Portuguese-Man-o'-War

The Portuguese Man o’ War, also known as the Bluebottle, is a jellyfish-like marine invertebrate of the family Physaliidae. Despite its outward appearance, the Man o’ War is not a jellyfish, but a siphonophore. Siphonophorae differ from jellyfish in that they are not actually single creatures, but colonial organisms 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.

Mollusks and zoophytes.

The term ‘zoophyte’ used to be given to animals that resemble plants, however, it is no longer used in relation to scientific classification. In the drawing you see four siphonophores belonging to genera Physalia, Rhizophysa, Stephanomia and Physophora in the order Siphonophorae. Siphonophores often resemble jellyfishes, however they are actually colonies of multicellular zoa (singular zooid), which are connected via tissues and preform highly specialised functions. At the very top of the drawing is a gorgeous nudibranch, called Glaucus; its name comes from a sea-god in ancient Greek mythology. 

This drawing is from Voyage de découvertes aux terres australes by François Péron

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The Portuguese Man o’ War are responsible for up to 10,000 human stings in Australia each summer. The stinging, venom-filled nematocysts in the tentacles of the 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 detachment of the tentacle.

Stings usually cause severe pain to humans, leaving whip-like, red welts on the skin that typically last 2 or 3 days after the initial sting, though the pain should subside after an hour. However, the venom can travel to the lymph nodes and may cause, depending on the amount of venom, a more intense pain. Stings may also cause death, although this is extremely rare. 

The Portuguese Man O’ War (Physalia physalis), also known as the Portuguese Man-Of-War, Man-Of-War, or Bluebottle, is a jellyfish-like marine cnidarian of the family Physaliidae. Its venomous tentacles can deliver a powerful sting. 
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 
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 centimeters (4 to 12 in) long and may extend as much as 15 centimetres (6 in) above the water. 
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 (30 ft) in length but can be up to 50 metres (165 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. 
The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o’ war can paralyze small fish and other prey. 
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. 
The imperial blackfish S. ovalis is a subtropical species with a 
wide geographic distribution reported from the eastern Atlantic, western central Atlantic, and the Mediterranean
Young are epipelagic and associate with floating jellyfish, including Physalia. (via)

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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.

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.