Visitors to the Sea Life London Aquarium can view a special display in time for World Jellyfish Day.

In a UK first, experts at the aquarium have raised Barrel jellyfish, having bred the species from their juvenile stage as polyps in its specialist breeding laboratory.

The mushroom-shaped creatures are the UK’s largest jellyfish, growing up to one metre wide in the wild.

Barrel jellyfish are the UK’s largest jellyfish (Yui Mok/PA)
Barrel jellyfish are the UK’s largest jellyfish (Yui Mok/PA)

Their bulky, frilly appearance comes from their having eight thick “arms”, each featuring tiny tentacles.

It is the first time the species – which are harmless and usually only seen as adults in UK waters in the spring and summer – will go on display at the aquarium.

Other varieties on display include moon jellyfish (Yui Mok/PA)
Other varieties on display include moon jellyfish (Yui Mok/PA)

Jack Willans, senior aquarist and lead jellyologist at Sea Life London Aquarium, said: “It’s pretty special to be the only aquarium in the UK to have reared Barrel jellyfish and put them on display.

“It’s the perfect way to celebrate World Jellyfish Day.

“It’s not been an easy feat to raise the Barrels as we’ve needed to ensure the water and feed remain consistent to allow them to grow, however I’m proud to say here at Sea Life London Aquarium we’ve managed to do just that.

“Barrel jellyfish can grow up to 50cms in diameter, so watch this space to see how big ours get.”

World Jellyfish Day is on Thursday.

The Barrel jellyfish will be on display alongside other varieties including Moon jellyfish, Rocket jellyfish, Upside-down jellyfish and Marble jellyfish.