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hydra
hydra , common name for freshwater organisms in the phylum Cnidaria, which includes jellyfish, sea anemones, and corals. Hydras are widely distributed in lakes, ponds, and sluggish streams. They are small, cylindrical, solitary organisms, the largest reaching about 1 in. (2.5 cm) in length. They attach themselves temporarily to water plants or submerged objects, using an adhesive pedal disk at the anal end. The simple body consists of an outer layer of epidermis, a middle noncellular layer of mesoglea, and an inner layer of gastrodermis lining the simple gastrovascular cavity, where the final stages of food digestion occur. A whorl of tentacles surrounds the mouth. Hydras feed on small plankton organisms, especially microcrustaceans, stunning them with stinging cells (nematocysts) in the tentacles. Hydras reproduce asexually by budding and sexually by means of gonadal cells formed on the sides of the body. The green hydra, Chlorhydra viridissima, contains green algae living symbiotically in its gastrodermal cells. The gray and brown hydras belong to the genus Pelmatohydra. Several species of hydra also occur in American waters. Hydras are classified in the phylum Cnidaria , class Hydrazoa. |
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"hydra." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "hydra." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-hydra.html "hydra." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-hydra.html |
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hydra
hy·dra / ˈhīdrə/ • n. a minute freshwater coelenterate with a stalklike tubular body and a ring of tentacles around the mouth. • Genus Hydra, class Hydrozoa. |
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"hydra." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "hydra." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O999-hydra005.html "hydra." The Oxford Pocket Dictionary of Current English. 2009. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-hydra005.html |
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hydra
hydra Popular name for a group of small, freshwater organisms including the jellyfish, coral and sea anemone.
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"hydra." World Encyclopedia. 2005. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "hydra." World Encyclopedia. 2005. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O142-hydra.html "hydra." World Encyclopedia. 2005. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-hydra.html |
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Hydra
Hydra Greece: see Ídhra . |
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"Hydra." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "Hydra." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-X-Hydra.html "Hydra." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-X-Hydra.html |
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Hydra
Hydra See HYDROIDA.
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MICHAEL ALLABY. "Hydra." A Dictionary of Zoology. 1999. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "Hydra." A Dictionary of Zoology. 1999. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O8-Hydra.html MICHAEL ALLABY. "Hydra." A Dictionary of Zoology. 1999. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-Hydra.html |
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Hydra
Hydra
•airer, bearer, carer, Clara, darer, declarer, Demerara, Éire, habanera, Halmahera, parer, Perak, primavera, repairer, Rivera, Riviera, Sarah, scarer, sharer, snarer, sparer, squarer, starer, swearer, tearer, wearer
•cause célèbre • torch-bearer
•swordbearer • pallbearer • wayfarer
•seafarer • capoeira • Phaedra
•sacra, simulacra
•Libra, vers libre
•ex cathedra
•chypre, Ypres
•palaestra (US palestra) • urethra
•joie de vivre
•mirror, sirrah
•Coimbra • Middlesbrough • Indra
•Sintra
•aspidistra, sistra
•algebra • orchestra • vertebra
•Beira, Fujairah, Hegira, Lyra, Myra, naira, palmyra, spirogyra
•Hydra • Lycra
•begorra, Gomorrah, horror
•double entendre • genre • amour propre • Le Nôtre • contra
•Cosa Nostra, rostra
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"Hydra." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "Hydra." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O233-Hydra.html "Hydra." Oxford Dictionary of Rhymes. 2007. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O233-Hydra.html |
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