| Portuguese man o' war | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hydrozoa |
| Order: | Siphonophora |
| Family: | Physaliidae |
| Genus: | Physalia |
| Species: | P. physalis |
| Binomial name | |
| Physalia physalis (Linnaeus, 1758) |
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The Portuguese man o' war (Physalia physalis), also known as the Portuguese man-of-war, man-of-war, or bluebottle, is a jelly-like marine invertebrate of the family Physaliidae. Its venomous tentacles can deliver a powerful sting. The name "man o' war" is taken from the man-of-war, a 16th century English armed sailing ship that was based on an earlier Portuguese vessel.
Despite its outward appearance, the man o' war is not a true jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single creature, but a colonial organism made up of many minute individuals called zooids.[1] 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.
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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.[2] 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.[3]
In the Mediterranean Sea, the man o' war was first spotted off the coast of Spain, and then later in Corsica.[4][5] In 2010, the man o' war was sighted around Malta in the Mediterranean.[6] In the summer of 2009, Pembrokeshire County Council warned bathers in its waters that the organisms had been sighted in Welsh waters. In Ireland, there were dozens of confirmed sightings (in 2009–2010), from Termonfeckin in County Louth to the coast of County Antrim [7] On the other side of the Atlantic, they wash ashore along the northern Gulf of Mexico and east and west coasts of Florida. An abundance of Portuguese men o' war can be found in the waters of Costa Rica, especially in March and April, while they are also found off of Guyana. They wash up on the shore during certain months of the year. They are reported abundantly in the waters near Karachi, Pakistan in the summer months, and are also common in the ocean off parts of Australia, where they are known more commonly as 'blue-bottles', and New Zealand. During these months, they come ashore in the Gulf of California after rain, where they are known as agua(s) mala(s) by locals. They are also frequently found along the east coast of South Africa, particularly during winter storms if the wind has been blowing steadily on-shore for several hours, as well as around the Hawaiian Islands.
Strong onshore winds may drive them into bays or onto beaches. It is rare for only a single Portuguese man o' war to be found; the discovery of one usually indicates the presence of many, as they are usually congregated by currents and winds into groups of thousands.[2] 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 might lead to the closure of the whole beach.[8]
The Portuguese man o' war is composed of four types of polyp.[2] One of the polyps, a gas-filled bladder called the pneumatophore (commonly known as the marissa or 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 (4 to 12 in) long and may extend as much as 15 centimetres (6 in) above the water. The gas that the Portuguese man o' war secretes into its sail has approximately the same composition as the atmosphere, but may build up a high concentration of carbon dioxide (up to 90%). The sail is equipped with a siphon. To escape a surface attack, the sail can be deflated, allowing the man o' war to briefly submerge.[9]
The other three polyp types are known as dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding) [10] These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 metres (30 ft) in length but can be up to 50 metres (165 ft).[2] 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 creatures 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. 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.[11]
The stinging, venom-filled nematocysts[12] 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 creature in the water and may remain potent for hours or even days after the death of the creature or the detachment of the tentacle.[13]
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,[14] 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.
The best treatment for a Portuguese man o' war sting is:
Vinegar is not recommended for treating stings.[16] 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.[19]
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.
The Portuguese man o' war is a carnivore.[2] 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 loggerhead turtle feeds on the Portuguese man o' war, a common part of the loggerhead's diet.[20] 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,[21] as does the violet snail Janthina janthina.[22]
The blanket octopus is immune to the venom of the Portuguese man o' war and has been known to rip off the man o' war's tentacles and use them for defensive purposes.[23]
The ocean sunfish's primary diet consists of jellyfish, but it can also consume Portuguese men o' war.
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.[24]
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