Coral: Chinese translation of Persian xuruhak. In Chinese, "coral" refers to "coral" in a narrow sense, which is a kind of lower coelenterate that preys on marine plankton in a broad sense. Broadly speaking, "coral" is not a single organism, but a combination of many corals and their secretions and bones, namely the so-called non-plant "coral tree" and non-mineral "coral reef".
Coral is a kind of marine cylindrical coelenterate, which is automatically fixed on the calcareous remains of ancestral corals in the white larval stage. Coral is the shell secreted by coral. The chemical composition of coral is mainly CaCO3, which exists in the form of microcrystalline calcite aggregate. There is also a certain amount of organic matter in the composition, which is mostly dendritic and vertical. Each individual coral has concentric circles and radial stripes on the cross section, and its color is often white, but there are also a little blue and black. Corals are not just like branches.
Coral's growing environment: It grows in tropical and subtropical areas where the temperature is higher than 20℃ at the equator and its vicinity, and in calm and clear rocks, terraces, slopes, cliffs and cracks with water depth of100-200m. Mainly produced in the Mediterranean.
Classification of corals:
1, by species:
Coralline algae is the largest class of coelenterates, all marine life. They are all hydra-type individual or group animals, and there is no jellyfish-type generation in their life history. The hydrozoa structure of coral algae is more complex than that of hydrozoa, and its body is symmetrical on two radiation lines. Common species such as red coral (Corallium rubrum), anemone (Metridium) and sea cactus (Cavernula). There are about 9000 species of coelenterates, which are usually divided into 3 classes, namely, about 2700 species of hydra; There are only more than 200 kinds of Scyphozoa; There are more than 6 100 species of corals. There are about 1 1,000 species of stony corals (1230:Madreporaria or Scleractinia); There are about 100 species of black coral and spiny coral (antipatharia); There are about 1, 200 species of [〔Gorgonacea〕] (or horny corals); There is only one kind of blue coral (Coenothecalia).
2. Ecological zoning:
According to the ecological environment and characteristics of stony corals, they can be divided into reef-building corals; Non-reef-building corals (or deep-water stony corals)
3, jewelry coral:
The use of coral by human beings can be traced back to ancient Greece and Rome. Red coral from the Mediterranean Sea was called Kowatari ("Persian Import") in Japan at that time, and was introduced to Japan via the Silk Road in Nara era (AD 7 10-784). In medieval Europe, corals were widely used to make ornaments and prayer beads for religious ceremonies.