The most common Mediterranean jellyfish, Pelagia Noctiluca, not dangerous but possesses an uncomfortable sting. Photo by Hans Hillewaert.
There are around two thousand species of Jellyfish in the world but less than one hundred are considered dangerous to human animals. They are not in fact fish but invertebrates with none of the organs we would associate with higher life forms.
Jellyfish eat mainly zooplankton and do so by capturing them with toxic tentacles which range from a few inches to a few hundred feet long. They travel around the oceans via self propulsion, tide and wind, in warm and cold waters alike.
The lack of a brain in your average jelly means that if a jellyfish stings you it really can’t help it – unless it’s Chironex Fleckeri (Box Jelly) which can apparently herd fish and shrimp into the shore.
When Jellies’ stinging cells (nematocysts) make contact with your skin they fire their poison into it via tiny harpoons.
The Box jelly species, known as Sea Wasps or Cubozoa (ie. cube shape), includes Irukandji as far as scientists are concerned, though laymen think of the Box jelly as the big one and Irukandji as the little ‘un. The biological names are: Chironex Fleckeri (the Box) and Carukia Barnesi (the Peanut)
Box Jellyfish (Toxic Boxes)
Box Jellyfish photo by Guido Gautsch
The Box Jelly (aka Sea Wasp or Chironex Fleckeri) is the most toxic creature on Earth. They and 20 close relatives are found off the shores of Northern Australia, PNG, Malaysia, Indonesia, the Philippines, Thailand and Vietnam.
This pale blue creature has a boxy bell head the size of a basket ball, 24 eyes and 5,000 stinging cells on each of its fifteen 3 metre long tentacles.
Some researchers believe that groups of Box Jellies deliberately herd small fish and crustaceans towards the shore in order to trap them, thus bringing them into contact with humans.
New Scientist magazine in 2003 revealed that Box jellies are not ‘dim-witted ocean drifters’ but ‘fast, active predators that hunt and kill with incredible speed and brutality.’
The Toxic Box is responsible for at least one death a year around Australia and has killed 67 people since records began in 1883, though the total is misleading since many deaths attributed to heart attacks or drowning could have been caused by toxic jellies.
Problem shores are usually signposted, and this is one serious bubblepack to be avoided at all costs – the most poisonous creature in the world.
The Box Jelly is mostly a problem from October – May, in the daytime.
• severe pain
• headache, nausea, vomiting, diarrhoea
• skin swelling/wounds/redness
• difficulty breathing, swallowing and speech
• shivering, sweating
• irregular pulse/heart failure
A fully grown and highly venemous Irukandji jellyfish, Australia
Irukandji (Carukia barnesi and several other unidentified species that produce Irukandji Syndrome) also lurks in the waters of Northern Australia, mostly near Cairns and the Great Barrier Reef. Irregular sea currents can easily move it to the shore.
Irukandji is extremely painful and occasionally deadly and has been seen as far south as Brisbane. It’s mostly a problem from November – May, but has been recorded in all months except July and August.
Symptoms (as little as 5 minutes after apparently mild stings)
• lower back pain, intense headache.
• muscle cramps and shooting pains, nausea, vomiting.
• catastrophically high blood pressure.
• restlessness and feeling of impending doom.
• death from heart failure or fluid on the lungs.
Portuguese man o’ war. Photo by Haplochromis.
Also known as the Blue Bottle by Australians or Hydrozoa to a scientist, this is a sail bearing, wind blown animal which travels the Atlantic, Pacific and Indian Oceans and may be blown inshore. I’m one of thousands who have not enjoyed Blue Bottle contact (off Cairns and Manly beach, Sydney) but really, not a big problem, probably less painful than a bee sting depending on how many tentacles you encounter and which part of your body it was. The larger varieties may be occasionally fatal to delicate humans but are not usually dangerous.