Portuguese Man-of-War:

A jellyfish or not?

Most of you must have heard of a particular group of marine creature known as jellyfish. Some of you may have even had nasty experiences by coming into contact with certain species of jellyfish on the beach which are said to be harmful,Today we like to introduce you to a marine species, an invertebrate called the Portuguese Man-of War (Physalia physalis) that is considered to be very venomous, and many mistake them for jellyfish.

What is interesting is that the Portuguese Man-of-War not only isn't a jellyfish but is also not a single entity. So, the Portuguese Man-of-War is not even an "it," but a "they" and is called a siphonophore, an animal made up of a colony of organisms working together.The siphonophore, differ from jellyfish as 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-specialised 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 Portuguese Man-of-War are composed of four types of polyp.These polyps are "clustered".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. Sometimes these animals are also called bluebottles for the purplish blue colour of their pneumatophores.

The sail 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 which the Portuguese Man of 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 90per cent).

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-of-War to briefly submerge.

The other three polyps are known as: dactylozooid (defence), gonozooid (reproduction), and gastrozooid (feeding). They make up the tentacles that are typically 10 metres (30 ft) in length but can be up to 50 metres (165 ft).

The Portuguese Man-of-War tentacles are made up of threa ployps is classified as a carnivorous species uses venomous tentacles to trap and paralyse the prey that consists mostly of small crustaceans, small fish, algae and other members of the surface plankton. In general it has been observed that the creatures eat

The bladder is above the water.

Floating in the sea.

basically anything that comes in contact with the stinging tentacle polyps,the dactylozooids. 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 the range of the digestive polyps, the gastrozooids, another type of polyp that surround and digest the food.Muscles in each tentacle contract and drag prey into range of the digestive polyps, the gastrozooids, which, acting like small mouths, consume and digest the food by phagocytosis - by secreting a full range of enzymes that variously break down proteins, carbohydrates and fats. Gonozooids are responsible for reproduction.

Why is this creature known as the Portuguese Man-of-War?According to scientists the name comes from the uppermost polyp, the gas-filled bladder, ( pneumatophore), which sits above the water that resembles an old warship at full sail. The gas-filled bladder, remains at the surface, while the remainder is submerged. Sometimes these animals are also called bluebottles for the purplish blue colour of their pneumatophores. The tentacles, the creature's second organism are long, thin tendrils that can extend up to 165 feet (50 metres) in length below the surface, although 30 feet (10 metres) is more the average.

The species of Portuguese Man-of War is often found with a variety of marine fish, including shepherd fish, clownfish and yellow jack, species that are rarely found elsewhere. Man-of-War are found, sometimes in groups of 1,000 or more, floating in warm waters throughout the world's oceans. They have no independent means of propulsion and either drift on the currents or catch the wind with their pneumatophores. Do you know that they have the ability to deflate their air bags and briefly submerge to avoid threats on the surface?

The Man - of - War are found in warm water seas floating on the surface of open ocean, with the air bladder keeping them afloat and acting as a sail while the rest of the organism hangs below the surface. They are 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.

An abundance of them 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. 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.

[Fast facts]

* The tiny Nomeus gronovii fish is immune to the sting of the Portuguese Man-of-War. It lives among the tentacles and even snacks on the stinging tendrils.

* The species is a jelly-like marine invertebrate of the family Physaliidae.

* The name " Man-of-War" is taken from the man-of-war, a 16th century English armed sailing ship which was based on an earlier Portuguese vessel.

* The Man-of-War comprises four separate polyps.

* The Man-of -War have no means of propulsion and move by a combination of winds, currents, and tides. They move by means of their crests,that functions as a sail.

* The stinging tentacles (nematocysts) can cause extremely painful stings, shock, and in certain instances, death.Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live creatures in the water, and may remain potent for hours or even days after the death of the creatures or the detachment of the tentacle.

* For humans, a Man-of-War sting is excruciatingly painful, but rarely deadly. But beware-even dead ones washed up on shore can deliver a sting.

* They are carnivorous species and the muscles in the tentacles draw prey up to a polyp containing the gastrozooids or digestive organisms.

Facts and pix: Internet