Irukandji jellyfish (// IRR-ə-KAN-jee) are small and extremely venomous box jellyfish that inhabit marine waters of Australia and which are able to fire their stingers into their victim, causing symptoms collectively known as Irukandji syndrome. Their size is roughly a cubic centimetre (1 cm3). There are five known species of Irukandji: Carukia barnesi, Malo kingi and the recently discovered Malo maximus, Malo filipina and Malo bella.
The symptoms of Irukandji syndrome were first documented by Hugo Flecker in 1952. They were named after the Irukandji people whose country stretches along the coastal strip north of Cairns, Queensland. The first of these jellyfish, Carukia barnesi, was identified in 1964 by Jack Barnes; in order to prove it was the cause of Irukandji syndrome, he captured the tiny jelly and allowed it to sting him while his son and a lifeguard observed the effects.
Irukandji jellyfish were at one time thought to be in the northern waters of Australia only. Since then, according to a National Geographic documentary on jellyfish, the species has been found in waters as far north as the British Isles, Japan, and the Florida coast of the United States. There have been sighting and recorded injuries in the waters of Malaysia.
Irukandji jellyfish are very small with a bell about 5 millimetres (0.20 in) to 25 millimetres (0.98 in) wide (or wider) and four long tentacles, which range in length from just a few centimeters up to 1 metre (3.3 ft) in length. The stingers (nematocysts) are in clumps, appearing as rings of small red dots around the bell and along the tentacles.
Very little is known about the life cycle and venom of Irukandji jellyfish. This is partly because they are too small and fragile requiring special handling and containment. Its venom is very powerful. Researchers conjecture that its venom possesses such potency to enable it to quickly stun its prey, which consists of small and fast fish. Judging from statistics, it is believed that the Irukandji syndrome may be produced by several species of jellyfish, but only Carukia barnesi and Malo kingi have so far been proven to cause the condition.
Most jellyfish have stingers only on their tentacles but the Irukandji also has stingers on its bell. Biologists have yet to discover the purpose of this unique characteristic. The hypothesis is that the feature enables the jellyfish to be more likely to catch its prey of small fish.
Irukandji jellyfish differ from other box jellyfish species in that they have the ability to fire stingers from the tips and inject venom. Currently, it is not known whether this is for some special purpose.
Irukandji syndrome is produced by a small amount of venom and induces 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, an increase in heart rate and blood pressure, and psychological phenomena such as the feeling of impending doom. The syndrome is in part caused by release of catecholamines. The venom contains a sodium channel modulator.
The sting is moderately irritating; the severe syndrome is delayed for 5–120 minutes (30 minutes on average). The symptoms last from hours to weeks, and victims usually require hospitalisation. As with other box jellyfish, vinegar will deactivate unfired nematocysts on the skin but has no effect on the venom already in the body. Treatment is symptomatic, with antihistamines and anti-hypertensive drugs used to control inflammation and hypertension; intravenous opiates, such as morphine and fentanyl, are used to control the pain. Magnesium sulfate has been used to reduce pain and hypertension in Irukandji syndrome, although it has had no effect in other cases.
Irukandji are usually found near the coast, attracted by the warmer water, but blooms have been seen as far as five kilometres offshore. When properly treated, a single sting is normally not fatal, but two people in Australia are believed to have died from Irukandji stings in 2002, greatly increasing public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes. It is also unknown which jellyfish species can cause Irukandji syndrome apart from Carukia barnesi and Malo kingi.
- Gershwin, Lisa-Ann (2007). "Malo kingi: A new species of Irukandji jellyfish (Cnidaria: Cubozoa: Carybdeida), possibly lethal to humans, from Queensland, Australia". Zootaxa (1659): 55–68. Retrieved 2010-07-23.
- Li, R. (2011). "The pharmacology of Malo maxima jellyfish venom extract in isolated cardiovascular tissues: A probable cause of the Irukandji syndrome in Western Australia". Tox Letters 201 (201(3)): 221–9. doi:10.1016/j.toxlet.2011.01.003. PMID 21237252.
- Pearn, J. H. (1990). Australian Dictionary of Biography, Volume 14. Melbourne University Press. pp. 182–184. ISBN 0-522-84717-X. Retrieved 2013-10-01.
- Flecker, Hugo (1952-07-19). "Irukandji sting to North Queensland bathers without production of weals but with severe general symptoms". The Medical Journal of Australia 2 (3): 89–91. ISSN 0025-729X. PMID 14956317.
- Barnes, J. (1964). "Cause and effect in Irukandji stingings". Med J Aust 1: 897–904. PMID 14172390.
- "The pharmacology of Malo maxima jellyfish venom extract in isolated cardiovascular tissues: A probable cause of the Irukandji syndrome in Western Australia.". Toxicol Lett 201 (3): 221–9. Mar 2011. doi:10.1016/j.toxlet.2011.01.003. PMID 21237252.
- National Geographic. Jellyfish Invasion. Retrieved 2013-10-02.
- James D Grady, MD (December 2003). "Irukandji-like syndrome in South Florida divers". Annals of Emergency Medicine 42 (6): 763–766. doi:10.1016/S0196-0644(03)00513-4. PMID 14634600. Retrieved 2013-10-02.
- Tibballs, J. (December 2006). "Australian venomous jellyfish, envenomation syndromes, toxins and therapy". Toxicon 48 (7): 830–59. doi:10.1016/j.toxicon.2006.07.020. PMID 16928389.
- Barnes, J. H. (1964-06-13). "Cause And Effect In Irukandji Stingings". The Medical Journal of Australia 1: 897–904. ISSN 0025-729X. PMID 14172390.
- Killer Jellyfish, Oasis
- Carrette, Teresa; Seymour, Jamie. "Jellyfish responsible for causing Irukandji syndrome" (PDF). James Cook University. Retrieved 2011-10-02.
- Greenland, P.; Hutchinson, D.; Park, T. (March 2006). "Irukandji Syndrome: what nurses need to know". Nursing and Health Sciences 8 (1): 66–70. doi:10.1111/j.1442-2018.2006.00255.x. PMID 16451431.
- Corkeron, M.; Pereira, P.; Makrocanis, C. (October 2004). "Early experience with magnesium administration in Irukandji syndrome". Anaesthesia and Intensive Care 32 (5): 666–9. PMID 15535491.
- Little, M. (August 2005). "Failure of magnesium in treatment of Irukandji syndrome". Anaesthesia and Intensive Care 33 (4): 541–2. PMID 16119507.
- Fenner, Peter J.; Hacock, John C. (2002-10-07). "Fatal envenomation by jellyfish causing Irukandji syndrome". The Medical Journal of Australia 177 (7): 362–3. ISSN 0025-729X. PMID 12358578.
- "Hope for lethal jellyfish cure". BBC News. 2003-01-31. Retrieved 2010-05-05.
- Lewis, Wendy (2007). See Australia and Die. New Holland Publishers. ISBN 978-1-74110-583-4. Retrieved 2013-10-02.
- Seymour, Jamie; Carrette, Teresa. "Identification of cubozoans responsible for causing Irukandji syndrome". James Cook University. Retrieved 2011-10-02.