Class: Cubozoa

Box-shaped jellyfishes

The box jellies are squarish animals that have long tentacles dangling from the lower corners of the box. Each tentacle may diverge into dozens of thinner tendrils, each containing millions of stinging cells called nematocysts. 

These animals generally feed upon fishes, and are capable of swimming quite quickly. Surprisingly, though, their venoms are extremely potent. The venom of the Australian sea wasp (Chironex fleckeri) is considered to be the most toxic of all known animal venoms, and many swimmers have died only minutes after being stung by sea wasps.

Suggested Reading:

Seymour, Jamie. 2002. One touch of venom: a box jellyfish is a killer without peer. Natural History 111(7): 72-75.