Resembling an 18th-century warship under full sail, this fascinating balloon like creature is the Portuguese man o’ war (Physalia physalis), also known as the Man-of-war, floating terror, or bluebottle, and is a marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting.
The man o’ war is recognized by its balloon-like float, which may be blue, violet, or pink and rises up to six inches above the water line.
Anyone unfamiliar with the biology of the venomous Portuguese man-of-war would likely mistake it for a jellyfish. Not only is it not a common jellyfish, it’s not even an “it,” but a “they.” The Portuguese man o’ war is a siphonophore, an animal made up of a colony of organisms working together.
A siphonophore is unusual in that it is comprised of a colony of specialized, genetically identical individuals called zooids — clones — with various forms and functions, all working together as one. Each of the four specialized parts of a man o’ war is responsible for a specific task, such as floating, capturing prey, feeding, and reproduction.
Found mostly in tropical and subtropical seas, men o’ war are propelled by winds and ocean currents alone, and sometimes float in legions of 1,000 or more!
The man-of-war comprises four separate polyps. It gets its name from the uppermost polyp, a gas-filled bladder, or pneumatophore, which sits above the water and somewhat resembles an old warship at full sail. Man-of-wars are also known as bluebottles for the purple-blue color of their pneumatophores.
The tentacles are the man-of-war’s second organism. These long, thin tendrils can extend 165 feet (50 meters) in length below the surface, although 30 feet (10 meters) is more the average. They are covered in venom-filled nematocysts used to paralyze and kill fish and other small creatures.
Those tentacles are the reason beaches put up warning signs about the Portuguese man o’ war.
Found mostly in tropical and subtropical seas, man o’ war are propelled by winds and ocean currents alone, and sometimes float in legions of 1,000 or more!
As trouble can sometimes come in an attractive package, this beautiful creature is sure to attract curious people wandering the beach.
If you are ever so unfortunate to be stung by one, the pain is really indescribable. And those tentacles are not something you want wrapped around your torso and legs either. So beach wanderers be warned: The stalwart man o’ war may still sting you even weeks after having washed ashore.
You wouldn’t be the first person to be fooled by the beauty of this blue, pink or violet bubble.
Indo-Pacific Portuguese Man-Of-War (PDF). Marine Life Profile. Waikïkï Aquarium at the University of Hawai‘i-Māno. 1998. Archived from the original (PDF)
Bluebottles and Pacific man-o-war Stinging jellyfish in tropical Australia. CRC Reef Research Centre. November 2004. Archived from the original
Bluebottle factsheet. Western Australian Museum. Archived from the original