Tentacles of death: The most poisonous jellyfish species in the world
Published: Friday, Feb 2nd 2024, 07:50
Retour au fil d'actualité
A tiny species of jellyfish has recently hit the headlines in Australia: Irukandji. The cnidarian's toxin can trigger a life-threatening syndrome. But it can be even more poisonous.
Zoe Cahill's skin is covered all over with red scars. They bear witness to the ordeal that the young Australian went through last year. The fact that she is still alive is nothing short of a miracle. The welts that run across her body like bloody veins are from the tentacles of a sea wasp - one of the most poisonous animals in the world. Cahill was only about 50 meters from the shore in October when she encountered the creature while on vacation on the Thai island of Koh Phangan.
"A sting from this species of jellyfish can kill you in less than five minutes, and we estimate that a single animal has enough venom to kill hundreds of people," says molecular biologist Greg Neely, who researches the toxins of cnidarians at the University of Sydney. "The venom of the sea wasp virtually punctures holes in the skin and then leads to cell death. This causes severe pain and later leads to scarring." Within a few minutes, the venom can lead to cardiovascular failure.
Like electricity in the body
"Western doctors assured my family that my chances of survival were virtually zero," Cahill wrote on Instagram, where she recounted the stitches and her rescue. She doesn't know exactly how she made it ashore despite the agonizing pain. She was later told that helpers there had poured liters of vinegar onto her already lifeless body, which had turned completely blue, and resuscitated her using heart massage and mouth-to-mouth resuscitation. Cahill told 9News that the sting felt "like electricity was shooting through my body".
Box jellyfish are called the dangerous cube jellyfish in their Australian homeland, and the name alone makes swimmers, snorkelers and surfers alike cringe. The animals are mainly found on the north and east coast of Australia, predominantly in shallow waters. However, they can be found throughout the Indo-Pacific.
There have been several fatal encounters in Thailand in recent years. In 2015, a young German woman died there after being stung by a sea wasp. But Chironex fleckeri, as they are scientifically known, are not the only jellyfish that can put people's lives in danger.
Unexplored Irukandji syndrome
Just recently, another species of jellyfish caused alarm around the famous vacation island of K'gari (formerly Fraser Island): Irukandji. Within a few days, several tourists were stung, including children. The almost transparent cube jellyfish (Carukia barnesi) are tiny and have a diameter of only one to two centimetres - but four tentacles up to one meter long. By comparison, the much larger sea wasp has 15 tentacles at each corner of its bluish swimming bell, each of which can reach up to three meters in length.
The victims on K'gari had to be rescued by rescue helicopters. The mother of one of the victims said: "My son started vomiting and said he could no longer feel his leg. It was scary." The tricky thing is that, unlike box jellyfish, the symptoms usually appear after a delay of around 30 minutes.
The jellyfish's stinging venom can then trigger the so-called Irukandji syndrome - a poisoning that can cause severe abdominal, chest and back pain as well as pulmonary edema. Without medical care, there is a risk to life.
"The Irukandji jellyfish probably poses the greater threat to human safety because it is so small that it cannot be seen and it is often found in less remote places than the cube jellyfish," expert Georg Neely told the German Press Agency. Because of its small size, it is extremely difficult to get enough venom for a scientific study. "Therefore, much less is known about the Irukandjis and the Irukandji syndrome."
Study on antidote
The situation is different with the sea wasp: in 2019, Neely and a team succeeded in producing an agent that can block the effect of the toxin. However, it must be administered within 15 minutes of contact with the sting. Using a specific type of genetic research, the researchers found out which cells were attacked by the toxin and which survived - the antidote worked in mice. However, no clinical trials have yet been carried out in humans.
According to Neely, the relevant authorities have so far been reluctant to conduct such a study due to the high costs involved. "This is because very few people are stung by box jellyfish in Australia every year," he says. Instead, the scientists were advised to find antidotes for toxins that affect more people - such as those of the jellyfish species Physalia physalis or the spitting cobra. The team has now developed antidotes for both toxins, says Neely.
50 meter long tentacles
Portuguese man o' wars, which are not only found in the Pacific, but also off the Canary Islands and around Portugal, are also highly poisonous jellyfish. They have even been spotted off Mallorca.
These are not real jellyfish, but huge polyp colonies in which each individual performs a specific task. Anyone who comes into contact with the tentacles, which can be up to 50 meters long, also suffers severe pain and red welts on the skin. For humans, however, an encounter with the cnidarian is rarely fatal - except in the case of allergic shock.
Neely himself has also been stung by a Portuguese man o' war. It didn't have any serious consequences for him, but the fear was great. "What fascinates me so much is that Australia has all these crazy, deadly jellyfish that make large parts of our coastline completely unusable all year round - and we don't even really know how their toxins work."
©Keystone/SDA
French 
English 
German 
Spanish 
Arabic