Chirodropid Jellyfish and Jellyfish Venom

Chirodropid jellyfish have multiple tentacles hanging from each corner of their box-shaped bodies. They usually have stinging cells only on their tentacles. These jellyfish are smaller than Chironex and have up to nine tentacles from each corner of the bell. Only one species of Chiropsalmus was thought to occur in Australia (mistakenly called Chiropsalmus quadrigatus). Now thought to be several different species that are yet to be named. The sting is painful but does not cause Irukandji syndrome.

Chironex fleckeri Jellyfish

Large, almost transparent jellyfish up to 380mm across, Up to 15 tentacles from each corner of its box-shaped body, Found in tropical waters from Exmouth,WA to near Gladstone, Queensland, Found near the coast and some coastal islands such as Magnetic Island near Townsville and some inshore Whitsunday Islands, Severe and potentially life-threatening sting that causes burning skin pain. Severe stings may cause the victim’s breathing to cease or the heart to stop.

Unlike many jellyfish, the multiple-tentacled box jellyfish Chironex fleckeri is a fast and agile swimmer and is rarely ever found washed up on beaches. It can swim at up to three knots and manoeuvre around pylons and piers. Although Carukia barnesi is also a box jellyfish, it is not as proficient at swimming as Chironex fleckeri. All cubozoans have eyes so that they can hunt prey and avoid objects in the water. Each jellyfish has 24 eyes clustered into four groups of six on each side of its box-shaped body. There are two types of eye in each cluster two complex eyes similar to human eyes (with retinas, lenses and corneas) and two simple pit eyes and two slit eyes. Although cubozoan jellyfish do not a have a brain (they have neurons concentrated in four nerve centres), recent studies indicate that they can form images.

Jellyfish also have organs called statocysts located below the eye clusters that help them maintain balance in the water. Inside each statocyst is a hard nodule called a statolith that is composed of calcium sulfate. In many species of box jellyfish, statoliths have daily growth rings and can be used for ageing them. It may also be possible to use statoliths to identify jellyfish species when their soft body parts are destroyed.

Carybdeid Jellyfish

Carybdeid jellyfish usually only have a single tentacle hanging from each corner of their box-shaped bodies. They have stinging cells on both body and tentacles.


Carybdea rastonii, jimble (About 15-40mm tall and Found in southern waters from Coffs Harbour, NSW, to Albany, Western Australia)


Carybdea xaymacana (Similar to Carybdea rastonii but smaller, rarely more than 15-25mm tall and Common off Perth, from Busselton to Geraldton. Also found in Cairns region)


Carybdea sivickisi (Up to 8mm tall, with adhesive pads on top of body, and orange and brown striped tentacles and Common in algal beds of Magnetic Island near Townsville, the Whitsundays, Tasmania and South Australia)


Tripedalia Binata (Bell usually less than 10mm, with two tentacles on each corner and Found near Darwin,Weipa and Cairns, typically among mangroves)

Jellyfish Feeding & Venom

Box jellyfish feed on fish, crustaceans and other marine invertebrates. They use potent venom to quickly kill their prey so that it does not escape. The venom is contained in stinging cells called nematocysts. Most box jellyfish have several different types of nematocysts; the type and proportion of nematocysts can be used to identify some species. The stinging cells have a miniature harpoon coiled inside them which is everted (turned ‘inside –out’) when the jellyfish contacts its prey. The bulb of the nematocyst injects toxin through the shaft and into the prey. The tentacle is contracted, and the pedalia (oar-like structures at the base of the tentacles near the bell) push the food into the manubrium or mouth which is located inside the bell. Once the nematocysts are fired, the jellyfish has to produce new nematocysts to replace them.


Chironex fleckeri has tentacles that can be extended to more than three metres long. There are billions of nematocysts along each tentacle. When Chironex fleckeri is young and eating mostly prawns, only five percent of the nematocysts contain venom which is potent to vertebrates. However, as the jellyfish grows and its diet switches to fish, the proportion of vertebrate-potent venom increases and can be found in 30-40 percent of the nematocysts.

Chironex fleckeri has tentacles that can be extended to more than three metres long. There are billions of nematocysts along each tentacle. When Chironex fleckeri is young and eating mostly prawns, only five percent of the nematocysts contain venom which is potent to vertebrates. However, as the jellyfish grows and its diet switches to fish, the proportion of vertebrate-potent venom increases and can be found in 30-40 percent of the nematocysts.


The box jellyfish Chironex fleckeri are the most venomous marine creatures on the planet and, in
Australia, have killed almost 70 people in the last 120 years. In the Northern Territory, fatal box
jellyfish stings have been reported in every month of the year except August. Most stings occur in shallow water when the wind is light and the water calm (although stings have occurred in rough weather, in very dirty, deeper water). Victims usually blunder into tentacles trailing behind the jellyfish which are almost invisible in the water. Most stings occur on the lower legs and body.


Pain is instant and severe. The tentacles are like sticky threads and leave raised red marks. The venom of the box jellyfish is neurotoxic (attacks nerves), cardiotoxic (attacks the heart) and dermatonecrotic (destroys skin). Therefore, victims can rapidly stop breathing, sometimes within a few minutes of the sting. Death occurs rapidly unless prompt first aid and medical aid is available. If the victim survives, they are often scarred. Treating the sting sites as if they were burns greatly reduces the scarring, suggesting that it may be secondary infections that cause the scarring.

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