Coral

see Anthozoa

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Corals are gastrovascular marine cnidarians (phylum Cnidaria; class Anthozoa) existing as small sea anemone-like polyps, typically forming colonies of many individuals. The group includes the important reef builders known as hermatypic corals, found in tropical oceans, and belonging to the subclass Zoantharia of order Scleractinia (formerly Madreporaria). The latter are also known as stony corals in as much as the living tissue thinly covers a skeleton composed of calcium carbonate. A large scale coral is actually formed of many individual polyps, up to a few millimetres in diameter, which are individual organisms. However they function as one organism by sharing nutrients via channels in the skeleton and are clones of each other, hence having the same DNA.

Related Topics:
Gastrovascular - Cnidaria - Anthozoa - Sea anemone - Polyp - Reef - Hermatypic coral - Ocean - Zoantharia - Scleractinia - Calcium carbonate - Polyps - Organism

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The hermatypic corals obtain much of their nutrient requirement from symbiotic unicellular algae called zooxanthellae, and so are dependent upon growing in sunlight. As a result, these corals are usually found not far beneath the surface, although in clear waters corals can grow at depths of 60 m (200 ft). Corals breed by spawning, with many corals of the same species in a region releasing gametes simultaneously over a period of one to several nights around a full moon.

Related Topics:
Symbiotic - Alga - Zooxanthella - Gamete - Moon

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Corals are major contributors to the physical structure of coral reefs that develop only in tropical and subtropical waters. Isolated corals exist even in cold waters, such as off the coast of Norway. The most extensive development of extant coral reef is the Great Barrier Reef off the coast of Queensland, Australia. Indonesia is home to 581 of the world's 793 known coral reef-building coral species.

Related Topics:
Coral reef - Norway - Great Barrier Reef - Queensland - Australia - Indonesia

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