The Gonionemus clinging jellyfish can deliver a powerful sting. While they are believed to be native to the North Pacific, the tiny creatures – less than 25 mm across – are found off coasts across the Pacific and Atlantic, and the sting of the Vladivostok clinging jellies, in particular, is known for causing severe pain as well as respiratory and neurological symptoms.
In recent years similar stings have been reported off the east coast of the US. New research suggests that there may be more than one species of the jellyfish, but how the species move from place to place is still a mystery.