Mauve Stinger

• Its scientific name means "night light", after its bioluminescence.
• It goes straight from planktonic larva to young medusa, with no fixed polyp stage.
• It can form large ocean swarms, especially in the Mediterranean.
• It is the jellyfish responsible for most of the ruined bathing days in the Mediterranean, and its sting is painful and leaves a mark for weeks.
• It has no polyp stage. Unlike almost all jellyfish, which alternate a fixed stage on the bottom with the swimming medusa, this one develops directly from egg to medusa in the open sea.
• And that explains its behaviour: since it does not depend on a substrate, its populations are entirely oceanic and reach the coast driven by wind and currents, in unpredictable waves.
• It is bioluminescent, hence its name: when disturbed it gives off bluish flashes, visible at night in the wake of ships.
• Its outbreaks in the Mediterranean have become more frequent, and are linked to warming waters, the overfishing of its predators and competitors, and changes in the currents.
• It eats zooplankton and fish eggs and larvae, which makes it a direct competitor of the very fish whose overfishing favours its spread.

Skeleton type

Invertebrate - no skeleton, gelatinous body (cnidarian)

Habitat and environment

Temperate and tropical oceanic waters worldwide, especially abundant in the Mediterranean

Birth weight

A microscopic planula larva that develops straight into an ephyra (the juvenile medusa stage), with no bottom-living polyp phase

Size at birth

A microscopic ephyra as it develops from the planula

Sexual maturity

It matures within its single annual life cycle

Gestation / incubation

No incubation; the fertilised egg develops straight into a planula and then an ephyra

Litter / clutch size

It breeds by releasing gametes into the water for external fertilisation; the sources consulted put no figure on the number of eggs

Sources consulted: Animal Diversity Web; Animalia.bio; Dimensions.com; Snorkel Things; Zooplankton Guide (Scripps Institution)