Common jellyfish

Jellyfish & Ctenaria

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Identity card

common jellyfish

Scientific name:: Aurelia aurita

Family:: Ulmaridae

Class:: Scyphozoa

Phylum:: Cnidaria

Year of description:: Linnaeus, 1758

IUCN Status:: Not Evaluated

Distribution:: This jellyfish is widely found in all oceans, except in the very cold waters of the North and South Poles.

Habitat:: The common jellyfish is found in all oceans and often lives on the surface of the water.

Size:: When fully extended, its umbrella measures 40 cm in diameter.

Diet:: Its diet mainly comprises herring larvae and small crustaceans. It can also eat other jellyfish and even its own larvae.

At Nausicaá, the first baby moon jellyfish were born in 1995.

The lifecycle of a jellyfish has two phases. The first is the fixed phase when the polyp attaches itself to a stone on the seabed. The second, free phase starts when the season changes. The polyp detaches itself from its stone and turns into a mini jellyfish that will then grow into an adult. Following fertilisation between two adult jellyfish, a new larva will be deposited on the seabed and the cycle starts again!

did you know?

Where is the animal to be found?

This jellyfish lives in all oceans. The common jellyfish often moves about on the surface of the water, carried by the currents out at sea or in coastal waters. It is therefore sometimes to be seen in ports. Summer temperatures favour the development of the larvae.

How can it be recognised?

This jellyfish is a translucent bluish-white colour. At the centre of the umbrella, there is a shape like a four-leaf clover: in males it is a violet colour and in females it is whitish. Its flared umbrella reaches 40 cm in diameter.

What is distinctive about it?

It has a digestive system between its tentacles, light-sensitive organs, muscles and nerves. It also has stinging cells that deliver poison.
Jellyfish are a type of plankton. Though they usually drift, carried by the currents, they also have a sort of propulsion by reaction.
They swim by contracting the umbrella to expel water. Their muscles then relax and the umbrella opens again. Moon jellyfish float and swim but cannot resist sea currents.
In order to grow and reproduce, a jellyfish must consume several times its weight in food each day.
Jellyfish are cnidarians like anemones and coral. They are made up of 95% water.