Australian Box Jelly

• It does not drift with the current: it swims actively at more than a metre a second, avoids obstacles and seeks out its prey, behaviour unusual for a jellyfish.
• It has twenty-four eyes in four clusters, some of them with cornea, lens and retina, even though the animal has no centralised brain.
• First aid is to apply vinegar, which stops the stinging cells still on the skin from firing, and a specific antivenom has existed since 1970.
• It is the deadliest jellyfish in the world: it is blamed for at least 64 deaths in Australia between 1884 and 2021, and some sources put the figure at 77 over the last century.
• It can kill in minutes. Deaths normally occur between 5 and 20 minutes after the sting, from cardiac arrest; its venom causes extreme pain, dermonecrosis, hypotension and arrhythmias.
• And it is no passive drifting jellyfish: it swims actively at several km/h and pursues its prey.
• It has 24 eyes, grouped into four sensory structures, some with a lens and retina capable of forming images. It uses them to find its way and to dodge obstacles, something exceptional in an animal without a centralised brain.
• Its tentacles reach three metres and are covered in millions of nematocysts.
• First aid is vinegar, which deactivates the nematocysts that have not yet fired and stops the situation getting worse, but it neither relieves the pain nor neutralises venom already injected. An antivenom has existed since 1970, though its real effectiveness is still debated.
• The great majority of stings are not fatal and amount to painful weals.
• In 2016 abundant populations were discovered below 50 m depth on reefs off Western Australia, which broadened what was known of its ecology.

Skeleton type

Invertebrate - no rigid skeleton (cnidarian)

Habitat and environment

Shallow coastal waters and river mouths of northern Australia and the Indo-Pacific

Sources consulted: Wikipedia (es): Chironex fleckeri

Best time: Southern summer, October to May, in the coastal waters of northern Australia

The pins mark the parks and dive sites where its presence is documented.