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Jellyfish Gone Wild — Text-only | Flash Special Report
Australia

THE EXPANDING RANGE OF POTENTIALLY DEADLY BOX JELLYFISH

They say that “everything in Australia either bites or stings.” But Australia’s reputation as an epicenter of freak animal assaults is currently being promoted particularly aggressively by various species of box jellyfish whose ultra-venomous stings cause Irukandji syndrome.

Irukandji syndrome includes a range of agonizing symptoms, including racking body pain, vomiting, skyrocketing blood pressure, high heart rate and sometimes even heart failure. On a 1-to-10 pain scale, Irukandji syndrome rates a “40,” says Jamie Seymour of James Cook University in Australia, who was stung by Irukandji jellyfish during a research dive.

Since about 2002, Australia has experienced “unprecedented occurrences of Irukandji jellyfish,” says Seymour. The result: hundreds of hospitalizations as well as two confirmed deaths.

Six species of box jellyfish are known to cause Irukandji syndrome. Nevertheless, 10 or more jellyfish species are suspected of causing the syndrome, and Irukandji deaths are probably underestimated because the syndrome is difficult to diagnose.

VEXING ENVENIMATORS
Irukandji syndrome presents particularly vexing problems because:

  • Irukandji jellyfish are among the world’s most venomous creatures.
  • Some species of Irukandji jellyfish are tiny and transparent and therefore virtually invisible in the water.  These small species are even small enough to slip through nets used to protect beach-goers from a larger and deadlier species of box jellyfish species called Chironex fleckeri, which is the most venomous animal on Earth.
  • Irukandji jellyfish are unpredictable.  These jellyfish can strike in any of the coastal beaches, reefs and islands throughout the northern half of Australia, including the Great Barrier Reef.  And, while their stings are most common during the Australian summer, they have occurred during every month of the year. 
  • Reports of Irukandji syndrome are increasing. This is probably happening for two reasons:
    1. Diagnosis and reporting of Irukandji syndrome increased after the two Irukandji deaths in 2002.
    2. The absolute numbers of Irukandji stings may be increasing.  Why?  Probably because water temperatures are rising, says Seymour.  This warming expands the range of Irukandji’s jellyfish into southern waters that used to be too cold for them. It also extends the summer season within Irukandji habitat; a longer summer means a longer Irukandji season. 

BIG BOX JELLYFISH AND RISING TEMPERATURES
Chironex fleckeri only live in calm waters that are stilled by offshore reef systems. Therefore, no matter how high water temperatures get, these deadly creatures are unlikely to colonize areas without reef systems, says Seymour.

Nevertheless, Chironex fleckeri currently kill an average of one person and dozens of other people throughout the world’s tropical waters annually. But because many indigenous people throughout the range of box jellyfish lack access to medical care and because their deaths are not recorded in death certificates, Seymour suspects that worldwide counts of box jellyfish stings may be seriously underestimated. His suspicions are supported by a recent informal survey indicating that most indigenous families in Thailand know of at least one family that has lost a family member to box jellyfish.

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Caption/Credit:

CHIRONEX FLECKERI, THE WORLD’S
MOST VENOMOUS ANIMAL
Chironex means “the hand of death” in Latin and Fleckeri honors Hugo Fleckeri, a jellyfish researcher. Credit: Courtesy of the Great Barrier Reef Marine Park Authority for and on behalf of the Commonwealth of Australia

STEALTHY STINGER
The tiny Carukia barnesi jellyfish causes Irukandji syndrome, a torturous, potentially deadly syndrome. Its transparent, peanut-sized body and threadlike tentacles, which may extend several feet, are virtually invisible in water.
Credit: Dr Jamie Seymour, James Cook University