Irukandji jellyfish

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The Irukandji jellyfish (Carukia barnesi) is a small, extremely venomous box jellyfish of the class Cubozoa that occurs in the waters of north Queensland, Australia. A mature Irukandji jellyfish's bell is only 12 mm in diameter and its depth no more than 25 mm. It has four contractible tentacles ranging in length from 5 cm to 1 m.

Its sting precedes painful symptoms known as "Irukandji syndrome", named so by Hugo Flecker in 1952 after an aboriginal tribe of Cairns. The jellyfish itself was identified only in 1964 by Dr. Jack Barnes; in order to prove it was indeed the cause of Irukandji syndrome, he captured the tiny jelly and stung both himself and his son. It takes part of its scientific name from Barnes.

Unlike other jellyfish, the Irukandji jellyfish has stingers (nematocysts) not only on its tentacles (which are arranged in clusters that look similar to drops of water), but also on its bell. Also unique to this jellyfish is that the venom is injected only from the tip of the stinger (cnidocyst) rather than the entire length. This explains why the initial sting is mild and the delayed reaction to the venom as the venom often has to travel farther to a vein to be distributed throughout the body.

So far, very little is known about the life and toxin of the Irukandji jellyfish, partly because it is very small and fragile. But the above mentioned researchers believe the reason for the potent venom is because Carukia barnesi feeds on tiny fast moving fish. As the jellyfish is extremely small to begin with the stunned fish must be stopped immediately if Carukia barnesi is going to feed on it. Judging from statistics, it has been conjectured that the Irukandji syndrome may be produced by several species of jellyfish, however only Carukia barnesi is proven to cause the Irukandji syndrome.

Vinegar has been found to deactivate Irukandji jellyfish stingers.

Irukandji syndrome is produced by a very small amount of venom and includes severe pains at various parts of the body (typically excruciating muscle cramps in the arms and legs, severe pain in the back and kidneys, and a burning sensation of the skin and face), headaches, nausea, restlessness, sweating, vomiting, high heart rate and blood pressure. As of 2006, no antivenom is known. The sting itself is only moderately irritating, the severe syndrome being delayed for 5-120 minutes (30 minutes on average). The severity of pain is apparent in a Discovery Channel show on Carukia barnesi when two researchers (Jamie Seymore and Teresa Carrette) are stung. Even under the "maximum dose of morphine", Teresa remarked that she "wished she could rip her skin off", and is later seen writhing uncontrollably from the pain, while lying on her hospital bed. Jamie said he wished that he was stung by Chironex fleckeri instead since "the pain goes away in 20 minutes or you die". The pain from Carukia barnesi can last 2 weeks. Another recent program that aired on the Discovery Channel entitled "Stings, Fangs and Spines" featured a 20 minute spot on Irukandji Syndrome. In the segment, a young Australian woman was stung and developed a severe case of Irukandji syndrome. In a testament to the severity of pain involved, a re-enactment (featuring the actual victim portraying herself) shows her screaming and violently thrashing around on the hospital bed in an almost convulsive state, for the bulk of the segment. She later commented that this unbearable pain lasted for hours, and "I didn't think it was possible for anyone to endure that level of pain without turning into a vegetable". When properly treated a single sting is normally not fatal, however, two people in Australia were believed to have died from Irukandji stings, greatly increasing public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes.

References

Flecker H. Irukandji sting to North Queensland bathers without production of weals but severe general symptoms. Med J Aust 1952; 2: 89-91.
Barnes J. H. Cause and effect in Irukandji stingings. Med J Aust 1964; 1: 897-904.
S. H. Anesmum RSP Adl. 2006.

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