notable feature: Large jellyfish with eight thick arms

Rarity in the UK: Rare / Common

Where in the UK: Atlantic Ocean, off the South and West Coast

Jellyfish are some of the most ancient and simple animals on the planet. These bizarre creatures have drifted through our oceans for over 500 million years, despite lacking a brain, heart or blood. Their soft bodies are over 90% water, and move in a mesmerising pulsing motion operated by a simple net of nerves. Though infamous for their stinging tentacles, most species are harmless to humans.

Sea monsters or gentle giants?

Several jellyfish visit UK waters. The Barrel jellyfish is our largest, with a diameter of up to 90cm and weights of up to 35 kilos. In summer and autumn they may swarm off the coast, sometimes washing up in large numbers.

These giant jellyfish swarms cause quite a stir. However they are gentle giants. Barrel jellyfish feed entirely on tiny plankton, so their sting is too weak to hurt humans.