Box jellyfish

Box jellyfish are a group of jellyfish with a box-shaped, squarish bell, which gives them their name. They live in warm tropical and subtropical seas. Some species, such as Chironex fleckeri, Carukia barnesi and Malo kingi, have extremely painful venom, and stings can be fatal.

At least 51 species were known by 2018, and more are likely still to be described. Scientists once put them in the same class as ordinary jellyfish, but in 1973 gave them their own class, Cubozoa, because their life cycle and body are different. Their venom is delivered by touching the tentacles, and a few species can kill a person.

Strong swimmers with many eyes

From each of the four lower corners of the bell hangs a stalk with one or more long tentacles. The bell has an inward fold that squeezes water into a powerful jet, so box jellyfish can move faster than other jellyfish, up to about 1.5 metres per second. They have 24 eyes, and some can form images. The tentacles carry stinging cells, and the animals have well-developed eyes.

Danger at the beach

Box jellyfish are sometimes called sea wasps. In parts of Australia beaches are closed in the season when box jellyfish are around,. If stung, a person should get help at once. Their life cycle is also different from other jellyfish: the polyp turns straight into a jellyfish without splitting into stages. The best-known species is Chironex fleckeri, found from the Indian Ocean to the Coral Sea.

On the globe

The model shows a box-shaped jellyfish with long tentacles. Look for it in warm coastal waters.