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irukandji - psychological warefare of jellyfish

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The Irukandji

The Irukandji are tiny, highly poisonous jellyfish around 1 cubic centimeter in size. That's about the size of your fingertip. So... they can slip through protective nets and sting unaware victims. The Irukandji were thought to be mostly found around Australia, but now researchers are discovering them in many areas, such as Hawaii and Japan and migrating climate patterns are allowing even further movement of these jellyfish. While most jellyfish have stingers on their tentacles, Irukandji also have stingers on their bell piece as well as the ability to fire stingers from the tip of their tentacles.

The scientific name for these jellyfish, Carukia barnesi, is named after Jack Barnes, the man who linked the Irukandji to certain reoccuring symptoms in the early 1960s.

Irukandji painting by Beth Josey, 2011

Unfortunately, very little research is available for them as they are very fragile. Keith Tiong for the Oxford Journals presents a much needed research on the subject.

A 26-year-old man was admitted to a local hospital in Far North Queensland, 2 hours following a sting on his body trunk from a jellyfish similar in description to the Irukandji. The subject remembers contact, while diving, with a small transparent jelly fish, similar in size and character to Carukia barnesi. This occurs near the waters of Cooktown, a seaside resort in Far North Queensland in December, during summer, a peak period for Carukia barnesi.

On admission to hospital, the subject developed symptoms consistent with ‘Irukandji syndrome’ which included pain, a burning sensation of the skin and face, restlessness, nausea, abdominal cramps, sweating, hypertension (high blood pressure), tachycardia (heart rate over 100) and a “feeling of impending doom”. The Irukandji jellyfish sting also causes the sympathetic nervous system to go into overdrive. If we remember, the sympathetic nervous system is responsible for excited body responses. The case study subject's physical examination was consistent with an excited body state, with a sudden release of catecholamines (dopamine, epinephrine, norepinephrine) which caused an excess of those chemicals and persistent high heart rate and high blood pressure. One of the symptoms of excess dopamine is involuntary tremors, and some symptoms of excess norepinephrine are mania, arousal, agitation, and anxiety.

His chest X-ray and cardiovascular examination at this stage were consistent with a mild degree of transient pulmonary edema (fluid in the lungs), related to failure of the left ventricle (part of the heart). His blood count also indicated some Thrombocytopenia (blood has a lower than normal number platelets, which are involved in clotting the blood).

The most interesting part is, with all these factors combined, as well as reports by victims (one being Barnes himself) researchers have found a curious result: apparently the Irukandji jellyfish triggers a psychological response making you think you're going to die.

There is no antidote for the venom, so someone who is stung just has to wait out the pain. In most cases, the Irukandji venom is not fatal, although there have been a few deaths.

Click here to read Keith Tiong's full study on the Oxford Journals website.

Click here to watch a 1-min video on how Irukandji jellyfish stingers work on YouTube.



Additional Reading*:

Gershwin, Lisa-Ann. "Malo kingi: A new species of Irukandji jellyfish (Cnidaria: Cubozoa: Carybdeida), possibly lethal to humans, from Queensland, Australia." Zootaxa, 1659 (2007): 55-68.

Bentlage, Bastian, Paulyn Cartwright, Angel A. Yanagihara, Cheryl Lewis, Gemma S. Richards, and Allen G. Collins. "Evolution of Box Jellyfish (Cnidaria: Cubozoa), a Group of Highly Toxic Invertebrates." Proceedings of the Royal Society B: Biological Science227.1680 (2010): 493-501 [full pdf download]

"Jack Barnes and the Irukandji Enigma" by Chris Nickson for


*None of the content in "Additional Reading" resources is related to, nor do we confirm the authenticity or views expressed therein.