Portuguese man o’ war (Physalia physalis)

The Portuguese man o’ war is a marine hydrozoan found in the Atlantic, Indian and Pacific Oceans. It is one of two species in the genus Physalia, along with the Pacific man o’ war. Physalia is the only genus in the family Physaliidae. Its long tentacles deliver a painful sting, which is venomous and powerful enough to kill fish and even humans. Despite its appearance, the Portuguese man o’ war is not a true jellyfish but a siphonophore, which is not an individual multicellular organism (true jellyfishes are single organisms), but a colonial organism made up of many specialized animals of the same species, called zooids or polyps. These polyps are attached to one another and physiologically integrated, to the extent that they cannot survive independently, creating a symbiotic relationship, requiring each polyp to  work together and function like an individual animal. The Atlantic 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. Portuguese men o’ war have no means of propulsion, and move driven by the winds, currents, and tides. This species is 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. One of the problems with identifying these stings is that the detached tentacles may drift for days in the water, and the swimmer may not have any idea if they have been stung by a man o’ war or by some other less venomous creature. The Portuguese man o’ war is a carnivore. Using its venomous tentacles, a man o’ war traps and paralyzes its prey while “reeling” it inwards to the digestive polyps. It typically feeds on small marine organisms, such as fish and plankton.

photo credits: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Joi Ito , Biusch