Portuguese man o' war
|It has been suggested that Portuguese man-of-war dermatitis be merged into this article. (Discuss) Proposed since September 2013.|
The Portuguese man o' war (Physalia physalis), also known as the Portuguese man-of-war, Man-Of-War, or bluebottle, though often mistaken as a jellyfish, is a marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a painful sting.
Despite its outward appearance, the man o' war is not a jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single organism, but a colonial organism made up of many minute individuals called zooids. Each of these zooids is highly specialized, and, although structurally similar to other solitary animals, they are attached to one another and physiologically integrated to the extent that they are incapable of independent survival.
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), the 'Portuguese Galley' (German: Portugiesische Galeere, Hungarian: portugál gálya), or the 'Portuguese Caravel' (Portuguese: "Caravela Portuguesa", Italian: "Caravella portoghese", Swedish: "Portugisisk örlogsman").
Habitat and location
The 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 man o' war has no means of propulsion, it is moved by a combination of winds, currents, and tides. Although it can be found anywhere in the open ocean (especially warm water seas), it is most commonly found in the tropical and subtropical regions of the Pacific and Indian oceans and in the northern Atlantic Gulf Stream. The man o' war has been found as far north as the Bay of Fundy and the Hebrides.
Strong winds may drive them into bays or onto beaches. It is rare for only a single Portuguese man o' war to be found; often the finding of one results in the finding of many. Attitudes to the presence of the Portuguese man o' war vary around the world. Given their sting, however, they must always be treated with caution, and the discovery of men o' war washed up on a beach may lead to the closure of the whole beach.
The Portuguese man o' war is composed of four types of polyp. One of the polyps, a gas-filled bladder called the pneumatophore (commonly known as the sail), enables the organism to float. This sail is bilaterally symmetrical, with the tentacles at one end, and is translucent, tinged blue, purple, pink, or mauve. It may be 9 to 30 centimetres (3.5 to 12 in) long and may extend as much as 15 centimetres (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 man o' war to briefly submerge.
The other three polyp types are known as dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding). These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 metres (33 ft) in length but can be up to 50 metres (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.
This species and the smaller Indo-Pacific man o' war 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 2 or 3 days after the initial sting, though the pain should subside after about an hour. However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, a more intense pain. A sting may lead to an allergic reaction. 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, there is an extreme reaction, 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
The best treatment for a Portuguese man o' war sting is:
- To avoid any further contact with the Portuguese man o' war and to carefully remove any remnants of the organism from the skin (taking care not to touch them directly with fingers or any other part of the skin to avoid secondary stinging); then
- To apply salt water to the affected area (not fresh water, which tends to make the affected area worse)
- To follow up with the application of hot water (45 °C/113 °F) to the affected area from anywhere between 15-20 minutes  which eases the pain of a sting by denaturing the toxins.
- If eyes have been affected, to irrigate with copious amounts of room-temperature tap water for at least 15 minutes, and if vision blurs or the eyes continue to tear, hurt, swell, or show light sensitivity after irrigating, or there is any concern, to see a doctor as soon as possible.
Vinegar is not recommended for treating stings. Vinegar dousing increases toxin delivery and worsens symptoms of stings from the nematocysts of this species. Vinegar has also been confirmed to provoke hemorrhaging when used on the less severe stings of nematocysts of smaller species.
The Portuguese man o' war is often confused with jellyfish by its victims, which may lead to improper treatment of stings, as the venom differs from that of true jellyfish.
Predators and prey
The Portuguese man o' war is a carnivore. Using its venomous tentacles, a man o' war traps and paralyzes its prey. Typically, men o' war feed upon small aquatic organisms, such as fish and plankton.
The ocean sunfish's primary diet consists of jellyfish, but it can also consume Portuguese men o' war.
Commensalism and symbiosis
A small fish, Nomeus gronovii (the man o' war fish or shepherd fish), is partially immune to the poison 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 to feed on.
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