Portuguese man o' war

This article is about the marine invertebrate. For other uses, see Man o' war.

Portuguese man o' war
Scientific classification
Kingdom:	Animalia
Phylum:	Cnidaria
Class:	Hydrozoa
Order:	Siphonophora
Family:	Physaliidae
Genus:	Physalia
Species:	P. physalis
Binomial name
Physalia physalis (Linnaeus, 1758)

The Atlantic Portuguese man o' war (Physalia physalis), also known as the Man-of-war, bluebottle, or floating terror, is a marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting. Despite its outward appearance, the Portuguese man o' war is not a common jellyfish but a siphonophore, which is not actually a single multicellular organism, but a colony of specialized minute individuals called zooids. These zooids are attached to one another and physiologically integrated to the extent that not only are they incapable of independent survival, they also have to work together to function as a single organism.

Etymology

The name "man o' war" comes from the man-of-war, an 18th-century armed sailing ship, and the cnidarian's supposed resemblance to the Portuguese version at full sail. In other languages it is simply known as the 'Portuguese war-ship' (Dutch: portugees oorlogsschip, Swedish: portugisisk örlogsman, Norwegian: portugisisk krigsskip, Finnish: portugalinsotalaiva), the 'Portuguese galley' (German: portugiesische Galeere, Hungarian: portugál gálya), the 'Portuguese caravel' (Portuguese: caravela portuguesa, Spanish: carabela portuguesa, Italian: caravella portoghesecode: it is deprecated ), or the 'Portuguese little boat' (Russian: португальский кораблик).

Habitat

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. Since the Portuguese man o' war has no means of propulsion, it is moved by a combination of 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 and the Hebrides.

Strong winds may drive them into bays or onto beaches. Often the finding of a single Portuguese man o' war results in the finding of many others in the vicinity. They must be treated with caution, and the discovery of a man o' war washed up on a beach may lead to the closure of the whole beach.

Structure

Physalia physalis

The Portuguese man o' war is composed of three types of polyps and an associated gas-filled air sac called a pneumatophore or "sail". The pneumatophore should probably not be considered a polyp as it 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 generates carbon monoxide in its gas gland, filling 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 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 organism to briefly 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 be up to 50 m (160 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. 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.

Venom

This species and the smaller Indo-Pacific man o' war (Physalia utriculus) are 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.

The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o' war can paralyze small fish and other prey. Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.

Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that normally last two or three days after the initial sting, though the pain should subside after about 1 to 3 hours (depending on person). However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, a more intense pain. Venom effects may mimic an allergic reaction but this is not due to true allergy which is defined by serum IgE. There can also be serious effects, including fever, shock, and interference with heart and lung function. Stings may also cause death, although this is extremely rare. Medical attention may be necessary, especially if pain persists or is intense, the reaction is extreme, the rash worsens, a feeling of overall illness develops, a red streak develops between swollen lymph nodes and the sting, or either area becomes red, warm, and tender.

Treatment of stings

Stings from the Portuguese man o' war may result in severe dermatitis, characterized by extremely painful, long, thin open wounds that resemble those caused by a whip, but are not caused by any impact or cutting action, but rather irritating urticariogenic substances in the tentacles. Treatment for a Portuguese man o' war sting includes the application of salt water and hot water to the affected area.

Vinegar has been shown to inactivate undischarged cnidae on tentacles. Vinegar has also been shown to inactivate venom. Still there exists contention in the literature in that other isolated studies suggest that vinegar dousing increases toxin delivery and worsens symptoms of stings from the nematocysts of this species. Vinegar has also been claimed to provoke hemorrhaging when used on the less severe stings of cnidocytes of smaller species.

Predators and prey

The Portuguese man o' war is a carnivore. Using its venomous tentacles, a man o' war traps and paralyzes its prey. It typically feeds on small marine organisms, such as fish and plankton.

Portuguese man o' war in Tayrona National Park, Colombia

The loggerhead turtle feeds on the Portuguese man o' war, a common part of the loggerhead's diet. The turtle's skin is too thick for the sting to penetrate.

The sea slug Glaucus atlanticus also feeds on the Portuguese man o' war, as does the violet snail Janthina janthina.

The blanket octopus is immune to the venom of the Portuguese man o' war; young individuals carry broken man o' war tentacles, presumably for offensive and/or defensive purposes.

The ocean sunfish's primary diet consists of jellyfish, but it can also consume Portuguese man o' war.

Commensalism and symbiosis

A small fish, Nomeus gronovii (the man-of-war fish or shepherd fish), is partially immune to the venom from the stinging cells and can live among the tentacles. It seems to avoid the larger, stinging tentacles but feeds on the smaller tentacles beneath the gas bladder. The Portuguese man o' war is often found with a variety of other marine fish, including clownfish and yellow jack. The clownfish can swim among the tentacles with impunity, possibly owing to their mucus, which does not trigger the nematocysts.

All of these fish benefit from the shelter from predators provided by the stinging tentacles, and for the Portuguese man o' war the presence of these species may attract other fish on which to feed.

Gallery

• Portuguese Man O' War Miami March 2008.jpg

  Portuguese man o' war in Miami, Florida

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  Portuguese men o' war washed ashore on Maroubra Beach

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  Portuguese man o' war captured live in Mayaro Beach, Trinidad and Tobago

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  Portuguese man o' war at Palm Beach, Florida

See also

• Chondrophores (porpitids), a different hydrozoan colonial organism

External links

• Siphonophores.org General information on siphonophores, including the Portuguese man-of-war
• National Geographic: Portuguese Man-of-War
• Life In The Fast Lane: Blue bottle
• Contact: Myrtle Beach, South Carolina