Australian box jellyfish (Chironex fleckeri) have large, cube-shaped bells (up to 30-38 cm or about a foot wide) that are pale blue and nearly transparent, with multiple long tentacles extending from each corner that can stretch up to 3 meters (10 feet) long, making them hard to spot in the water but incredibly dangerous due to their potent venom.
They measure up to 38cm across. Each corner of the body contains up to as many as fifteen tentacles each 3 metres in length. With a small set of eyes, these jellyfish are capable of sight. The Box Jellyfish moves at speeds of 4 knots in a jet-like motion.
Box jellyfish have venom in their tentacles that can sting and kill a person in under five minutes. Children are also at greater risk because of their smaller body mass. Since 1975, there have been 14 deaths in the Top End - all children.
Victims usually survive minor stings from box jellyfish. Experts say that Rachael is the only person to survive such serious stings. The jellyfish's venom quickly attacks the heart and muscles. It also attacks the nervous system, which contains your brain, spinal cord, and other nerves in your body.
The largest species of box jelly is Flecker's sea wasp Chironex fleckeri, with a cuboidal bell that can measure up to 30 cm in diameter, and 60 tentacles that can each measure up to 3 m long in fully extended form when hunting.
There are thousands of box jelly stings per year, and of those only 20-40 are fatal.
Predator and prey adaptations
They mainly eat krill, plankton and even other jelly fish. The box jellyfish as no prey adaptations. Its only predator is the Green Sea Turtle because it's thick skin is not effective to the venom and don't have other ways to fight it off.
The box jellyfish (like the Sea Wasp) is generally considered more immediately dangerous due to its larger size, longer tentacles, and ability to cause rapid death (minutes) from cardiac arrest, while the tiny Irukandji (a type of box jellyfish) has more potent venom per volume and causes "Irukandji syndrome" with delayed, severe pain, muscle cramps, and blood pressure spikes, but is less likely to kill as quickly unless many stings occur. Box jellyfish kill faster, but Irukandji venom is incredibly potent, though often requires multiple stings to be fatal.
They don't have a brain like we do – just a network of nerves with sensory receptors that detect changes to their environment. So, when a jellyfish moves or reacts, it's largely driven by automatic reflexes, not the kind of conscious decision-making we associate with sentience.
Major box jellyfish
Their tentacles are very long and likely to touch more of your skin. A sting from a major box jellyfish can cause severe pain and red, whip-like lines. If you get a bad sting, your heart may stop, causing death. This can happen in 20 to 30 minutes.
Green sea turtles in particular are the major predator of the box jelly. In fact, they may be the only natural predator of this type of jellyfish.
While box jellyfish are found in warm coastal waters around the world, the lethal varieties are found primarily in the Indo-Pacific region and northern Australia. This includes the Australian box jellyfish (Chironex fleckeri), considered the most venomous marine animal.
If you do spot them, their cube-shaped bell, which gives them their name, is a tell-tale giveaway that a box jelly is swimming towards you. And, unlike other jellyfish, they actively swim rather than just drifting along in the water.
Minimize unprotected areas. Wear full exposure suits, hoods, boots and gloves. Something as simple as nylon pantyhose worn over the skin can prevent jellyfish stings. Carry sufficient household vinegar with you to all dive sites.
Age and growth
The maximum age of any individual examined was 88 days by which time it had grown to an IPD of 155 mm (6 in). In the wild, the box jellyfish will live up to 3 months, but can survive up to seven or eight months in a science lab tank.
Box jellyfish (Cubomedusae) possess a unique visual system comprising 24 eyes of four morphological types.
Jellyfish can clone themselves
Yep, that's right – if a jellyfish is sliced in half, the two pieces can regenerate and create two new organisms.
No, jellyfish have no single centralized brain. Instead, they have radially distributed nervous systems that are adapted to their unique body plan.
The creature that is 98% water is the jellyfish, a gelatinous marine invertebrate whose bell-shaped body is largely composed of water, giving it a translucent, blob-like appearance and low energy needs for growth. This high water content (sometimes cited as 95-98%) allows them to be buoyant and drift, making them an evolutionary success story in the oceans, according to NOAA's National Ocean Service and National Geographic.
Irukandji jellyfish's stings are so severe they can cause fatal brain hemorrhages and on average send 50–100 people to the hospital annually. Robert Drewe describes the sting as "100 times as potent as that of a cobra and 1,000 times stronger than a tarantula's".
Stinger suits are full body suits designed to protect you from stingers such as blue bottles and Irukandji.
Synanceia verrucosa, a species of stonefish, is lined with dorsal spines that deliver an intensely painful and lethal venom. It is sometimes called the most venomous fish in the world.
The diet of the box jellyfish includes plankton, small fish, and prawns, or shrimp-like crustaceans. Its favorite food is shrimp.
A dead jellyfish still can sting, so wear sandals even on the sand. If you're stung, rinse off the affected area using either seawater or hot tap water. This will help remove the stinging cells the jellyfish can leave.
Turtles are the only jellyfish predators
Thanks to a thick skin, turtles are not affected by box jellyfish stings. In fact, only their eyes can be stung.