RHIZOSTOMA OCTOPUS – The Barrel Jellyfish

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This year we have been seeing an amazing number of Barrel jellyfish on our dives and snorkels here in the Kinsale area. Rhizostoma octopus is a surprisingly solid jellyfish, which can grow up to one meter in diameter. Its Bell is dome shaped and is a very pale dirty yellow colour with purple lobes around the edge. This jellyfish has eight oral arms that look a bit like a cauliflower but has no tentacles. The Ecojel project have measured a barrel jellyfish that was 80cm in diameter and weighed 35kg.

https://www.youtube.com/watch?v=cxtocrPwRpw

Barrels are sometimes referred to as the “basking sharks” of the jellyfish worlds, because although they are quite large they feed only on plankton. Beneath it’s bell the barrel have hundreds of tiny mouths (the Pores) which lead to a highly branched digestive system. Each mouth is surrounded by tiny stinging tentacles. Their sting is not powerful enough to harm humans, but only the plankton small enough to enter their tiny mouths. The Barrels are constantly swimming up and down in the water column feeding on the plankton. They have sensory cells that enable them to orientate and tell up from down

A lot of small juvenile fish seek protection between the eight arms of the barrel jellyfish. however the Barrel itself is one of the favourite foods of the critically endangered leatherback turtle and these fantastic reptiles are seasonal visitors to our waters. So Keep your eyes peeled there is the potential to spot a leatherback turtle, fingers crossed!

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