Portuguese man o' war facts for kids
Quick facts for kids Portuguese man o' war |
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Physaliidae
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| Physalia physalis (Linnaeus, 1758)
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The Portuguese man o' war (Physalia physalis) is a Cnidarian invertebrate. It lives in the sea. It is sometimes called the blue bubble, or man-of-war. Its common name comes from a Portuguese war ship of the 15th and 16th century. The ship had triangular sails, similar in shape to the bladder of the man o' war.
The Portuguese Man o' War has a reputation for swarming in groups of thousands. It is also known for its powerful sting.
Contents
Structure
Physalia is not a single animal: it is a siphonophore. This is a colony of four kinds of zooids. Zooids are very small, highly modified individuals. These zooids are specialized polyps and medusoids. Though structurally similar to other cnidarians, the zooids do not live by themselves: they are attached to each other. Each type of zooid does not have some structure and functions. It depends for survival on the others doing what it cannot do by itself.
A similar group of animals are the chondrophores. They are specialized hydroids, which also float at the surface of the open ocean.
Description
The pneumatophore, or bladder, is the most conspicuous part of the man o' war. It is translucent and tinged blue, purple, pink, or mauve, and may be 9 to 30 cm (3.5 to 11.8 in) long and rise as high as 15 cm (6 in) above the water. The pneumatophore functions as both a flotation device and a sail for the colony, allowing the colony to move with the prevailing wind. The gas in the pneumatophore is part carbon monoxide (0.5–13%), which is actively produced by the animal, and part atmospheric gases (nitrogen, oxygen and noble gases) that diffuse in from the surrounding air. In the event of a surface attack, the pneumatophore can be deflated, allowing the colony to temporarily submerge.
The colony hunts and feeds through the cooperation of two types of zooid: gastrozooids and tentacle-bearing zooids known as dactylozooids or tentacular palpons. The dactylozooids are equipped with tentacles, which are typically about 10 m (30 ft) in length but can reach over 30 m (100 ft). Each tentacle bears tiny, coiled, thread-like structures called nematocysts. Nematocysts trigger and inject venom on contact, stinging, paralyzing, and killing adult or larval squids and fishes.
Distribution
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Portuguese man o' war washed up on a beach
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They are often found ashore in large groups
Found mostly in tropical and subtropical waters, 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. Portuguese man-o-war have no means of propulsion, and move passively, driven by the winds, currents, and tides.
Winds can drive them into bays or onto beaches. Often, finding a single Portuguese man o' war is followed by finding many others in the vicinity. The Portuguese man o' war is well known to beachgoers for the painful stings delivered by its tentacles. Because they can sting while beached, the discovery of a man o' war washed up on a beach may lead to the closure of the beach.
Left- and right-handedness
For each man o' war or bluebottle, the float can be oriented towards the left or the right (dimorphism), believed to be an adaptation that prevents the entire population from being washed on shore to die. The "left-handed" bluebottles sail to the right of the wind, while the "right-handed" bluebottles sail to the left. The wind will always push the two types of bluebottles in different directions, so at most half the population will be pushed towards the coast. Regional populations of Portuguese man o' war can have substantial differences in float size and the number of long tentacles used for hunting. The regional form previously known as P. utriculus, the bluebottle, has a float rarely exceeding 10 cm in length and has one long hunting tentacle that is less than 3 m long. In comparison, the typical man o' war has a float of around 15 cm, reported up to 30 cm, and several hunting tentacles that can reach 30 m in mature colonies when fully extended.
Predators and prey
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Blue dragon, Glaucus atlanticus
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Violet snail, Janthina janthina
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The Portuguese man o' war is a carnivore. Using its venomous tentacles, a man o' war traps and paralyzes its prey while "reeling" it inwards to the digestive polyps. It typically feeds on small adult fish and fish fry (young fish), and sometimes zooplankton, shrimp and other small crustaceans.
The organism has few predators of its own; one example is the loggerhead turtle, which feeds on the Portuguese man o' war as a common part of its diet. The turtle's skin, including that of its tongue and throat, is too thick for the stings to penetrate. Also, the blue sea slug Glaucus atlanticus specializes in feeding on the Portuguese man o' war, as does the violet snail Janthina janthina. The ocean sunfish's diet, once thought to consist mainly of jellyfish, has been found to include many species, the Portuguese man o' war being one such example.
The blanket octopus is immune to the venom of the Portuguese man o' war; young individuals have been observed to carry broken man o' war tentacles, which males and immature females rip off and use for offensive and defensive purposes.
The man-of-war fish, Nomeus gronovii, is a driftfish native to the Atlantic, Pacific and Indian Oceans. It is notable for its ability to live within the deadly tentacles of the Portuguese man o' war, upon whose tentacles and gonads it feeds. Rather than using mucus to prevent nematocysts from firing, as is seen in some of the clownfish sheltering among sea anemones, the fish appears to use highly agile swimming to physically avoid tentacles. The fish has a very high number of vertebrae (41), which may add to its agility and primarily uses its pectoral fins for swimming—a feature of fish that specialize in maneuvering tight spaces. It also has a complex skin design and at least one antibody to the man o' war's toxins. Although the fish seems to be 10 times more resistant to the toxin than other fish, it can be stung by the dactylozooides (large tentacles), which it actively avoids. The smaller gonozooids do not seem to sting the fish and the fish is reported to frequently "nibble" on these tentacles.
Commensalism and symbiosis
The Portuguese man o' war is often found with a variety of other marine fish, including yellow jack. 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 eat.
Life cycle
Man o' war individuals are either male or female. Mating takes place primarily in the autumn, when eggs and sperm are shed from gonophores into the water.
A fertilized man o' war egg develops into a larva that buds off new zooids as it grows, gradually forming a new colony. This development initially occurs under the water, and has been reconstructed by comparing different stages of larvae collected at sea. The first two structures to emerge are the pneumatophore (sail) and a single, early feeding zooid called a protozooid; later, gastrozooids and tentacle-bearing zooids are added. Eventually, the growing pneumatophore becomes buoyant enough to carry the immature colony on the surface of the water.
Venom
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 those of the live organism in the water and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.
Stings usually cause severe pain to humans, leaving whip-like red welts on the skin that normally last two or three days after the initial sting. The pain normally subsides after about one to three hours (depending on the victim's biology). However, the venom can travel to the lymph nodes and may cause symptoms that mimic an allergic reaction, including swelling of the larynx, airway blockage, cardiac distress and an inability to breathe. Other symptoms may include fever and shock and, in some extreme cases, even death, although this is extremely rare. Medical attention for those exposed to large numbers of tentacles may become necessary to relieve pain or open airways if the pain becomes excruciating or lasts for more than three hours, or if breathing becomes difficult. Instances in which the stings completely surround the trunk of a young child are among those that may be fatal.
The species 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.
Treatment of stings
Stings from a Portuguese man o' war can result in severe dermatitis characterized by long, thin, open wounds that resemble those caused by a whip. These are not caused by any impact or cutting action, but by irritating urticariogenic substances in the tentacles.
Images for kids
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Man o' war warning sign, Hawaii
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Portuguese man o' war, Miami Beach, Florida, March 2008
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Portuguese man o' war, Palm Beach, Florida, May 2013
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The name comes from a resemblance of the animal to a sailing warship, the Portuguese man-of-war (the caravel circa 1500) -
Illustration of Physalia physalis, 1807
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Anatomy of a Physalia physalis colony with descriptions of the function of each zooid
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Looking down from above a man o' war, showing its sail. Sails can be left-handed or right-handed.
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The bluebottle course at zero angle of attack is dependent on the sail camber
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See also
In Spanish: Carabela portuguesa para niños
