Structure
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 centimetres (4 to 12 in) long and may extend as much as 15 centimetres (6 in) above the water. The gas that 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 is equipped with a siphon. In the event of a surface attack, the sail can be deflated, allowing the man o' war to briefly submerge.
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 creatures such as small fish and shrimp. Contractile cells in each tentacle drag the prey into range of the digestive polyps, the gastrozooids, which surround and digest the food by secreting enzymes that break down proteins, carbohydrates and fats. Gonozooids are responsible for reproduction.
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Famous quotes containing the word structure:
“The structure was designed by an old sea captain who believed that the world would end in a flood. He built a home in the traditional shape of the Ark, inverted, with the roof forming the hull of the proposed vessel. The builder expected that the deluge would cause the house to topple and then reverse itself, floating away on its roof until it should land on some new Ararat.”
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“I’m a Sunday School teacher, and I’ve always known that the structure of law is founded on the Christian ethic that you shall love the Lord your God and your neighbor as yourself—a very high and perfect standard. We all know the fallibility of man, and the contentions in society, as described by Reinhold Niebuhr and many others, don’t permit us to achieve perfection.”
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