Amakusa jellies are small, disc-shaped jellies of the Pelagiidae family - a large group of jellies that include the common compass jelly. Their umbrellas grow to about nine cm across and, in some cases, have warty protrusions on top which contain stinging nematocysts. They vary in colour from pale brown to white. Amakusajellies are primarily jellyvorous, meaning they eat other jellies, but will opportunistically prey on almost anything. Their sting is powerful, can kill most small fish within seconds, and is highly toxic to humans. It is not known how they identify members of the same species, but somehow Amakusa jellies avoid eating each other. Amakusa jellies occupy the Indian Ocean and the western Pacific Oceans, ranging from the African east coast to Japan, Oceania and New Zealand.