Spineless, brainless, soft bodied, deadly – the Irukandji
The very fact that some of the most dangerous creatures in the sea at first glance seem so… pathetic kind of makes me laugh. I mean seriously, who would have thought that a creature without a spine, brain or even hard body parts could harm, let alone kill someone especially when it is around 13mm across?
Well, enter the Irukandji complex of ‘jellyfish.’ Not true jellyfish, Irukandjis and the related Box Jellyfish belong to the class Cubozoa, a group of invertebrates similar to jellyfish. The coolest thing about these, is compared to true jellyfish, they are the turbocharged versions of their relatives- swift and agile in the water and able to cruise at 2-3 knots. There are many species, and scientists are still figuring out exactly how many there are and which can cause the nasty symptoms of Irukandji syndrome.
It is likely that more species than we currently know may trigger the dreaded Irukandji syndrome.
Another remarkable feature of these creatures are the ribbons of pure death that trail behind them. The tentacles are long, ridiculously so. The true Irukandji species (Carukia barnsei) may have tentacles up to a meter long, towed behind a body the size of a fingernail. The larger Box Jellyfish (Chironex fleckeri) may extend its tentacles up to three meters! The stings are strong, similar to a cotton thread and can be retracted if the animal wishes to speed up or avoid danger. Either way you don’t want to get on the business end of these. The Box Jellyfish can cause rapid death and instant, searing pain along the sting site, but an expert using due care can safely handle one by the body. The true Irukandji has stinging cells on the head as well, so both ends mean business. The scary part is the nature of the venom. Regarded by some to have 100 times the potency of cobra venom, the Irukandji venom may trigger the syndrome by the same name. I have met several people over the years that have personal stories about the horror of a sting. The victims experience pain like never before, affecting many parts of their bodies, a doctor even said that victims were still writhing after receiving general anesthetic! Another said that victims become apathetic and morbid, hoping to die.
|Want to know how all of this was photographed? Check out the article on macro photography here on this site. In case you were wondering I used the Canon EOS 60D, with two wireless flashes, the Canon Speedlite 430EX II and Canon Speedlite 580EX II with the creature safely in an aquarium. The lens was the Canon EF-S 60mm f/2.8 Macro USM.|
There are many Irukandji-like ‘jellyfish’ getting around in the oceans of the world and although tropical Australia seems to be the official home of these creatures, the syndrome has been reported on all of the major continents except South America where it is likely to occur, but never reported.
While the Box Jellyfish seems to like slightly turbid inshore waters, especially near mangroves the Irukandji likes cleaner waters offshore. I had my first encounter with what may have been a cubozoid in North Queensland. While standing on a rock in chest deep water I felt a sting on my side. It felt like a sea louse but on closer inspection was more like a rash which vanished quicky. For the next 24 hours a burning itch spread from that site until from my left shoulder to my ankle felt like I had rolled in fibreglass powder. I couldn’t sleep on that side for about a week. This may not have been the Irukandji, but one of its less dangerous relatives. What is such insanely powerful venom used for? The prey they seek is as dangerous to them. Fish and shrimps are what they feed on, and a struggling spiny prey item can tear the animal apart in a second or two. Luckily for them the struggle doesn’t last that long. I have seen a small fish swim into the tentacles of a larger Box Jellyfish. It barely twitched.
A fascinating fact about cubozoids is that they have eyes. Yep, they can see. It’s not likely to be for finding their prey but for avoiding objects. While wading on Australia’s far northern tip at any one time we could see at least a dozen Box Jellyfish swimming parallel to the shore with amazing precision. I was safe in long trousers and was amazed at how they actively avoided swimming into me. They would turn seaward when they saw me and resume their course once more when they passed. All of this without a true brain!
But the most recent encounter, and a scary one was filming on Snake Island off the tip of Borneo. After sunset we were making our way back to shore and I noticed an Irukandji-like critter in the light of the dive torch. It came straight for the light! I avoided it and saw more. They all made a beeline for the torch. When in the shallows I had a swarm of over 30 of them all crowding around the beam. I avoided a sting, and do not know if they were the true Carukia barnesi or another similar species. I decided to catch one at a later date to find out for sure.
So, in late June 2012, I took a small glass aquarium down to the beach and swam out to sea with a plastic jar. It took about half an hour to find one, but I swiftly shut the jar lid on my first small Cubozoid! Swimming back to shore I photographed it in the aquarium. Not Carukia but another undetermined species it had purple spots on a bell of 22mm in diameter. The tentacles remained retracted in the aquarium, but the pictures still turned out alright.
Releasing it and heading back out to sea I couldn’t find the other, smaller species that looked remarkably like Carukia but caught a true jellyfish instead. I nicknamed it the “Orange Peel Jellyfish” due to its fruity appearance. Not dangerous to humans it seems, this had a small entourage of fish travelling with it. They are juvenile Amberjacks. It’s kind of strange that these little fish will one day be up to 1.5m long and the source of fear for many smaller reef fish. But for now they need to hide in among the tentacles of this Jelly.