Looking like some alien monster with big googly eyes, this huge jellyfish was one of many that get washed ashore and stranded on Gower beaches. There are often dozens on the shore of Rhossili Bay in various stages of decomposition. This particular fine and fresh specimen was seen on the rocks at Whiteford Sands. The Latin name is Rhizostoma octopus (Linnaeus). Common names for it include Barrel-mouthed or Dustbin-lid Jellyfish. It has a large, fairly firm umbrella shaped dome about 90 cm across; the overall length – stretched out with its tentacles extended – was well over a metre.
The wet gelatinous texture is repellent to some people but the colours of the various parts are attractive with shades of pink through a milky hue to shades of blue. A narrow, scalloped, purple fringe trims the lower edge of the umbrella. Viewing this animal from the underside, all the detailed anatomy is revealed. There is a pattern based on a fourfold or eightfold repetition. I think it is a splendid-looking creature.
Revision of a post first published 1 July 2009
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Jessica's Nature Blog 
That’s quite the jelly Jessica! Barrel Jellyfish and Root-mouthed Jellyfish are two common names I’ve come across while looking for images of them underwater. They certainly are magnificent creatures.
Could you explain why their scientific name includes the word ‘octopus’ instead of ‘jellyfish?’
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Thank you for the common names, AmyLynn.
I think the specific name ‘octopus’ comes from the Latin word for eight and there are eight arms hanging down from the underside of the dome. Most of the other jellyfish seem to have a pattern based on just four arms.
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That makes sense Jessica. Thanks for clarifying.
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I have seen many of these along Gower beaches, there is also a sky blue colour one sometimes found at Rhossili, I remember 2002 along the Pembroke coast as there were mass strandings of jellyfish, it was in the papers that year. i walked along Newquey beach an you would find a jelly every ten yards. These jellyfish are also know as Barrel jellys.
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Hi, Mike. Yes, there are often strandings of these jellyfish in a variety of colours along the Gower shoreline, aren’t there? Other species like Moon Jellyfish and Compass Jellyfish also seem to occur in large numbers from time to time.. When there are large numbers of Barrel Jellyfish, they attract migrating Leatherback Turtles which just love to eat them.
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