Creature Feature by Dr Gerald Goeden: May 2014

Box jellyfish have cube shaped bodies and are considered to be more complex than other jellyfish. Because they have such powerful stings box jellyfish are called sea wasps. The best-known species of box jellyfish is Chironex fleckeri. It is part of a dangerous group of about 19 different species.

Box jellies live in

Australia

, the

Philippines

, Hawaii,

Vietnam

, and many other tropical seas. Box jellyfish are extremely venomous and have killed many people. The Chironex fleckeri and the Carukia barnesi (called Irukandji) have the most powerful venom of any animal in the world.

Stings from such species are extremely painful and are often fatal. Box jellyfish stings are believed to have caused more than 5,500 deaths (Wikipedia). A severe sting can kill in as little as 3-4 minutes. Sometimes a person who gets stung will have a heart attack or drown before they can return to the shore or boat.

The tiny Irukandji is thumb-nail size.

Scientists have calculated that the amount of venom in one animal is enough to kill 60 adult humans. Most of the box jellyfish sting comes from tiny cells on its trailing tentacles. There are about 500,000 stinging cells (called nematocysts) on each tentacle. Each stinging cell is equipped with a microscopic harpoon that shoots out and injects a tiny amount of venom. The venom has several effects attacking the victim’s nervous system, heart, and skin.

The stinging cells are activated by touching another living animal. When scuba diving with box jellyfish, Reef Ninja Scientists wear special thin ‘lycra’ dive suits that don’t trigger the stings. Wearing gloves and a hood protects the rest of our bodies.

The biggest box jellyfish is Chironex fleckeri. It grows to the size of a small melon and it is this species that has caused most of the deaths. Surprisingly, the thumbnail-sized Irukandji is the next most dangerous being responsible for serious stings requiring hospitalization and even several deaths. Many cases of drowning are thought to be caused by the intense pain of Irukandji stings.