Anthozoa
Stony corals, Scleractinia
Scientific classification
Kingdom: Animalia Phylum: Cnidaria Class: Anthozoa Ehrenberg, 1831

Anthozoa is a class within the phylum Cnidaria that contains the sea anemones and corals. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows. Some anthozoans can also reproduce asexually through budding.

All cnidarian species can feed by catching prey with nematocysts, sea anemones capable of catching fish and corals catching plankton. Some of the species also harbour a type of algae, dinoflagellates called zooxanthellae, in a symbiotic relationship; the reef building corals known as hermatypic corals rely on this symbiotic relationship particularly. The zooxanthellae benefit by using nitrogenous waste and carbon dioxide produced by the host, and the cnidarian gains photosynthetic capability and increased calcium carbonate production in hermatypic corals.^[1]

Anemonies and certain species of coral live in isolation, however most corals form colonies of genetically identical polyps; these polyps closely resemble anemonies in structure, although are generally considerably smaller. Most kinds of stony coral live in all parts of the underwater world.

Giant green anemone, likely Epicystis crucifer, Southern California

Phylogeny

The two subclasses are divided into a number of orders^[2] and a series of orders.^[3][4][5][6], extinct orders from the Paleozoic (570-245 m.y.a.)^[7] are marked with †.

• Subclass Alcyonaria (= Octocorallia) (8-way symmetry)
  • Alcyonacea (soft corals)
  • Gorgonacea (sea fans, sea feathers)
  • Helioporacea (= Coenothecalia) (Indo-Pacific blue coral)
  • Pennatulacea (sea pens, sea pansies)
  • Stolonifera (organ-pipe coral, tree fern coral)
  • Telestacea (soft corals)
• Subclass Zoantharia (= Hexacorallia) (6-way symmetry)
  • Ceriantharia (tube-dwelling anemones)
  • Actiniaria (sea anemones)
  • Corallimorpharia
  • Numidiaphyllida †
  • Scleractinia (= Madreporaria) (stony corals)
  • Kilbuchophyllida †
  • Antipatharia (black corals, thorny corals)
  • Zoanthidea
  • Heterocorallia †
  • Rugosa † (= Tetracoralla) (horned corals)
  • Heliolitida †
  • Tabulata † (tabulate corals)
  • Cothoniida †
  • Tabuloconida †
  • Ptychodactiaria

References

1. Contribution to the BUFUS Newsletter, Field excursion to Milne Bay Province - Papua New Guinea, Madl and Yip 2000
2. Fautin, Daphne G. and Romano, Sandra L. (2000). Anthozoa. Sea Anemones, Corals, Sea Pens.. The Tree of Life Web Project. Retrieved on 2006-03-31.
3. Chen, C. A., D. M. Odorico, M. ten Lohuis, J. E. N. Veron, and D. J. Miller (June 1995). "Systematic relationships within the Anthozoa (Cnidaria: Anthozoa) using the 5'-end of the 28S rDNA". Molecular Phylogeny and Evolution 4 (2): 175-183. PMID 7663762. 
4. France, S. C., P. E. Rosel, J. E. Agenbroad, L. S. Mullineaux, and T. D. Kocher (March 1996). "DNA sequence variation of mitochondrial large-subunit rRNA provides support for a two subclass organization of the Anthozoa (Cnidaria)". Molecular Marine Biology and Biotechnology 5 (1): 15-28. PMID 8869515. 
5. Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey (2006). Subclass Alcyonaria. The Animal Diversity Web (online). Retrieved on 2006-03-31.
6. Ben Kotrc (2005). Anthozoa: Subgroups. Fossil Groups. University of Bristol. Retrieved on 2007-04-09.
7. Oliver, W. A., Jr. (1996). "Origins and relationships of Paleozoic coral groups and the origin of the Scleractinia", in G. D. J. Stanley (ed.): Paleobiology and Biology of Corals. Columbus, Ohio: The Paleontological Society, 107-134. 

Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Anthozoa". Image Credit.

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