''Galaxea'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of colonial

stony coral Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...

s in the family

Euphylliidae Euphylliidae (Greek language, Greek eu-, true; Greek alphabet, Greek phyllon, leaf) are known as a family of Polyp (zoology), polyped Stony coral, stony corals under the order Scleractinia. This Family (biology), family consists of multiple Genus ...

. Common names include crystal, galaxy, starburst and tooth coral. They are abundant on

reefs A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave eros ...

in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region and the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

.Family Oculinidae: ''Galaxea''
Horizon. Retrieved 2011-12-16. They are found in water less than deep and favour turbid sites. They are sometimes kept in

reef aquaria A reef aquarium or reef tank is a marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the tropical coral reef environment. A reef aquarium requires appropriately in ...

.''Galaxea''
Tidal Gardens. Retrieved 2011-12-16.

Description

The colonies of ''Galaxea'' have various forms according to species. ''G. fascicularis'' forms long, thin columns and is one of the largest corals known. ''G. paucisepta'' and '' G. longisepta'' form flat plates, ''G. acrhelia'' is arborescent and other species form domes and rounded mounds. Their colours are mostly olives or browns but they are often tinged with purple. The

corallite A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...

s in which the individual polyps sit are small and crowded and have raised edges or may even be stalked. There are a large number of fine

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

on the edge of the corallites, arranged in whorls and protruding as sharp ridges. The polyps contain

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...

s called

zooxanthellae Zooxanthellae (; zooxanthella) is a colloquial term for single-celled photosynthetic organisms that are able to live in symbiosis with diverse marine invertebrates including corals, jellyfish, demosponges, and nudibranchs. Most known zooxanthell ...

and grow in shallow water to maximise the uptake of sunlight. They often feed in the day, extending yellowish or greenish, often white tipped tentacles. They have certain specialised sweeper tentacles, long defensive organs, tipped with powerful

cnidocyte A cnidocyte (also known as a cnidoblast) is a type of cell containing a large secretory organelle called a ''cnidocyst'', that can deliver a sting to other organisms as a way to capture prey and defend against predators. A cnidocyte explosively ...

s which discourage other corals from living close by.

Species

The World Register of Marine Species lists the following species: *'' Galaxea acrhelia'' Veron, 2000 *'' Galaxea alta'' Nemenzo, 1979
*'' Galaxea astreata'' (Lamarck, 1816) *'' Galaxea cryptoramosa'' Fenner & Veron, 2002 *'' Galaxea fascicularis'' (Linnaeus, 1767) *'' Galaxea horrescens'' (Dana, 1846) *'' Galaxea lauensis'' Hoffmeister, 1945 † *'' Galaxea longisepta'' Fenner & Veron, 2000 *'' Galaxea pauciradiata'' (Blainville, 1830) *'' Galaxea paucisepta'' Claereboudt, 1990

References

{{Taxonbar, from=Q3094518 Euphylliidae Taxa named by Lorenz Oken Scleractinia genera