Moon jellyfish

How it lives

Moon jellyfish have a clear, saucer-shaped bell with four horseshoe-shaped rings in the middle, often violet, pink or yellowish, and a fringe of short tentacles with stinging cells. What was once called one species, Aurelia aurita, is really a group of about 28 lookalike Aurelia species around the world. Aurelia aurita itself belongs mainly to the cool North Atlantic, where it is the most common jellyfish in Britain and Ireland, including estuaries, harbours and sea lochs. Other Aurelia species live elsewhere, including Palau's marine lakes.

Where it goes

Not a migrant. It pulses gently and drifts with the water. Its larvae settle on hard surfaces and grow into tiny polyps, which bud off baby jellies. These usually become adults in about 3 months, and some take up to about 2 years.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

Numbers change a lot: huge local swarms in some years and none in others, sometimes so dense they slow small boats. Jellyfish blooms often match warm water and fewer small fish, and human changes to coasts may help jellies, but direct proof is still limited.