Portuguese Man O' War

The Atlantic **Portuguese man o' war** (*Physalia physalis*), also known as the **man-of-war** or **floating terror**, is a marine hydrozoan of the family Physaliidae found in the Atlantic, Indian and Pacific Oceans. Its venomous long tentacles deliver a painful sting, which on extremely rare occasions has been fatal to humans. Despite its appearance, the Portuguese man o' war is not a true jellyfish but a siphonophore, which, unlike jellyfish, is not actually a single multicellular organism, but a colonial organism made up of specialized individual animals (of the same species) called zooids or polyps. These polyps are attached to one another and physiologically integrated, to the extent that they are unable to survive independently, and therefore have to work together and function like an individual animal.

The Indo-Pacific Portuguese man-of-war (*P. utriculus*), or blue bottle, is a related species with very similar appearance found throughout the Indian and Pacific Oceans.

## Description

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. As the Portuguese man o' war has no means of propulsion, it moves according to the winds, currents, and tides. Although it is most commonly found in the open ocean in tropical and subtropical regions, it has been found as far north as the Bay of Fundy, Cape Breton and the Hebrides.

Strong winds may drive them into bays or onto beaches. Often, finding a single Portuguese man o'war is followed by finding many others in the vicinity. They can sting while beached; the discovery of a man o' war washed up on a beach may lead to the closure of the beach.

Being a colonial siphonophore, the Portuguese man o' war is composed of three types of medusoids (gonophores, siphosomal nectophores, and vestigial siphosomal nectophores) and four types of polypoids (free gastrozooids, gastrozooids with tentacles, gonozooids, and gonopalpons), grouped into cormidia beneath the pneumatophore, a sail shaped structure filled with gas. The pneumatophore develops from the planula, unlike the other polyps. This sail is bilaterally symmetrical, with the tentacles at one end. It is translucent, and is tinged blue, purple, pink, or mauve. It may be 9 to 30 cm (3.5 to 11.8 in) long and may extend as much as 15 cm (5.9 in) above the water. The Portuguese man o' war fills its gas bladder with up to 14% carbon monoxide. The remainder is nitrogen, oxygen, and argon—atmospheric gases that diffuse into the gas bladder. Carbon dioxide also occurs at trace levels. The sail is equipped with a siphon. In the event of a surface attack, the sail can be deflated, allowing the colony to temporarily submerge.

The other three polyp types are known as dactylozooid (defense), gonozooid (reproduction), and gastrozooid (feeding). These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 m (33 ft) in length, but can reach over 30 m (98 ft). The long tentacles "fish" continuously through the water, and each tentacle bears stinging, venom-filled nematocysts (coiled, thread-like structures), which sting, paralyze, and kill adult or larval squids and fishes. Large groups of Portuguese man o' war, sometimes over 1,000 individuals, may deplete fisheries. Contractile cells in each tentacle drag the prey into range of the digestive polyps, the gastrozooids, which surround and digest the food by secreting enzymes that break down proteins, carbohydrates, and fats, while the gonozooids are responsible for reproduction.

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