There are fifty-one species of box jellyfish around the world. They can be grouped into two orders and eight families. Their venom is one of their best-known features. It is incredibly dangerous to most animals, including humans. It can kill a human being in as little as two minutes. Rarely does someone who was stung by a box jellyfish live to tell about it. Often, these jellyfish are regarded as the world’s most venomous creatures.


The jellyfish has a squarish bell that boasts four pendulums, one on each corner. There, the jellyfish also has slim tentacles. The animal can grow up to eight inches along each side of the box, with a twelve-inch, or thirty centimeters, diameter. The tentacles can grow to an impressive length of ten inches. Usually, the jellyfish only weighs around four and a half pounds. 

Underneath the bell is a manubrium, a mobile appendage that bears some resemblance to an elephant’s trunk, with a mouth at the tip. The inside of the bell is divided into four equidistant septa. Inside are a central stomach and four gastric pockets. The nervous system is more developed than other jellyfish species. It is defined by a ring of nerves around the base of the jellyfish’s bell. This helps with their movements. 

Halfway up the outer surface of the bell are their eyes, set in clusters called rhopalia. The animals can see specific points of light due to the direction of the lenses. In total, they have twenty-four eyes. Their increased sight allows them to navigate around obstacles in a way that other jellyfish can’t. They also swim faster and with more determination. This is likely due to the fact that they can more clearly see what’s ahead of them. 

Interestingly, box jellyfish do not have brains. Instead, they rely on neurons that send signals throughout their bodies. This helps them determine where to go, what to eat, and what is dangerous or safe. 

The sea wasp jellyfish, a type of box jellyfish
The sea wasp jellyfish, a type of box jellyfish


These jellyfish are found around the world, but the most dangerous variety is usually found in the tropical Indo-Pacific region. It is not uncommon to find most species in the Atlantic Ocean and the eastern Pacific Ocean, as far north as California. They are also found in the Mediterranean Sea and the Sea of Japan. There are three species in the waters around Hawaii as well. 

The most dangerous species of box jellyfish are Chironex fleckeri, Carukia barnesi, Malo kingi, among a few others. These species are found mainly in the Indo-Pacific region. Their stings can be extremely dangerous and painful to human beings. They are often fatal as well.


The jellyfish is known for actively hunting its prey rather than drifting and eating what it comes upon, as some other jellyfish do. They can reach higher speeds than other species, as noted above (up to one and a half to two meters per second). They use their tentacles to reach and stun their prey. This includes fish, shrimp, crustaceans, and other small species of jellyfish. 


The box jellyfish uses reproductive methods that are similar to those employed by other jellyfish species. This includes releasing eggs and sperm into the water or placing the sperm inside the bell of the female. The fertilized eggs become larvae and can swim around before settling on a hard surface, where they develop into polyps. While in this form, the jellyfish can reproduce asexually through budding.

"Cubomedusae" by Ernst Haeckel's
“Cubomedusae” by Ernst Haeckel


The box jellyfish have very few predators of a serious nature due to their venom. 

They can use their deadly tentacles to defend against most larger sea creatures. Interestingly, there are some species of sea turtles that appear to be immune from box jellyfish venom. Some predators they have to define against include triggerfish, sunfish, seabirds, whale sharks, some crabs, and other species of whales. 

Vinegar for jellyfish stings
Vinegar for jellyfish stings

Facts about the Box Jellyfish 

  • The box jellyfish is named for its box-like shape
  • The box jellyfish has very few predators. 
  • The jellyfish is known for actively hunting its prey. 
  • The most dangerous species of box jellyfish are  Chironex fleckeri, Carukia barnesi, Malo kingi. 
  • Their stings can be extremely dangerous, painful, and often fatal to human beings. 
  • Their diet includes fish, shrimp, crustaceans, and other small species of jellyfish.


Is a box jellyfish deadly?

Yes, the box jellyfish is incredibly deadly. There have been a number of reported human deaths caused by box jellyfish venom. Death can occur in as little as two minutes after being stung by this animal. 

Has anyone survived a box jellyfish sting?

Yes, one survivor includes a 10-year-old girl who survived an attack. But, they are very few cases of human beings coming into contact with this venomous creature and living to tell the tale.

Is the box jellyfish the deadliest animal in the world?

It is certainly among the deadliest. Luckily, it is not a threat unless one is in specific areas of the world’s oceans. 

Is it legal to own a jellyfish?

Yes, it is legal to own a jellyfish. There are a few things, including a big saltwater tank, that you will need to keep a jellyfish. Box jellyfish specifically make poor pets due to the fact that they will kill everything else in the tank.

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