Portuguese Man o' War

The Portuguese Man O' War (Physalia physalis), also known as the bluebubble, bluebottle or the man-of-war, is commonly thought of as a jellyfish but is actually a siphonophore—a colony of specialized polyps and medusoids.^[1]

A similar group of animals are the chondrophores.

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Structure

The Man O' War's float is bilaterally symmetrical with the tentacles at one end, while the chondrophores are radially symmetrical with the sail at an angle. Also, the Man O' War has a siphon, while the chondrophores do not.

The Portuguese Man O' War has an air bladder, known as the pneumatophore or sail, that allows it to float on the surface of the ocean. It has no means of propulsion and is pushed by the winds and the current. The sail is filled with air, but may build up a high concentration of carbon dioxide (up to 90%). The bladder must stay wet to ensure survival; every so often it may roll slightly to wet the surface of the float. To escape a surface attack, the pneumatophore can be deflated allowing the Man O' War to briefly submerge.

Below the main body dangle long tentacles, sometimes reaching ten meters (33 feet) in length below the surface, although one meter (three feet) is the average. They sting and kill small sea creatures such as small fish and shrimp using venom-filled nematocysts then draw the prey in to the gastrozooids, another type of polyp that surrounds and digest it. Gonozooids are responsible for reproduction.

Venom

The sting from the tentacles is dangerous to humans; these stings have been responsible for several deaths, but usually only cause excruciating pain. Detached tentacles and specimens which wash up on shore can sting just as painfully as the intact creature in the water for weeks after their detachment. The venom can travel up to the lymph nodes and may cause, depending on the amount of venom, more intense pain. In extreme cases medical attention is necessary.

Research suggests that the best treatment for a sting is to apply hot water (45°C/113°F) to the affected area, which eases the pain of a sting by denaturing the toxins.^[2] Ice is also effective at suppressing the pain through reducing the activity of the toxins and reducing the sensation and therefore pain of the area of skin around the ice. Additionally, ice constricts blood vessels, reducing the speed at which the venom travels to other parts of the body.

The Portuguese Man O' War is often confused with a jellyfish, which is incorrect and may lead to improper treatment of stings, as the venom is different. A second sting may lead to an allergic reaction.

Predators

The Loggerhead Turtle, which is apparently immune to Man O' War toxins, is commonly seen feeding on the Man O' War.^[3]

The sea slug Glaucus atlanticus also feeds on the Man O' War.

Etymology

The Portuguese Man O' War (named caravela-portuguesa in Portuguese) is named for its air bladder, which looks similar to the sails of the Portuguese fighting ship (Man of war) Caravela redonda (an armed 4-sail caravel), of the 14th and 15th centuries.

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