sea anemone

sea anemone
any sedentary marine animal of the phylum Coelenterata, having a columnar body and one or more circles of tentacles surrounding the mouth.

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Any of more than 1,000 cnidarian species in the order Actiniaria, found from the tidal zone of all oceans to depths of more than 30,000 ft (10,000 m) and occasionally in brackish water.

Species vary from less than 1 in. (3 cm) to about 5 ft (1.5 m) in diameter. The mouth, at the upper end of the cylindrical body, is surrounded by petal-like, usually colourful tentacles that bear stinging nematocysts for paralyzing prey such as fishes. Some species eat only microorganisms. Most species remain permanently attached to a hard surface such as a rock or the back of a crab.

Sea anemone, Tealia

(Top) M. Woodbridge Williams; (bottom) George Lower
The National Audubon Society Collection/Photo Researchers

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 any member of the invertebrate order Actiniaria (class Anthozoa, phylum Cnidaria), soft-bodied, primarily sedentary marine animals resembling flowers. They are found from the tidal zone of all oceans to depths of more than 10,000 metres (about 33,000 feet). Some live in brackish water. They are largest, most numerous, and most colourful in warmer seas. The colourful Tealia are found in temperate regions.

      The nearly 1,000 species vary in size from a few millimetres (a fraction of an inch) in diameter and length to about 1.5 metres (about 5 feet) in diameter. The largest sea anemones—also the largest cnidarians—are of the genus Stoichactis.

      Actinarians exhibit great variety in shape and habit. The cylindrical body may be thick and short or long and slender. The oral disk, containing the mouth, at the upper end of the body is surrounded by petal-like tentacles, which are often present in multiples of six. Sea anemones are commonly yellow, green, or blue; they are typically attached by the pedal disk, or base, to a hard surface such as a rock, wharf timber, a seashell, or the back of a crab. Most seldom move; some occasionally creep very slowly or move in a slow somersaulting fashion. Members of certain genera (e.g., Edwardsia, Halcampa, Peachia) have no pedal disk but burrow deep into the sand or mud, exposing only the mouth and tentacles. Members of the genus Minyas float near the ocean surface, with the mouth hanging downward.

      Sea anemones have no solid skeleton but may secrete a horny covering. Some species have adhesive-secreting structures and cover themselves with grains of sand, bits of shell, or other foreign objects.

      Nematocysts, microscopic stinging structures in the tentacles, are used to capture and paralyze prey such as fishes and other marine animals. Some species eat only microorganisms. Anemones are eaten by sea slugs, certain starfishes, eels, flounders, and codfish.

      In most species the sexes are separate. Sperm and eggs are usually discharged into the water, where fertilization occurs. Sometimes, as in Halcampa and Actinia, sperm are drawn into the female's gastrovascular cavity, in which the eggs are fertilized. Fertilized eggs develop, for example, into ciliated larvae that disperse to new areas before metamorphosing into adults. Reproduction sometimes occurs asexually by longitudinal fission (e.g., in Anemonia); that is, the animal splits lengthwise into two equal individuals. In some species (e.g., Metridium) the pedal disk breaks into fragments that grow into new individuals.

      Sea anemones often live in close association with other organisms. The hermit crab Pagurus arrosor carries a single anemone of the genus Calliactis on the snail shell it uses as a “house.” When the hermit crab grows too large for its shell, it moves to a new one, transplanting the anemone to the new shell. Similarly, the hermit crab Eupagurus prideauxi and the sea anemone Adamsia palliata are always found living together, never alone. Fishes of the genera Premnas and Amphiprion often live safely among the poisonous tentacles of an anemone such as a species of Stoichactis, Radianthus, or Discosoma. Such fish, however, may be stung and eaten by other anemone individuals, even of the same species.

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Universalium. 2010.

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Look at other dictionaries:

  • Sea anemone — Sea anemones Various examples of sea anemones Scientific classification …   Wikipedia

  • Sea anemone — Sea a*nem o*ne (Zo[ o]l.) Any one of numerous species of soft bodied Anthozoa, belonging to the order {Actinaria}; an actinian. [1913 Webster] Note: They have the oral disk surrounded by one or more circles of simple tapering tentacles, which are …   The Collaborative International Dictionary of English

  • sea anemone — n. any of an order (Actiniaria) of flowerlike, anthozoan sea polyps having a firm, gelatinous, often large, body without a skeleton, topped with petal like tentacles: they are often brightly colored and live attached to rocks, pilings, etc …   English World dictionary

  • sea anemone — ► NOUN ▪ a marine animal with a tube shaped body which bears a ring of stinging tentacles around the mouth …   English terms dictionary

  • sea anemone — noun marine polyps that resemble flowers but have oral rings of tentacles; differ from corals in forming no hard skeleton • Syn: ↑anemone • Hypernyms: ↑anthozoan, ↑actinozoan • Hyponyms: ↑actinia, ↑actinian, ↑ …   Useful english dictionary

  • sea anemone — UK / US noun [countable] Word forms sea anemone : singular sea anemone plural sea anemones a small brightly coloured sea animal that looks like a flower and fixes itself onto a rock …   English dictionary

  • sea anemone — sea a.nemone n a small brightly coloured sea animal that sticks onto rocks and looks like a flower …   Dictionary of contemporary English

  • sea anemone — sea a,nemone noun count a small brightly colored ocean animal that looks like a flower and fixes itself onto a rock …   Usage of the words and phrases in modern English

  • sea anemone — sea polyp with a gelatinous body and petal like tentacles …   English contemporary dictionary

  • sea anemone — sea′ anem one n. ivt any solitary, attached marine polyp of the order Actinaria, having a firm, gelatinous body topped with tentacles …   From formal English to slang

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