Chironex fleckeri
marine stinger, sea wasp

Chironex fleckeri, also known as box jellyfish, lives in and around the waters of Australia and Southeast Asia. They inhabit parts of the Indian Ocean, Pacific Ocean, and the Great Barrier Reef. Box jellyfish have been found in the waters on the western coast of Australia in the Exmouth Gulf to Gladstone in the northern waters of Australia. Humans are frequently stung by this species in the oceanic waters of Queensland, on Australia's eastern coast. Box jellyfish may also be responsible for stings near the Philippines. (Hamner, 1994; Hamner, 1995; Tibballs, 2006)

Box jellyfish tend to inhabit shallow, murky saline waters near Australia. They are mainly found in the ocean but are also found inland in freshwater rivers and mangrove channels during spawning. During heavy storms, they move into deeper waters where the water is calm to avoid damage. Box jellyfish also inhabit shallow rivers during the reproductive season and during their polyp stage. Once young jellyfish mature into medusa, they follow the river out to sea. (Currie and Jacubs, 2005; Hamner, 1995; Tibballs, 2006)

The name box jellyfish is derived from the shape of their bell, which is box-shaped when healthy. The bell is transparent and is usually between 16 and 24 cm, though some reach a diameter of 35 cm. The tentacles of box jellyfish dangle from pedalia, the corners of the bell. There can be as many as 15 tentacles hanging from each of the four pedalia for a total of up to 60 tentacles per jellyfish. Each of the tentacles has a slight blue-gray tint and can grow up 3 m in length. Each tentacle contains millions of nematocysts, which are microscopic hooks where venom is held and delivered. Box jellyfish contain sensory organs including 24 eyes, but they do not have a brain. (Alderslade, Carrette, and Seymour, 2002; Currie and Jacubs, 2005; Hamner, 1995; Seymour, Carrette, and Sutherland, 2004; Tibballs, 2006)

Because box jellyfish die shortly after spawning, their lifespan is thought to be under a year. The longest lived box jellyfish in captivity survived nine months. Until the invention of a modified tank in the 1990s, it was near impossible to keep box jellyfish alive in captivity for more than a few days. Water is in constant motion in new tanks, allowing box jellyfish to float in the current without being caught in the corners of the tank. (Hamner, 1994; Hamner, 1995; Seymour and Sutherland, 2001; Tibballs, 2006)

Box jellyfish have several behavioral traits that set it apart from other jellyfish. Most notably, box jellyfish can actively swim, whereas most species of jellyfish float wherever the current takes them with no control over their direction. Although box jelly have the ability to move up to 4 knots, during the day they typically travel at 1 knot or less. Box jellyfish usually swim slower during the day than at night, which is likely due to hunting and consuming of prey. Unlike other jellyfish, box jellyfish rest on the sea floor, not moving unless disturbed. Box jellyfish may require this rest phase to energetically compensate for the time they spend actively swimming. Box jellyfish also display this type of behavior when seas are rough, during which they sink to the sea floor until the water calms. Box jellyfish also unintentionally sting humans. The sting of a box jellyfish can be fatal to humans and has accounted for more than 60 deaths in the last 100 years. Most fatalities are documented in children and young adults. (Gordon and Seymour, 2008; Hamner, 1994; Hamner, 1995; Hartwick, 1991; Seymour and Sutherland, 2001; Tibballs, 2006)

Home Range

Box jellyfish have no known home range. (Hamner, 1994; Hamner, 1995)

Because box jellyfish have no brain, it is difficult to define their communication and perception. Box jellyfish do have eyes, which have photoreceptors. Photoreceptors give box jellyfish the ability to detect light from dark, but it is uncertain whether this species can process shapes and figures. Box jellyfish, however, are attracted to light and tend to avoid darker shapes. Box jellyfish can also detect vibrations, which is thought to be useful for finding prey and avoiding predators. Currently, little is known regarding methods of communication between jellyfish. If box jellyfish do communicate with one another, it is most likely through chemical signals. (Coates, 2003; Hamner, 1994; Hamner, 1995)

Adult box jellyfish tend to feed in shallow waters, mainly on small fish and prawns. Until they are fully grown, box jellyfish feed primarily on shrimp, most commonly Acetes australis. Box jellyfish rely on their venomous tentacles to capture their prey. The millions of nematocysts on their tentacles enable box jellies to deliver lethal does of venom to their prey, immobilizing or killing them in a short amount of time. Because each nematocyst is so small and releases only a minute amount of venom, box jellyfish discharge as many of its nematocysts as possible. Once the tentacles capture the prey, box jellyfish bring it in closer to their bell and other tentacles, allowing use of nematocysts from other tentacles to more quickly immobilize and kill the prey. (Alderslade, Carrette, and Seymour, 2002; Currie and Jacubs, 2005; Tibballs, 2006)

Box jellyfish have few known predators because of the stinging cells (nematocysts) on their tentacles. These nematocysts are extremely venomous to most species. The only known predator of box jellyfish are green turtles. Venom does not penetrate the thick skin of green turtles, which are thus unaffected by the stings of box jellyfish. (Hamner, 1994; Hamner, 1995; Seymour and Sutherland, 2001)

Box jellyfish prey on prawns, shrimp, and small fish, though box jellyfish do not greatly affect populations of these species. Green turtles (Chelonia mydas) prey upon box jellyfish, but jellyfish are not their primary source of food. (Hamner, 1994; Hamner, 1995; Seymour and Sutherland, 2001; Tibballs, 2006)

Box jellyfish are believed to be the most venomous creatures in the world. Their stings are extremely deadly to human beings, and have caused over 60 deaths in the last century. The amount of venom injected into humans by box jellies influences the certainty of death. It is estimated that if a total of 6 m of tentacles comes into contact with human skin - and therefore all nematocysts on those tentacles “fire” - the amount of venom injected is sufficient to cause death in just a few minutes. Shortly after a human is stung, they typically encounter symptoms such as extreme pain, shortness of breath, and purple welts. Some victims may also become irrational and suffer cardiac arrest. All of these symptoms typically commence within five minutes of being stung and can last up to two weeks before subsiding. Although box jellyfish are fully capable of killing adult humans, most fatalities are documented in children and young adults. To reduce fatalities, box jellyfish nets have been constructed on many beaches where box jellyfish stings are known to occur. Despite these nets, there are still reports of stings every year. (Coates, 2003; Hamner, 1994; Hamner, 1995; Seymour and Sutherland, 2001; Tibballs, 2006)

The study of box jellyfish venom has led to a successful anti-venom agent, which can save human lives if administered quickly. Additionally, while this research is still in its infancy, scientists hope to better understand why jellyfish venom is so harmful to the human cardiovascular system. Once determined, this information can hopefully be used to design more effective medicine for other cardiovascular problems. (Hodgson and Isbister, 2009; Seymour and Sutherland, 2001; Tibballs, 2006; Winter et al., 2009)

Box jellyfish are not considered at risk by the IUCN, CITES, or the US Federal List. Furthermore, there are no conservation efforts for box jellyfish.