Let's Talk Science- Irukandji
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Let's Talk Science- Irukandji

As a marine biologist, I have always had a special place in my heart for organisms known as Cnidarians- better known as jellyfish.  The phylum Cnidaria also includes corals, anemones, and hydroids (like the Portugese Man-of War, which isn’t a true jellyfish).  The innate beauty of these animals, as well as their incredible evolutionary history, has caused me to foster a deep respect for them.  There are many different kinds of jelly out there, but one kind seems to stand alone- Irukandji.

Irukandji jellyfish have been getting more and more press in the past few years, though they remain relatively unknown to the public.  They are part of the class Cubazoa, commonly known as the box jellies.  Box jellies are known for their strong swimming ability, characteristic box shape, and dangerously potent venom.  Irukandji are no different. Their venom is known to cause an excruciating and sometimes deadly reaction known as Irukandji syndrome.  Before I get into all the lovely details of that, let’s talk a little bit about the critters themselves.

The term ‘Irukandji’ isn’t actually a classification of these animals- it is only used to describe the effects of the sting.  There are currently two described species of Irukandji jellyfish: Carukia barnesi and Malo kingi. When I say they are relatively new, I mean it. M. kingi was only described to science in 2007, and was named after a tourist who died from a sting.  These animals are characterized by their tiny size, tropical distribution, and incredibly dangerous venom- 100 times more potent than that of a Cobra.  For an idea of how small Irukandji are, look at your thumbnail.  That’s about the size of one.  This makes Irukandji the biological equivalent of a ninja with a tactical nuke- small, silent and almost invisible… but with one heck of a wallop.

Stings from Irukandji jellies are generally not incredibly painful at first.  However after several minutes, victims begin to succumb to the syndrome.  This causes excruciating pain, often of the back and kidneys, severe muscle cramps, and other symptoms.  These symptoms can last anywhere from hours to weeks, and seem to be worse in women.  The syndrome itself can be deadly.  Check out this pair of scientists who get stung in Australia-


-and that’s with a maximum dose of Morphine!  Towards the end of the video, the guy actually says that he would rather work with Chironex fleckeri, better known as the Sea wasp- the most lethal jellyfish in the world.

So, what do you do to avoid this little beast?  Well, the first step is not to go swimming in Australia in October- when the jellies start to appear.  But if you are in the USA, you are nice and safe, right?


Well, maybe.  Irukandji are native to Australian waters, so the only way they could appear in North American waters is if they were introduced and became an invasive species.  If that happened, there would be reports of victims being stung…

…which is exactly what is happening.  According to National Geographic, these jellies have been found off the coast of Florida in recent years.  If this is the case, they could gain a foothold and become an invasive species, like the pacific lionfish has off the U.S. East coast.  This would require favorable physical, chemical, and biological conditions.

Because so little research has been done on these animals, information about temperature tolerances, life history, and similar aspects are currently unknown.  If any parallels are to be drawn from other members of the family Cubazoa, they likely have a wide range of temperature tolerances and can undergo directional, powered swimming (something most jellyfish cannot do- they simply drift with the water, or in the case of the Portugese Man-of-war, with the wind).

National Geographic states that cases have been reported in Florida, but as there is no critical scientific literature that acknowledges this (to my knowledge at least), these reports remain conjecture.  It is known, though, that at least 3 military divers in Florida experienced symptoms similar to Irukandji syndrome; however, the species that caused it is unknown. According to the scientists that published the report, the culprit was likely a species of family Cubazoa.  Irukandji are two out of approximately 40 known species in this family.

How could Irukanji get here?  Many animals establish themselves in foreign environments by hitching rides on ships, or in products that travel from one place to another.  However, there is an issue with each of these theories.  Jellies live in a world without walls- they have no structure and no means by which to deal with contacting hard surfaces.  They can survive doing this once in awhile, but generally it is very detrimental to their well being- which is why keeping jellyfish in aquaria can be a nightmare. Thus, it is unlikely that any adult jellies could survive in ship’s ballast water for any extended period of time, even if they didn’t cleanse it (which they are supposed to do).

Likewise, it is very for an adult to survive intact across the ocean in a plane or some sort of container, even if intended to be brought over.  In my scientific experience, it’s difficult to get jellies to survive an air trip from California to the East Coast, let alone from Australia.

If (and that is a big if) Irukandji has made it over to the gulf and has established itself, it is almost certainly from larvae that have survived the trip.  They don’t have the structural limitations that the adults do- they can survive contact by virtue of their small size and simple structure. This is assuming, of course, that these larvae are similar to the larvae of other Cubazoan jellyfish.  How they would cross the Pacific is unclear, but they may have hitched a ride kudos to the aquarium trade- Australian reef fishes, being beautiful, are sought after for personal and institutional aquaria, and if you ship Nemo with the seawater he was in, well, than you have the possibility of releasing these larvae.

In my personal opinion, I think that Irukandji have probably not reached the Gulf coast, and the ‘attacks’ of this group are in fact coming from other, also very dangerous, box jellies such as the Sea Wasp (Chironex fleckeri). Would these reports of Irukandji stop me from diving in Florida waters? In a word- no.

But then again, I’m not a doctor. (Yet)


Check out more articles on sea creatures, the environment, and other interesting topics coming soon from author Robert Nowicki on CoolDudesDiving.com



Robert Nowicki

Rob! You need to write a mini-bio!