The Portuguese man o' war (Physalia physalis), also known as the, Man-Of-War, or bluebottle, though often mistaken as a jellyfish, is a marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting.
Despite its outward appearance, the Portuguese man o' war is not a jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single multicellular organism but a colonial organism made up of many highly specialized minute individuals called zooids.
These zooids are attached to one another and physiologically integrated to the extent that they are incapable of independent survival.
This species and the smaller Indo-Pacific man o' war (Physalia utriculus) are responsible for up to 10,000 human stings in Australia each summer, particularly on the east coast, with some others occurring off the coast of South Australia and Western Australia.
The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o' war can paralyze small fish and other prey.
Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.
Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last 2 or 3 days after the initial sting, though the pain should subside after about an hour.
However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, a more intense pain.
A sting may lead to an allergic reaction. There can also be serious effects, including fever, shock, and interference with heart and lung function. Stings may also cause death, although this is extremely rare.
