Irukandji Jellyfish: Habitat & Facts

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

There are a number of species in the box jellyfish group. In this lesson you'll learn about the habitat of one species, the Irukandji jellyfish, as well as some interesting facts about them.

The Irukandji Jellyfish

When you think about animals in the ocean, what comes to mind? Maybe whales, fish, or other large animals. What about jellyfish? There are hundreds of species of jellyfish, ranging from teeny tiny up to as big as a blue whale. The box jellyfish, or Cubozoa, are in the smaller group, and this group contains one particularly interesting species: the Irukandji jellyfish, or Carukia barnesi.


The Irukandji jellyfish is one of the smallest jellyfish species. On average, its bell, or main section, is less than one inch across! In addition, it is nearly transparent, which makes it extremely difficult to see in the water.

This jellyfish has four tentacles, one attached to each corner of its square-shaped bell. The cubic bell shape is where the box jellyfish group actually gets its name. Interestingly, the Irukandji's tentacles are retractable, which is unusual.


Like most box jellies, Irukandji live in warm waters. Specifically, they are found off the Northern coast of Australia, along the Great Barrier Reef. Irukandji are found in deeper water, farther from shore than most other box jellyfish species. This is not to say they live in the open ocean. The Great Barrier Reef is enormous and has many deeper sections. Irukandji live in water that is 33 to 66 feet deep. They are occasionally found in shallower water, but only when pushed there by the current or tide.

The Great Barrier Reef is the largest coral reef system in the world
Great Barrier Reef

Toxic Sting

One interesting aspect of the Irukandji jelly is its sting. Irukandji jellyfish have nematocysts, or stinging cells, on their tentacles like most jellyfish. However, they also have them along their body. There is really no safe way to touch one of these!

In addition, Irukandji venom is highly toxic. They use it to stun or kill their prey so they can eat it. Despite their tiny size, an Irukandji sting can kill an adult human. However, a healthy person can survive if they are hospitalized in time.

The reaction to the sting of an Irukandji is so distinct that it has a name: Irukandji syndrome. A person struck can have symptoms like nausea, shooting muscle pains, and fluid in the lungs.

Other Interesting Facts

Moving past its extreme toxicity, the Irukandji is quite the interesting creature. For one thing, scientists do not know its lifespan. They might guess based on other Cubozoans, but they do not know for sure.

Another interesting fact is how delicate the Irukandji is. It cannot be kept in a normal aquarium because if it hits the glass, it will die. Think about that: this little jellyfish can kill a human, but it can't survive drifting into a glass wall.

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