Anthozoa in the context of "Coral"

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.

Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian.

Sea anemones (/əˈnɛm.ə.ni/ ə-NEM-ə-nee) are a group of predatory marine invertebrate animals constituting the order Actiniaria. Because of their colourful appearance, they are named after the Anemone, a terrestrial flowering plant. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia.As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.

A typical sea anemone is a single polyp attached to a hard surface by its base, but some species live in soft sediment, and a few float near the surface of the water. The polyp has a columnar trunk topped by an oral disc with a ring of tentacles and a central mouth. The tentacles can be retracted inside the body cavity or expanded to catch passing prey. They are armed with cnidocytes (stinging cells). In many species, additional nourishment comes from a symbiotic relationship with single-celled dinoflagellates, with zooxanthellae, or with green algae, zoochlorellae, that live within the cells. Some species of sea anemone live in association with clownfish, hermit crabs, small fish, or other animals to their mutual benefit.

Incertae sedis (Latin for 'of uncertain placement') or problematica is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty at specific taxonomic levels is indicated by incertae familiae (of uncertain family), incerti subordinis (of uncertain suborder), incerti ordinis (of uncertain order) and similar terms.

Macrobenthos consists of the organisms that live at the bottom of a water column and are visible to the naked eye. In some classification schemes, these organisms are larger than 1 mm; in another, the smallest dimension must be at least 0.5 mm. They include polychaete worms, pelecypods, anthozoans, echinoderms, sponges, ascidians, crustaceans.

The marine macrobenthos community is a critical component and reliable indicator of the biotic integrity of marine ecosystems, especially the intertidal ecosystems. On the one hand, macrobenthos plays a vital role in maintaining ecosystem functions, such as material cycling in sediments and energy flow in food webs. On the other hand, macrobenthos is relatively sedentary and therefore reflects the ambient conditions of sediments, in which many pollutants (e.g., heavy metals and organic enrichment) are ultimately partitioned.

Octocorallia, along with Hexacorallia, is one of the two extant classes of Anthozoa. It comprises over 3,000 species of marine and brackish animals consisting of colonial polyps with 8-fold symmetry, commonly referred to informally as "soft corals". It was previously known by the now unaccepted scientific names Alcyonacea and Gorgonacea, both deprecated c. 2022, and by the also deprecated name of Alcyonaria, in earlier times.

Its only two orders are Malacalcyonacea and Scleralcyonacea, which include corals such as those under the common names of blue corals, sea pens, and gorgonians (sea fans and sea whips). These animals have an internal skeleton secreted by their mesoglea, and polyps with typically eight tentacles and eight mesenteries. As is the case with all cnidarians, their complex life cycle includes a motile, planktonic phase (a larva called planula), and a later characteristic sessile phase.