The common jellyfish is carnivorous, and feeds mainly on a variety of planktonic species such as molluscs, crustaceans, young worms and copepods (3). The plankton is caught in a layer of mucus that covers the jellyfish. Tiny hair-like structures called 'cilia' on the body of the jellyfish produce currents by beating. These currents transport the captured plankton towards the edge of the 'bell', where it is removed with the arms and passed to the mouth (2). The tentacles around the margins of the bell and the arms bear stinging cells, which are occasionally used to catch small fishes and other prey (2). The sexes are separate and fertilisation occurs internally; the sperm is taken into the female's body via the mouth (2). The fertilised eggs undergo development in pockets in the arms that surround the mouth. The free-swimming larvae (known as 'planulae' larvae) are released during autumn; after some time these larvae settle and develop into tiny sessile animals ('scyphistomae'), which reproduce asexually and release free-swimming tiny immature jellyfish (called 'ephyrae'), which feed on plankton and become mature after around 3 months (2).