Almost every jellyfish needs a piece of the seabed. This one never touches it.
The usual life cycle runs through a polyp: the larva settles on hard bottom, becomes a small anemone-like animal, clones itself for years and buds off young medusae when conditions turn. It ties the whole species to a coastline. The mauve stinger skips that stage completely and develops from egg to medusa in open water, which is why it can hold enormous populations with no coast involved at all, and why a bloom can appear in the middle of nowhere with nothing on the seabed to have predicted it from.
The animal itself is small: a warty mushroom of a bell to 12 cm (5 in), mauve to pink, trailing eight thin tentacles and four frilled arms several times its own length. It is an open-water drifter that reaches the coast only when wind and current deliver it, and it arrives in numbers when it does.
The name means night light. Disturbed in the dark it produces a blue-green glow from its own tissue - one of the few jellyfish that does - so a swarm crossed by a fin or a boat wake lights up along the line of the disturbance.
The sting is why it makes the news. Stinging cells cover the bell as well as the tentacles, so contact anywhere burns; the pain is sharp, the welts last days, and torn-off fragments of tentacle sting exactly as well as attached ones.
- small mushroom-shaped bell, mauve to pink, covered in fine warts
- eight long thin tentacles and four frilled arms, all far longer than the bell
- stinging cells on the bell itself, not only on the tentacles
- glows blue-green when disturbed at night
- bell up to 12 cm across
