Coral
Coral
Pillar coral, Dendrogyra cylindricus
Scientific classification
Kingdom:
Animalia
Phylum:
Cnidaria
Class:
Anthozoa
Ehrenberg, 1831
Extant Subclasses and Orders
Alcyonaria
Alcyonacea
Helioporacea
Zoantharia
Antipatharia
Corallimorpharia
Scleractinia
Zoanthidea
[1][2] See Anthozoa for details
Corals are marine organisms from the class Anthozoa
and exist as small sea anemone–like polyps, typically in
colonies of many identical individuals. The group in-
cludes the important reef builders that are found in
tropical oceans, which secrete calcium carbonate to
form a hard skeleton.
A coral "head", commonly perceived to be a single
organism, is formed from thousands of individual but
genetically identical polyps, each polyp only a few milli-
meters in diameter. Over thousands of generations, the
polyps lay down a skeleton that is characteristic of their
species. A head of coral grows by asexual reproduction
of the individual polyps. Corals also breed sexually by
spawning, with corals of the same species releasing gam-
etes simultaneously over a period of one to several
nights around a full moon.
Although corals can catch small fish and animals
such as plankton using stinging cells on their tentacles,
these animals obtain most of their nutrients from photo-
synthetic unicellular algae called zooxanthellae. Con-
sequently, most corals depend on sunlight and grow in
clear and shallow water, typically at depths shallower
than 60 m (200 ft). These corals can be major contribut-
ors to the physical structure of the coral reefs that de-
velop in tropical and subtropical waters, such as the
enormous Great Barrier Reef off the coast of Queensland,
Australia. Other corals do not have associated algae and
can live in much deeper water, such as in the Atlantic or
Pacific, with the cold-water genus Lophelia surviving as
deep as 3000 m.[3] Examples of these can be found living
on the Darwin Mounds located north-west of Cape
Wrath, Scotland. Corals have also been found off the
coast of Washington State and the Aleutian Islan