When visiting Northern Australian beaches, there are many signs warning tourists about stingers, however the majority of jellyfish cannot actually sting you. So, what are stingers? Generally, these signs are referring to Box Jellyfish and their smaller cousin, the Irukandji.
The Box Jellyfish (Chironex Fleckeri) is claimed to be the most venomous marine animal. It has a cube-shaped bell, measuring up to 20cm-cubed, with tentacles reaching up to 3 metres in length. There are up to 15 tentacles on each corner, with each comprising thousands of stinging cells. They are transparent and pale blue in colour, making them invisible in the water. True jellyfish drift on ocean currents, while the box jellyfish propels itself forward in a jet like motion, reaching speeds up to 3 or 4 knots, which is the equivalent of 1.5 to 2 metres per second. Clusters of eyes are located on each side of the box. Their speed and vision leads researchers to believe that they actively hunt their prey, rather than waiting for prey to “bump” into their tentacles.
Box Jellyfish like to hang out around river mouths, estuaries and creeks, especially after rain, which is why there are frequent incidents from October / November until March. But they don’t like deep waters and rough seas, so luckily for us, they’re generally absent on the Reef and over other areas that have lots of sea grass. In late summer, they spawn in the river mouths that they like so much, with the larval polyps attaching themselves to rocks, where they develop until spring. Once spring arrives, the polyps turn into tiny jellyfish and are washed downstream with the summer rains.
A sting from a box jellyfish has severe consequences, as the toxins affect the heart (cardiotoxic), damages the nerves (neurotoxic) and effects the skin (dermatonecrotic). If victims have had extensive contact with the tentacles, they can go into cardiac arrest within minutes. Even a slight touch can cause excruciating pain that the victim immediately goes into shock. Severe stings can leave behind nasty scars, as the tissue gets eaten away. The most important thing to do is to inactivate the remaining stinging cells by pouring vinegar over the tentacles, allowing them to soak for 30 seconds, before removing them from the victim.
Irukandji on the other hand, are no bigger than a thumbnail. These jellyfish only have one tentacle on each corner instead of 15. Symptoms from an Irukandji sting appear 5 to 45 minutes after the incident and include lower back pain, muscle cramps, sweating, nausea, vomiting, restlessness, anxiety and palpitations. In the most severe cases, people developed pulmonary oedema (water in the lungs), hypertension and toxic heart failure. The treatment is the same as for Box Jellyfish.
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