Coral

Coral
Temporal range: Cambrian – recent
Coral Outcrop Flynn Reef.jpg
A coral outcrop on the Great Barrier Reef, Australia
Scientific classification

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically live in compact colonies of many identical individual polyps. Corals species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

A coral "group" is a colony of myriad genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length. A set of tentacles surround a central mouth opening. An exoskeleton is excreted near the base. Over many generations, the colony thus creates a large skeleton characteristic of the species. Individual heads grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon.

Although some corals are able to catch small fish and plankton using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates in the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae. Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 ft). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia.

Other corals do not rely on zooxanthellae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3,300 metres (10,800 ft).[1] Some have been found on the Darwin Mounds, north-west of Cape Wrath, Scotland, and others as far north as off the coast of Washington State and the Aleutian Islands.

Taxonomy

Aristotle's pupil Theophrastus described the red coral, korallion in his book on stones, implying it was a mineral; but he described it as a deep-sea plant in his Enquiries on Plants, where he also mentions large stony plants that reveal bright flowers when under water in the Gulf of Heroes.[2] Pliny the Elder stated boldly that several sea creatures including sea nettles and sponges "are neither animals nor plants, but are possessed of a third nature (tertius natura)".[3] Petrus Gyllius copied Pliny, introducing the term zoophyta for this third group in his 1535 book On the French and Latin Names of the Fishes of the Marseilles Region; it is popularly but wrongly supposed that Aristotle created the term.[3] Gyllius further noted, following Aristotle, how hard it was to define what was a plant and what was an animal.[3]

The Persian polymath Al-Biruni (d. 1048) classified sponges and corals as animals, arguing that they respond to touch.[4] Nevertheless, people believed corals to be plants until the eighteenth century, when William Herschel used a microscope to establish that coral had the characteristic thin cell membranes of an animal.[5]

Presently, corals are classified as certain species of animals within the sub-classes Hexacorallia and Octocorallia of the class Anthozoa in the phylum Cnidaria.[6] Hexacorallia includes the stony corals and these groups have polyps that generally have a 6-fold symmetry. Octocorallia includes blue coral and soft corals and species of Octocorallia have polyps with an 8-fold symmetry, each polyp having eight tentacles and eight mesenteries.

Fire corals are not true corals, being in the order Anthomedusa (sometimes known as Anthoathecata) of the class Hydrozoa.[7]

Other Languages
Afrikaans: Koraal
العربية: مرجان (حيوان)
asturianu: Coral
تۆرکجه: کاقاانقان
বাংলা: প্রবাল
Bân-lâm-gú: San-ô͘
башҡортса: Мәрйен
беларуская: Карал
беларуская (тарашкевіца)‎: Карал
български: Корали
brezhoneg: Koural
català: Coralls
Чӑвашла: Мерчен
Cebuano: Kagaangan
čeština: Korál
Cymraeg: Cwrel
dansk: Koraldyr
Deutsch: Koralle
eesti: Korallid
Ελληνικά: Κοράλλι
español: Coral
Esperanto: Koralo
euskara: Koral
فارسی: مرجان
français: Corail
Gaeilge: Coiréal
客家語/Hak-kâ-ngî: Sân-fù
한국어: 산호
հայերեն: Կորալ
हिन्दी: मूँगा (जीव)
Ido: Koralio
Bahasa Indonesia: Koral
íslenska: Kórall
עברית: אלמוגים
ಕನ್ನಡ: ಹವಳ
ქართული: მარჯანი
Кыргызча: Кораллдар
Latina: Corallium
latviešu: Koraļļi
Lëtzebuergesch: Korallen
lietuvių: Koralas
македонски: Корал
Mìng-dĕ̤ng-ngṳ̄: Dăng-hù
Nederlands: Koraal (zoölogie)
日本語: サンゴ
Nordfriisk: Koralen
norsk nynorsk: Korall
Novial: Koralie
occitan: Coralh
oʻzbekcha/ўзбекча: Marjon
پنجابی: مرجان
polski: Koral
português: Coral
română: Coral
Runa Simi: Mullu
русский: Коралл
саха тыла: Коралл
Scots: Coral
සිංහල: කොරල්
Simple English: Coral
slovenščina: Korala
српски / srpski: Корал
srpskohrvatski / српскохрватски: Koral
svenska: Koralldjur
Tagalog: Sagay
தமிழ்: பவளம்
తెలుగు: ప్రవాళం
Türkçe: Koral (canlı)
українська: Корал
اردو: مرجان
Tiếng Việt: San hô
Winaray: Bagangbang
吴语: 珊瑚
ייִדיש: קאראל
粵語: 珊瑚
中文: 珊瑚