The Portuguese Man O’ War (Physalia physalis), also known as the Portuguese Man-Of-War, Man-Of-War, or Bluebottle, is a jellyfish-like marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a powerful sting.
The Portuguese man o’ war lives at the surface of the ocean. The gas-filled bladder, or pneumatophore, remains at the surface, while the remainder is submerged. Since the man o’ war has no means of propulsion, it is moved by a combination of winds, currents, and tides
The Portuguese man o’ war is composed of four types of polyp. One of the polyps, a gas-filled bladder called the pneumatophore (commonly known as the sail), enables the organism to float. This sail is bilaterally symmetrical, with the tentacles at one end, and is translucent, tinged blue, purple, pink or mauve. It may be 9 to 30 centimeters (4 to 12 in) long and may extend as much as 15 centimetres (6 in) above the water.
The other three polyp types are known as dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding). These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 metres (30 ft) in length but can be up to 50 metres (165 ft). The long tentacles “fish” continuously through the water, and each tentacle bears stinging, venom-filled nematocysts (coiled, thread-like structures), which sting and kill small sea organisms such as small fish and shrimp.
The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o’ war can paralyze small fish and other prey.
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.
The imperial blackfish S. ovalis is a subtropical species with a
wide geographic distribution reported from the eastern Atlantic, western central Atlantic, and the Mediterranean
Young are epipelagic and associate with floating jellyfish, including Physalia. (via)