http://dn.sapo.pt/inicio/ciencia/interior.aspx?content_id=1216608&seccao=Biosfera
Portuguese Man o' War
The Portuguese Man o' War (Physalia physalis), also known as the blue bubble, blue bottle, man-of-war, or the Portuguese man o' war, is a jelly-like, marine invertebrate of the family: Physaliidae, order: Siphonophora, class: Hydrozoa, and Phylum: Cnidaria.
The common name comes from a Portuguese war ship type of the 15th and 16th century, the man-of-war (named caravela-portuguesa in Portuguese, caravel), which had triangular sails similar in outline to the bladder of the Portuguese Man O' War.
They are commonly but erroneously thought of and referred to as a jellyfish. In fact, a Portuguese Man O' War is not a single animal, but rather a siphonophore – a colony of four kinds of minute, highly modified individuals, which are specialized polyps and medusoids.[1] Each such zooid in these pelagic colonial hydroids or hydrozoans has a high degree of specialization and, although structurally similar to other solitary animals, are all attached to each other and physiologically integrated rather than living independently. Such zooids are specialised to such an extent that they lack the structures associated with other functions and are therefore dependent for survival on the others to do what the particular zooid cannot do by itself.
A similar group of animals are the chondrophores, which are specialised hydroids that float at the surface of the open ocean.
The Portuguese Man O' War is infamous for "swarming" in groups of thousands and for a very painful, powerful sting.
Habitat and locomotion
The Portuguese Man O' War lives at the surface of the ocean, with its float above the water, serving as a sail, and the rest of the organism hanging below the surface. It has no means of propulsion, but is moved by a combination of winds, currents, and tides. It is found in open ocean in all of the world's warm water seas but most commonly in the tropical and subtropical regions of the Pacific and Indian oceans, and the northern Atlantic Gulf Stream. Strong onshore winds may drive them into bays or on beaches.
Physalia physalis is the only widely distributed species. P. utriculus, commonly known as the bluebottle, frequently occurs in the Pacific and Indian oceans.
They are reported abundantly off the Karachi coast in Pakistan, and are common in the ocean off parts of Australia and New Zealand especially at the Sand's Pit and Hawkes Bay beaches during the months of June and July. They come ashore all along the northern Gulf of Mexico and both east and west coasts of Florida as well around the Hawaiian Islands. They are also frequently to be found along the east coast of South Africa, especially on the KwaZulu-Natal beaches (particularly if the wind has been blowing steadily on shore for a number of hours).
It is rare that only a single Portuguese Man O' War is found; the discovery of one usually indicates the presence of many as they can "swarm" in groups of thousands.
Attitudes to the presence of the Portuguese Man O' War vary around the world. Given their sting, they must be treated with caution and the discovery of a number of blue bottles washed up on the beach might lead to the closure of a whole beach.
Structure
The Portuguese Man O' War has an air bladder (known as the pneumatophore or sail) that allows it to float on the surface of the ocean. This sail is translucent and tinged blue, purple or mauve. The sail may be 9 to 30 centimetres long and may extend as much as 15 centimetres above the water. The Portuguese Man O' War secretes gas into its sail that is approximately the same in 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 every so often the Portuguese Man O' War 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 .
Below the main body dangle long tentacles, which occasionally reach 50 meters (165 ft) in length below the surface, although one metre (three feet) is the average. 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 surrounds and digest the food by secreting a full range of enzymes that variously break down proteins, carbohydrates and fats. Gonozooids are responsible for reproduction.
Certain small fish are able to live among the tentacles (being nearly immune to the poison from the stinging cells) and have a commensal symbiotic relationship, i.e. a relationship beneficial for the symbiont, with no negative or pathogenic effect on the host.
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.
http://en.wikipedia.org/wiki/Portuguese_Man_o'_War
