The Portuguese Man o' War (Physalia physalis), also known as the blue bubble, blue bottle, man-of-war, or the Portuguese man of war, is a jelly-like, marine invertebrate of the family Physaliidae.
The common name comes from a Portuguese war ship type of the 15th and 16th century, the man-of-war or caravel (in Portuguese, Caravela), which had triangular sails similar in outline to the bladder of the Portuguese Man o' War.
While the Portuguese Man o' War resembles a jellyfish, it is in fact a siphonophore: a colony of four kinds of minute, highly modified individuals, which are specialized polyps and medusoids.
The Portuguese Man o' War is infamous for having a painful sting, and for swarming in many hundreds. It is responsible for up to 10,000 stings in Australia each summer, particularly on the east coast, with some others occurring off the coast states 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 which wash up on shore) can sting just as painfully as the live creature in the water, and may remain potent for hours or even days after the death of the creature or the detachment of the tentacle.
Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin which normally last about 2 to 3 days after the initial sting, although the pain should subside after about 1 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 action. Stings may also cause death, although this is rare. Medical attention may be necessary, especially where pain persists or is intense, or there is an extreme reaction, or the rash worsens, or a feeling of overall illness develops, or a red streak develops between swollen lymph nodes and the sting, or if either area becomes red, warm and tender.
Research suggests that in the normal course the best treatment for a Portuguese Man o' War sting is: