New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Coral

Corals are marine animals from the class Anthozoa and exist as small sea anemone-like polyps, typically in colonies of many identical individuals. The group includes 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 actually formed of thousands of individual but genetically identical polyps, each polyp only a few millimeters 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 gametes simultaneously over a period of one to several nights around a full moon.

Although corals can catch plankton using stinging cells on their tentacles, these animals obtain most of their nutrients from symbiotic unicellular algae called zooxanthellae. Consequently, 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 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 have associated algae and can live in much deeper water, such as in the Atlantic, with the cold-water genus Lophelia surviving as deep as 3000 m. Corals have also been found off the coast of Washington State and the Aleutian Islands in Alaska.

While a coral head appears to be a single organism, it is actually a head of many individual, yet genetically identical, polyps. The polyps are multicellular organisms that feed on a variety of small organisms, from microscopic plankton to small fish.

Polyps are usually a few millimeters in diameter, and are formed by a layer of outer epithelium and inner jellylike tissue known as the mesoglea. They are radially symmetrical with tentacles surrounding a central mouth, the only opening to the stomach or coelenteron, through which both food is ingested and waste expelled.

Related Stories
 


Plants & Animals News

October 29, 2025

Researchers at QUT uncovered how corals reattach to reefs through a three-phase process involving tissue transformation, anchoring, and skeleton formation. Differences among species reveal why some corals grow and attach faster than others. ...
Beneath the ice of Antarctica’s Weddell Sea, scientists discovered a vast, organized city of fish nests revealed after the colossal A68 iceberg broke away. Using robotic explorers, they found over ...
An international team of researchers led by scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig, working with 15 collaborators around the world, has conducted the most comprehensive study yet of lifespan differences ...
Extinction rates are not spiraling upward as many believe, according to a large-scale study analyzing 500 years of data. Researchers found that species losses peaked about a century ago and have decreased since, with different drivers shaping past ...
A team of researchers has developed a floral-scented fungus that tricks mosquitoes into approaching and dying. The fungus emits longifolene, a natural scent that irresistibly draws them in. It’s harmless to humans, inexpensive to produce, and ...
Dinosaurs weren’t dying out before the asteroid hit—they were thriving in vibrant, diverse habitats across North America. Fossil evidence from New Mexico shows that distinct “bioprovinces” of dinosaurs existed until the very end. Their ...
New research shows that hippos lived in central Europe tens of thousands of years longer than previously thought. Ancient DNA and radiocarbon dating confirm they survived in Germany’s Upper Rhine Graben during a milder Ice Age phase. Closely ...
Reptiles don’t just pee, they crystallize their waste. Researchers found that snakes and other reptiles form tiny uric acid spheres, a water-saving evolutionary trick. This discovery could illuminate how to prevent gout and kidney stones in ...
In the mist-shrouded mountains of New Guinea, a Czech researcher has achieved a world-first — capturing photos, video, and data of the elusive Subalpine Woolly Rat, Mallomys istapantap. Once known only from museum specimens, this giant, shaggy ...
Common dolphins in the North Atlantic are living significantly shorter lives, with female longevity dropping seven years since the 1990s. Researchers found this decline by analyzing stranded dolphins, revealing a 2.4% drop in population growth ...
Naked mole-rats seem to have found nature’s cheat code for longevity. Scientists discovered that small tweaks in one of their proteins make it better at fixing DNA damage, helping the animals resist aging. Even fruit flies with the same changes ...
Researchers have developed a light-emitting sugar probe that exposes how marine microbes break down complex carbohydrates. The innovative fluorescent tool allows scientists to visualize when and where sugars are degraded in the ocean. This ...

Latest Headlines

updated 12:56 pm ET