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What is the size of a man's thumbnail, lurks in the tropical waters of Northern Australia's Barrier Reef, is almost invisible, and can kill a human in a few days?

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Carukia Barnesi

More commonly known as the Irukandji jellyfish and related to the Box jellyfish, this tiny creature has a 2cm bell and 4 tentacles 50 to 500 mm in length. Their preferred habitat is the deeper waters of the reef. but are often swept inland by currents, making them a threat not only to divers and snorkelers but tourists as well. Irukandji's sting, while not felt immediately, brings extreme pain throughout the body and, if left untreated, can resulted in death. These jellyfish are tiny, see-through, almost invisible and can easily swim through safety nets put up to protects swimmers and tourists on the coast of Northern Australia.

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The Box Jellyfish has the most deadliest venom known in the animal kingdom (but the Irukandji may soon take this spot). It is responsible for at least 5,567 recorded human deaths since 1954. Most of these have been perpetrated by the larger Box Jelly species.

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Unlike other jellyfish, Irukandji's venom is injected only by the tips of the tentacles, which is why the sting is mild and typically unnoticed until the venom starts to take affect. Despite this, they have stingers (which look like drops of water) along the entire length of the tentacles and on the bell.

Irukandji Syndrome

Those stung by Irukandji start to feel pain about 30 minutes after the initial sting and can expect several days (although sometimes just a few hours) of hell: Excruciating muscle cramps in the arms and legs, severe pain in the back and kidneys, a burning sensation of the skin and face, headaches, nausea, restlessness, sweating, vomiting, high heart rate and blood pressure and, in the worst case, death. One tourist suffered a fatal brain hemorrhage after coming into contact with the tiny jellyfish.

There is no known antidote for the sting, but as of last year (2007), magnesium phosphate is being used to treat Irukandji Syndrome.

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The filming of "Fool's Gold" (starring Kate Hudson and Matthew McConaughey) was temporarily suspended due to an Irukandji scare. Dr. Jamie Seymour found five Irukandji in the water and issued the warning.

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When properly treated, a single sting is not normally fatal, but at least two deaths have resulted from Irukandji Syndrome, with possibly many more which have been wrongly attributed to other causes.

The name, Carukia Barnesi, was given because of the dedication of Dr, Jack Barnes who, in 1964, spent several hours lying in the water in a wetsuit near Cairns. When a thumbnail-sized jellyfish swam past his mask Dr. Barnes stung himself, his son, and a lifeguard to make sure the specimen he had caught was the one responsible for Irukandji Syndrome. (Personally, I think Dr. Barnes should have been arrested for assault and attempted murder and the Irukandji should have been named after his son and the lifeguard.)

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A warning posted October 2nd, 2008 by Irukandji expert Dr. Lisa-Anne Gershwin from the Australian Marine Stinger Advisory Service says there could be huge blooms of the potentially deadly jellyfish along the Queensland's coast this summer.

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The information which is presently known about the Irukandji jellyfish is due in the most part to the extensive field-work and research of Dr. Jamie Seymour. "From November through to May everybody's forced to swim inside nets on the coasts. That changes the entire way the beach is used here."

FIRST AID

Dr. Michael Corkeron, of Queensland's Townsville Hospital, has reported successful results with magnesium infusions to fight the jellyfish's lethal venum.  "The remarkable thing is that magnesium infusium is a long-established, very safe and inexpensive treatment," he says.

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The Irukandji Jellyfish Web site

The CRC Reef Research Centre's literature about Irukandji

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