Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by theircube-shaped medusae. Some species of box jellyfish produce extremely potentvenom: Chironex fleckeri, Carukia barnesi and Malo kingi. Stings from these and a few other species in the class are extremely painful and can be fatal to humans.
Box jellyfish has been called “the world’s most venomous creature”, only a few species in the class have been confirmed to be involved in human deaths, and some species pose no serious threat at all. For example, the sting of Chiropsella bart only results in short-lived itching and mild pain.
In Australia, fatalities are most often perpetrated by the largest species of this class of jellyfish,Chironex fleckeri. Angel Yanagihara of the University of Hawaii’s Department of Tropical Medicine found the venom causes cells to become porous enough to allow potassium leakage, causing hyperkalemia, which can lead to cardiovascular collapse and death as quickly as within 2 to 5 minutes. She postulated that a zinc compound may be developed as an antidote
The recently discovered and very similar Chironex yamaguchii may be equally dangerous, as it has been implicated in several deaths in Japan. It is unclear which of these species is the one usually involved in fatalities in the Malay Archipelago. In 1990, a 4-year-old child died after being stung by Chiropsalmus quadrumanus at Galveston Island in the Gulf of Mexico, and either this species or Chiropsoides buitendijki are considered the likely perpetrators of two deaths inWest Malaysia. At least two deaths in Australia have been attributed to the thumbnail-sized Irukandji jellyfish.Those who fall victim to these may suffer severe physical and psychological symptoms, known as Irukandji syndrome.Nevertheless, most victims do survive, and out of 62 people treated for Irukandji envenomation in Australia in 1996, almost half could be discharged home with few or no symptoms after 6 hours, and only two remained hospitalized approximately a day after they were stung.
Box jellyfish are known as the “suckerpunch” of the sea not only because their sting is rarely detected until the venom is injected, but also because they are almost transparent.
In northern Australia, the highest risk period for the box jellyfish is between October and May, but stings and specimens have been reported all months of the year. Similarly, the highest risk conditions are those with calm water and a light, onshore breeze; however, stings and specimens have been reported in all conditions.