- Scientific name: Aurelia aurita
- Also known as: Moon Jellyfish
- Size: Usually around 20cm across but can be double this size.
- Distribution: Found throughout all of the temperate and tropical seas of the world.
The common jellyfish is widespread throughout all of Britain and Ireland’s coastline, especially in the summer months. The umbrella is usually translucent, while the internal organs often have an orange, red or violet tinge to them. The tentacles contain stinging cells which can inflict mild pain (often compared to a nettle sting) if they come into contact with humans. Like all jellyfish, the common jellyfish are very poor swimmers which can only propel themselves weakly by contracting and extending their body. Even a feeble tidal flow will overpower the common jellyfish and it will have no choice other than to be pushed wherever the tide will take it.
Common jellyfish feed mainly on plankton and very small aquatic crustaceans which are caught in the tentacles and then manoeuvred to the mouth where they are digested whole. Common jellyfish can be found very close to the shore, often in estuaries and harbours, and can withstand water with a very low salinity content. A storm or period of bad weather can see masses of common jellyfish washed up onto the shore in large numbers.