coral-root: see orchid.

coral snake, name for poisonous New World snakes of the same family as the Old World cobras. About 30 species inhabit Mexico, Central America, and N South America; two are found in the United States. The Eastern coral snake (Micrurus fulvius), or harlequin snake, is found in the SE United States and N Mexico. It is a burrowing snake with a small, blunt head and a cylindrical body, averaging 21/2 ft (75 cm) in length. The body is ringed with bands of black, red, and yellow; the tail has yellow and black rings only. The Sonoran, or Western, coral snake (Micruroides euryxanthus) is a rather rare species found in the SW United States and NW Mexico. It is about 18 in. (45 cm) long and has much broader bands of yellow than those of the Eastern species. Coral snakes can be distinguished from a number of similarly colored harmless snakes by the fact that they are the only ones with red bands touching yellow ones. The venom of coral snakes, like that of cobras, acts on the nervous system and causes paralysis; the mortality rate among humans who are bitten is high. However, coral snakes are infrequently encountered because of their burrowing habits, and they seldom bite unless handled. They feed on other snakes and on lizards. Coral snakes are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Squamata, family Elapidae.

coral reefs, limestone formations produced by living organisms, found in shallow, tropical marine waters. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate (limestone). The accumulation of skeletal material, broken and piled up by wave action, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Although corals are found both in temperate and tropical waters, reefs are formed only in a zone extending at most from 30°N to 30°S of the equator; the reef-forming corals do not grow at depths of over 100 ft (30 m) or where the water temperature falls below 72°F; (22°C;). Corals are not the only, and in some cases not even the major, reef-forming organisms. Calcium carbonate is also deposited by coralline algae, the protozoan foraminiferans, some mollusks, echinoderms, and tube-building annelid worms. However, any reef formed by a biological community is usually called a coral reef.

Geologically, coral reefs are classified into three main types. Fringing reefs are coral platforms that are more or less continuous with the shore and exposed at low tide. Barrier reefs are separated from the shore by a wide, deep lagoon or surround a lagoon that has a central island. An atoll is a reef surrounding a lagoon that has no central island, with passages through the reef to the sea. It is generally believed that fringing reefs formed as a result of upward and outward growth of corals that became established on rocks near shore; there is disagreement about the nature of barrier reef and atoll formation. Charles Darwin postulated a progression from fringing reef to barrier reef to atoll, as a result of a slow, steady sinking of the seafloor that creates a lagoon and a simultaneous upward and outward growth of coral. Where entire volcanic islands sink, only the reef remains above water, forming an atoll. Not all scientists accept Darwin's proposal, but most current theories involve subsidence of the seafloor, although changes of the ocean level may also be involved.

Sediments accumulate on the lagoon side of atolls and support vegetation; in time the entire lagoon may fill, creating an island. Many such atolls and islands, common in the Pacific and Indian oceans, are inhabited. The Great Barrier Reef of NE Australia is the largest known complex of coral reefs. It is 10 to 90 mi (16-145 km) wide and about 1250 mi (2010 km) long, and is separated from the shore by a lagoon 10 to 150 mi (16-240 km) wide.

Reefs are under numerous environmental pressures, including damage from increased coastal development, water pollution, tourism, runoff containing agricultural chemicals, abrasion by ships' hulls and anchors, and smothering by upstream sedimentation. Coral reefs are sometimes destroyed in fishing when poison or dynamite are used to catch fish and by the harvesting of coral for use in jewelry. During the 1990s, many previously unknown diseases began attacking coral reefs worldwide, causing rapidly spreading damage.

coral bells: see saxifrage.

coral, small, sedentary marine animal, related to the sea anemone but characterized by a skeleton of horny or calcareous material. The skeleton itself is also called coral. Although most corals form colonies by budding, there are some solitary corals; in both types the individual animals, called polyps, resemble the sea anemone in form.

Corals grow in warm and temperate climates and in the cold water found at greater depths, but they are most abundant in warm, shallow water; over 200 coral species are found in the Great Barrier Reef of Australia. In many shallow-water species the polyps contain unicellular plants, which may provide the high oxygen concentration required by such corals.

Stony Corals

In the large group known as stony corals, or true corals (Madreporaria), each polyp secretes a cup-shaped skeleton, the theca, around itself. Some solitary corals of that group may reach a diameter of 10 in. (25 cm); in the colonial forms the individual polyps are usually under 1/8 in. (3 mm) long, but the colonies may be enormous. The body of each polyp is saclike, consisting of a wall of jellylike material surrounding a digestive cavity, with a single opening, the mouth, at the unattached end. The mouth is surrounded by tentacles used to capture small prey and is invaginated to form a pharynx leading into the body cavity. Thin sheets of tissue (mesentaries) extend radially from the wall to the pharynx, dividing the cavity. A second set of radial divisions is created by folds (septa) of the outer skeleton and body wall, which extend upward from the floor of the body cavity. Reproduction occurs both sexually and by budding. Sexual reproduction is by means of eggs and sperm, which are produced in the mesentaries and shed into the water. Fertilization results in a free-swimming larva, which attaches to a surface and secretes a skeleton, becoming (in colonial forms) the parent of a new colony.

As new polyps are produced by budding they remain attached to each other by thin sheets of living tissue as well as by newly secreted skeletal material. The great variety in the form of various colonial corals, which may be treelike and branching, or rounded and compact, depends chiefly on the method of budding of the particular species. In the brain corals, for example, each theca merges with the one next to it on either side, forming long rows of polyps separated by deep channels. In some of the branching corals the polyps occupy small, discrete pits on the surface of the skeleton. As a colonial coral produces more polyps the lower members die and new layers are built up on the old skeleton, forming a large mass. In tropical and subtropical regions these massive corals, along with other plants and animals, may form a coral reef. Most of the reef-forming corals belong to the stony coral group.

Soft Corals

The soft corals (Alcyonaria) are a group of soft, often feathery forms, with skeletons composed of calcareous or horny particles imbedded in the body wall. Each polyp of a soft coral has eight tentacles. Among the well-known soft corals are the sea pen, sea pansy, whip coral, and organpipe coral. The precious red coral (Corallium) of the Mediterranean Sea, used for jewelry, also belongs to that group. The spicules of its skeleton are fused together.

Classification

Stony and soft corals are classified in the phylum Cnidaria, class Anthozoa.

Coral Springs, city (1990 pop. 79,443), Broward co., SE Fla.; inc. 1963. Largely residential, it is a city that has grown rapidly along with the southern Florida and Fort Lauderdale area. The population of Coral Springs nearly doubled between 1980 and 1990.

Coral Sea Islands, external territory of Australia, comprising scattered small islands and reefs spread over c.400,000 sq mi (1,035,995 sq km) of the South Pacific Ocean, E of the Great Barrier Reef, off NE Australia. The islands, uninhabited except for a meteorological station on the Willis Islets, became a territory in 1969.

Coral Sea, southwest arm of the Pacific Ocean, between Australia, New Guinea, and Vanuatu. The Great Barrier Reef lies along its western edge. During World War II it was the scene of a major U.S. victory against the Japanese in 1942; the battle, fought by aircraft near the Louisiade Archipelago, checked the southward expansion of the Japanese.

Coral Gables, city (1990 pop. 40,091), Miami-Dade co., SE Fla., SW of Miami; inc. 1925. Founded at the height of the Florida land boom, Coral Gables is a noted planned city, with tree-lined boulevards and Mediterranean-style buildings. Originally heavily residential, it now houses many inter-American, in particular Latin American, offices of large corporations; its proximity to Miami International Airport has aided the city's development and promoted tourism. The Univ. of Miami is in Coral Gables.

Cape Coral, city (1990 pop. 74,991), Lee co., SW coastal Fla., located on an estuary of the Caloosahatchee River; inc. 1970. It is mostly a residential city that has grown rapidly along with the southern Florida area. Two industrial parks are in the vicinity, and boat building is an industry. The Univ. of South Florida is located in nearby Ft. Meyers. Cape Coral has a cultural center and a historical museum. The city's population more than doubled between 1980 and 1990.

Any of about 90 species of strongly patterned burrowing elapids. “True” forms are limited to the New World, chiefly the tropics, but similar species live in Asia and Africa. Secretive and docile, coral snakes rarely bite when handled, but the venom of some can kill a person. Most prey on other snakes. More than 50 species in the largest genus, Micrurus, range from the southern U.S. to Argentina. They are ringed with red, black, and yellow or white. The eastern coral snake, or harlequin snake (Micrurus fulvius), ranges from North Carolina and Missouri in the U.S. to northeastern Mexico and is about 30 in. (76 cm) long, with wide bands of red and black separated by yellow. The rhyme “Red on yellow, dangerous fellow” distinguishes it from similarly coloured but harmless species.

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Ridge or hummock formed in shallow ocean areas from the external skeletons of corals. The skeleton consists of calcium carbonate (CaCO₃), or limestone. A coral reef may grow into a permanent coral island, or it may take one of four principal forms. Fringing reefs consist of a flat reef area around a nonreef island. Barrier reefs may lie a mile or more offshore, separated from the landmass by a lagoon or channel. Atolls are circular reefs without a central landmass. Patch reefs have irregular tablelike or pinnacle features. Smaller patches occur inside atoll lagoons; larger patches occur as isolated parts of any of the other three reef categories, and they sometimes occur completely separate from other kinds of reefs.

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Coral reef enclosing a lagoon. Atolls consist of ribbons of reef that may not be circular but that are closed shapes, sometimes miles across, around a lagoon that may be 160 ft (50 m) deep or more. Most of the reef itself is usually below the water surface; around the rim along the top are usually low, flat islands or more continuous strips of low, flat land.

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Any of about 2,300 species of marine cnidarians in the class Anthozoa that are characterized by stonelike, horny, or leathery skeletons (external or internal). The skeletons of these animals are also called coral. Corals are found in warm seas worldwide. The body is of the polyp type. Soft, horny, and blue corals are colonial in habit (i.e., they live in large groups). Stony corals, the most familiar and widely distributed forms, are both colonial and solitary. Atolls and coral reefs, which are composed of stony coral, grow at an average rate of 0.2–1.1 in. (0.5–2.8 cm) per year. Seealso sea fan.

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Part of the South Pacific Ocean. It is located between Queensland, Australia, on the west and Vanuatu and New Caledonia on the east, and bordered on the north by Papua New Guinea and the Solomon Islands. Occupying an area of 1,849,800 sq mi (4,791,000 sq km), it merges with the Tasman Sea and Solomon Sea and is connected to the Arafura Sea via the Torres Strait. It was named for its many coral formations, including the Great Barrier Reef. During World War II it was the scene of a strategic U.S. naval and air victory over the Japanese (1942).

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