Portuguese Man-o-War

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Adam Walker felt the painful stings of man o war towards the end of his Molokai Channel crossing in Hawaii

noun - Portuguese man o war is a jelly-like floating marine invertebrate found in warm water seas and oceans around the world that is a colonial organism made up of many minute individuals called zooids and is dependent on winds, currents and tides for its movement. It is most common in the tropical and subtropical regions of the Pacific and Indian Oceans, but can drift outside of this range on warm currents such as the Atlantic Gulf Stream.

The Portuguese man o war (Physalia physalis) is a jelly-like marine invertebrate of the family Physaliidae. The name "man-of-war" is borrowed from the man-of-war, a 16th century English armed sailing ship which was based on an earlier Portuguese vessel.

Despite its outward appearance, the man o war is not a true jellyfish but a siphonophore, which differ from jellyfish in that they are not actually a single creature, 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, are attached to each other and physiologically integrated to the extent that they are incapable of independent survival.

The man o war is found in warm water seas floating on the surface of open ocean, its air bladder keeping it afloat and acting as a sail while the rest of the organism hangs below the surface. It has no means of self-propulsion and is entirely dependent on winds, currents, and tides. It is most common in the tropical and subtropical regions of the Pacific and Indian oceans, but can drift outside of this range on warm currents such as the Atlantic Gulf Stream.

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 they can be found anywhere in the open ocean (especially warm water seas), they are most commonly found in the tropical and subtropical regions of the Pacific and Indian oceans, and the northern Atlantic Gulf Stream. The Man o' War has been found as far north as the Bay of Fundy and the Hebrides.

In the Mediterranean Sea, the man o war was first spotted off the coast of Spain, and then later in Corsica. In 2010, sightings of the man o war were recorded around Malta in the Mediterranean. 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 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 Man o' Wars 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. Man o war typically travel in groups of 1,000 or more individuals.

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 a number of men o' war washed up on a beach might 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 marissa or sail), enables the organism to float. This sail is translucent and tinged blue, purple, pink or mauve. The sail may be 4 to 12 inches (9 to 30 centimeters) long and may extend as much as 6 inches (15 centimeters) above the water. The gas which 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 must stay wet to ensure survival and occasionally they may roll slightly to wet the surface of the sail. To escape a surface attack, the sail can be deflated allowing the man o war to briefly submerge.

The other three polyps are known as: dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding). These polyps are "clustered." The dactylzooids make up the tentacles that can be up to 50 meters or 165 feet in length, but are typically only 10 meters (30 feet). 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 work to drag prey into range of the digestive polyps, the gastrozooids, another type of polyp that surround and digest the food by secreting enzymes that break down proteins, carbohydrates and fats. Gonozooids are responsible for reproduction.

A small fish, Nomeus gronovii, are nearly immune to the poison from the stinging cells, and can live among the tentacles. They have a commensal symbiotic relationship, i.e. a relationship beneficial for the symbiont, with no negative or pathogenic effect on the host. The tiny fish often "snack" upon the tendrils as well, changing the nature of the relationship to parasitic.

The Portuguese man o war's float is bilaterally symmetrical with the tentacles at one end, whereas by contrast the chondrophores are radially symmetrical with the sail at an angle or in the center. Also, the Portuguese Man o' War has a siphon, while the chondrophores do not.


The Portuguese man o war is 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 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.

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 where pain persists or is intense, if 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 if either area becomes red, warm and tender.

Research suggests that in the normal course 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 creature 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).[15][16] Follow up with the application of hot water (45 °C/113 °F) to the affected area, which eases the pain of a sting by denaturing the toxins.

If eyes have been affected they should be irrigated 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 are light sensitive after irrigating, or there is any concern, a doctor should be seen 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 P. physalis, the larger man o war 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 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, and they have been known to rip off its tentacles and use them for defensive purposes.

The Ocean Sunfish's primary diet consists of jellyfish, but it can also consume Portuguese man o war. Because of the Ocean Sunfish's size and bulk, it must consume large amounts of these animals to compensate for their low nutritional value.

The Portuguese man o war is classified as a carnivore. Using its venomous tentacles, the man o war traps and paralyze its prey. Typically, Man o' War feed upon small aquatic organisms, such as fish and plankton.

Commensalism and symbiosis

The Portuguese man o war is often found with a variety of marine fish, including shepherd fish, clownfish and yellow jack, species that are rarely found elsewhere. The clownfish can swim among the tentacles with impunity, possibly due to its mucus that does not trigger the nematocysts. The shepherd fish seems to avoid the larger, stinging tentacles, but feeds on the smaller tentacles beneath the gas bladder. 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.


The swimmer was stung unmercifully by the Portuguese man o war.



Portuguese man-of-war, man-of-war, man 'o war, Blue bottle, Jellyfish, blue bottle jellyfish

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