Alcyonacea, or soft corals, are an order of

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and se ...

s. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", that produce a more or less hard skeleton, though quite different from "true" corals (

Scleractinia 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 ...

). These can be found in suborders Holaxonia, Scleraxonia, and Stolonifera. They are sessile

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...

cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

ns that are found throughout the oceans of the world, especially in the deep sea, polar waters,

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

and

subtropics The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° nort ...

. Common names for subsets of this order are sea fans and sea whips; others are similar to the sea pens of related order Pennatulacea. Individual tiny polyps form colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across, but only a few inches thick. They may be brightly coloured, often purple, red, or yellow. Photosynthetic gorgonians can be successfully kept in captive aquaria. About 500 different species of gorgonians are found in the oceans of the world, but they are particularly abundant in the shallow waters of the Western Atlantic, including

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

Bermuda ) , anthem = "God Save the King" , song_type = National song , song = "Hail to Bermuda" , image_map = , map_caption = , image_map2 = , mapsize2 = , map_caption2 = , subdivision_type = Sovereign state , subdivision_name = , es ...

, and the West Indies.

Anatomy

The structure of a gorgonian colony varies. In the suborder Holaxonia, skeletons are formed from a flexible, horny substance called gorgonin. The suborder Scleraxonia species are supported by a skeleton of tightly grouped calcareous spicules. Also, some species encrust like coral. Measurements of the gorgonin and calcite within several long-lived species of gorgonians can be useful in

paleoclimatology Paleoclimatology (British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...

and

paleoceanography Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models ...

, as their skeletal growth rate and composition are highly correlated with seasonal and climatic variation.

Features

Soft corals contain minute, spiny skeletal elements called

sclerite A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

s, useful in species identification. Sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators. In the past, soft corals were thought to be unable to lay new foundations for future corals, but recent findings suggest that colonies of the leather-coral genus ''

Sinularia ''Sinularia'' is a genus of soft coral in the family Alcyoniidae. They are commonly known as leather corals and currently have 166 described species In biology, a species is the basic unit of classification and a taxonomic rank of an o ...

'' are able to cement sclerites and consolidate them at their base into alcyonarian spiculite, thus making them reef builders. Unlike

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, most soft corals thrive in nutrient-rich waters with less intense light. Almost all use symbiotic photosynthetic

zooxanthella Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus '' Sym ...

as a major energy source. However, most readily eat any free-floating food, such as zooplankton, out of the water column. They are integral members of the reef ecosystem and provide habitat for fish, snails, algae, and a diversity of other marine species. Despite being dominated by "soft corals", the order Alcyonacea now contains all species known as "gorgonian corals", that produce a hard skeleton made from gorgonin, a protein unique to the group that makes their skeletons quite different from "true" corals (

). These "gorgonion corals" can be found in suborders Holaxonia, Scleraxonia, and Stolonifera. Many soft corals are easily collected in the wild for the reef aquarium hobby, as small cuttings are less prone to infection or damage during shipping than stony corals. Nevertheless, home-grown specimens tend to be more adaptable to aquarium life and help conserve wild reefs. Soft corals grow quickly in captivity and are easily divided into new individuals, and so those grown by

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

are often hardier and less expensive than imported corals from the wild.

Ecology

Each gorgonian polyp has eight

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s, which catch

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

and particulate matter for consumption. This process, called

filter feeding Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

, is facilitated when the "fan" is oriented across the prevailing current to maximise water flow to the gorgonian, hence food supply. Some gorgonians contain algae, or

e. This

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...

relationship assists in giving the gorgonian nutrition by

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

. Gorgonians possessing zooxanthellae are usually characterized by brownish polyps. Gorgonians are found primarily in shallow waters, though some have been found at depths of several thousand feet. The size, shape, and appearance of gorgonians can be correlated with their location. The more fan-shaped and flexible gorgonians tend to populate shallower areas with strong currents, while the taller, thinner, and stiffer gorgonians can be found in deeper, calmer waters. Other fauna, such as

hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialize ...

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

, and brittle stars, are known to dwell within the branches of gorgonian colonies. The

pygmy seahorse The pygmy seahorses comprise several species of tiny seahorse in the syngnathid family (biology), family or Syngnathidae (seahorses and pipefish). Family Syngnathidae is part of order Syngnathiformes, which contains fishes with fused jaws that su ...

not only makes certain species of gorgonians its home, but also closely resembles its host, thus is well camouflaged. Two species of pygmy seahorse, ''

Hippocampus bargibanti ''Hippocampus bargibanti'', also known as Bargibant's seahorse or the pygmy seahorse, is a seahorse of the family Syngnathidae found in the central Indo-Pacific area. It is tiny, usually less than in size and lives exclusively on fan corals.Ep ...

'' and ''

Hippocampus denise ''Hippocampus denise'', also known as Denise's pygmy seahorse or the yellow pygmy seahorse, is a seahorse of the family Syngnathidae native to the western Pacific. Description Denise's pygmy seahorse is a small fish which can reach a maximum l ...

,'' are obligate residents on gorgonians. ''H. bargibanti'' is limited to two species in the single genus ''Muricella''. Gorgonians produce unusual

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

s in their tissues, particularly

diterpene Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being ...

s, and some of these are important candidates for new drugs. These compounds may be part of the chemical defenses produced by gorgonians to render their tissue distasteful to potential predators.

Bottlenose dolphin Bottlenose dolphins are aquatic mammals in the genus ''Tursiops.'' They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus definitively contains two species: the comm ...

s in the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

have been observed swimming against these tissues, in what is thought to be an attempt to take advantage of the antimicrobial qualities of

diterpenes Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate bei ...

. Despite these chemical defenses, the tissues of gorgonians are prey for flamingo tongue snails of the genus '' Cyphoma,''

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

s, the fireworm ''Hermodice'' spp., and their polyps are food for

butterflyfish The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atlan ...

es. Amongst the nudibranchs which feed on soft corals and sea fans are the Tritoniidae and the genus ''

Phyllodesmium ''Phyllodesmium'' is a genus of predatory sea slugs, aeolid nudibranchs, marine gastropod molluscs in the family Facelinidae.Bouchet, P. (2012). ''Phyllodesmium'' Ehrenberg, 1831. Accessed through: World Register of Marine Species at http://www. ...

'' which specialises in eating '' Xenia'' species.

Suborders and families

The World Register of Marine Species lists these suborders and families: * suborder

Alcyoniina Alcyoniina is a suborder of soft coral found mainly in the Pacific and Indian oceans The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth ...

** family

Acrophytidae Acrophytidae is a family of corals belonging to the order Alcyonacea Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian cora ...

McFadden & Ofwegen, 2017 ** family

Alcyoniidae Alcyoniidae is a family of leathery or soft corals in the phylum Cnidaria.Leathery cor ...

Lamouroux, 1812 ** family Aquaumbridae Breedy, van Ofwegen & Vargas, 2012 ** family

Corymbophytidae ''Corymbophyton'' is a monotypic genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa ...

McFadden & Ofwegen, 2017 ** family Leptophytidae McFadden & Ofwegen, 2017 ** family

Nephtheidae Nephtheidae is a family of soft corals in the phylum Cnidaria. Members of this family are known as carnation corals, tree corals or colt soft corals. They are very attractive and show a wide range of rich and pastel colours including reds, pinks ...

Gray, 1862 ** family

Nidaliidae Nidaliidae is a family of soft corals in the phylum Cnidaria. Some members of this family are similar in appearance to gorgonians (sea fans). They are difficult to keep in the reef aquarium because they do not contain symbiotic zooxanthellae and ...

Gray, 1869 ** family Paralcyoniidae Gray, 1869 ** family

Xeniidae Xeniidae is a family of soft coral in the order Alcyonacea. Predators Predatory sea slugs of the genus '' Phyllodesmium'' are reported to feed on Xeniidae species. Representatives of this family have been observed to provide shelter to juvenil ...

Ehrenberg, 1828 * suborder

Calcaxonia Calcaxonia is a suborder of soft corals in the order Alcyonacea Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", ...

** family

Chrysogorgiidae Chrysogorgiidae is a family of soft corals in the suborder Calcaxonia. References * Bayer, F.M. and K.M. Muzik. 1976. New genera and species of the holaxonian family Chrysogorgiidae (Octocorallia: Gorgonacea). Zoologische Mededelingen (Leiden ...

Verrill, 1883 ** family

Ellisellidae Ellisellidae is a family of soft corals Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", that produce a more o ...

Gray, 1859 ** family

Ifalukellidae Ifalukellidae is a family of corals belonging to the order Alcyonacea Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian co ...

Bayer, 1955 ** family Isididae Lamouroux, 1812 ** family

Primnoidae Primnoidae is a family of soft corals Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian corals", that produce a more or l ...

Milne Edwards, 1857 * suborder Holaxonia ** family

Acanthogorgiidae Acanthogorgiidae is a family of cnidarians belonging to the order Alcyonacea. Genera: * '' Acanthogorgia'' Gray, 1857 * '' Anthogorgia'' Verrill, 1868 * '' Ascolepis'' * '' Calcigorgia'' Broch, 1935 * '' Calicogorgia'' Thomson & Henderson, 1906 * ...

Gray, 1859 ** family

Dendrobrachiidae Dendrobrachiidae is a family of cnidarians belonging to the order Alcyonacea Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgon ...

Brook, 1889 ** family

Gorgoniidae Gorgoniidae is a family of soft corals, a member of the subclass Octocorallia in the phylum Cnidaria. Nearly all the genera and species are native to the east and west coasts of America. Characteristics Originally the members of the family Go ...

Lamouroux, 1812 ** family Keroeididae Kinoshita, 1910 ** family

Plexauridae Plexauridae is a family of marine colonial octocorals in the phylum Cnidaria. Members of this family are found in shallow tropical and subtropical seas. Many species contain symbiotic photosynthetic protists called zooxanthellae. Characterist ...

Gray, 1859 * suborder Protoalcyonaria ** family Taiaroidae Bayer & Muzik, 1976 * suborder Scleraxonia ** family

Anthothelidae Anthothelidae is a family of corals, a member of the phylum Cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the lat ...

Broch, 1916 ** family

Briareidae Briareidae is a family of corals, a member of the phylum Cnidaria. Genera Genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biolog ...

Gray, 1859 ** family

Coralliidae Coralliidae, also known as precious corals, is a taxonomic family of soft corals belonging to the phylum Cnidaria of the family Scleraxonia. These sessile corals are one of the most dominant members of hard-bottomed benthic environments such as ...

Lamouroux, 1812 ** family

Melithaeidae ''Melithaeidae'' is a family of corals in the suborder Scleraxonia. Members of the family are commonly known as sea fans and are found on reefs in the tropical regions of the Indo-Pacific.Paragorgiidae Paragorgiidae is a family of corals, a member of the phylum Cnidaria. Genera Genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of bio ...

Kükenthal, 1916 ** family

Parisididae ''Parisis'' is a genus of corals in the monotypic family Parisididae. Species Species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often ...

Aurivillius, 1931 ** family Spongiodermidae Wright & Studer, 1889 ** family

Subergorgiidae Subergorgiidae is a family of corals, a member of the phylum Cnidaria. Genera Genera in this family include: * ''Annella ''Annella'' is a genus of soft corals Alcyonacea, or soft corals, are an order of corals. In addition to the flesh ...

Gray, 1859 ** family Victorgorgiidae Moore, Alderslade & Miller, 2017 * suborder Stolonifera ** family Acrossotidae Bourne, 1914 ** family Arulidae McFadden & van Ofwegen, 2012 ** family Clavulariidae Hickson, 1894 ** family Coelogorgiidae Bourne, 1900 ** family Cornulariidae Dana, 1846 ** family

Pseudogorgiidae ''Pseudogorgia'' is a monotypic genus of corals Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important ...

Utinomi & Harada, 1973 ** family Tubiporidae Ehrenberg, 1828 * family Acanthoaxiidae van Ofwegen & McFadden, 2010 * family

Haimeidae Haimeidae is a family of cnidarians belonging to the order Alcyonacea Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian cora ...

Wright, 1865 * family Paramuriceidae Bayer, 1956 * family Parasphaerascleridae McFadden & van Ofwegen, 2013 * family Viguieriotidae File:Alcyonium acaule Marion, 1878 3.jpg, ''

Alcyonium acaule ''Alcyonium acaule'' or Mediterranean sea-finger is a species of soft coral in the family Alcyoniidae. It is found at moderate depths on shaded rocks in the Mediterranean Sea and adjoining parts of the Atlantic Ocean. Description Mediterranea ...

'', an alcyoniid File:Dendronephthya hemprichi at Gilli Lawa Laut.JPG, ''

Dendronephthya hemprichi ''Dendronephthya hemprichi'' is a common soft coral found from Red Sea to Western Pacific. It is usually pink or orange with transparent trunk and it grows up to 70 cm. It exists at 30° N latitude.Dahan, M. & Benayahu, Y. 1993. Reproduct ...

'', a nephtheid File:Siphonogorgia godeffroyi (Pink soft coral).jpg, ''

Siphonogorgia godeffroyi ''Siphonogorgia godeffroyi'', the cherry blossom coral or Godeffroy's Soft Coral, is a species of soft coral in the family Nidaliidae. It is native to the central Indo-Pacific region. Its range includes Indonesia, the Philippines and Papua New G ...

'', a nidaliid File:Maasella edwardsi (de Lacaze-Duthiers, 1888).jpg, '' Maasella edwardsi'', a paralcyoniid File:Pulsating xenid, Heteroxenia fuscescens, a soft coral that pulsates rhythmically around 40 times a minute (6163181047).jpg, ''

Heteroxenia fuscescens The pulsating xenid (''Heteroxenia fuscescens'') is a species of soft coral in the family Xeniidae. The species was first described in 1834 by Christian Gottfried Ehrenberg as ''Xenia fuscescens''. Description The polyps of ''Heteroxenia fusc ...

'', a xeniid File:Iridigorgia sp.jpg, '' Iridigorgia'' sp., a chrysogorgiid File:Sea Whip (Ellisella sp.) (8486549324).jpg, '' Ellisella'' sp., an ellisellid File:Isidella tentaculum - NOAA.jpg, '' Isidella tentaculum'', an isidid File:Plumarella pellucida.jpg, '' Plumarella pellucida'', a primnoid File:Pygmy Seahorse -Lembeh Straits.jpg, ''

Muricella ''Muricella'' is a genus of corals belonging to the family Acanthogorgiidae. The species of this genus are found in Pacific and Indian Ocean, Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben ...

'' sp., an acanthogorgiid File:Gorgonia ventalina, Bahamas.jpg, ''

Gorgonia ventalina ''Gorgonia ventalina'', the common sea fan and purple sea fan, is a species of sea fan, an octocoral in the family Gorgoniidae. It is found in the western Atlantic Ocean and the Caribbean Sea. Description ''G. ventalina'' is a fan-shaped col ...

'', a gorgoniid File:Paramuricea clavata (Risso, 1826) 5.jpg, ''

Paramuricea clavata ''Paramuricea clavata'', the violescent sea-whip, is a species of colonial soft coral in the family Plexauridae. It is found in shallow seas of the north-eastern Atlantic Ocean and the north-western Mediterranean Sea as well as Ionian Sea. This ...

'', a paramuriceid File:Muricea elongata.jpg, '' Muricea elongata'', a plexaurid File:Anthothela grandiflora.jpg, '' Anthothela grandiflora'', an anthothelid File:Briareum 2.JPG, ''

Briareum ''Briareum'' is a genus of soft corals in the family Briareidae Briareidae is a family of corals, a member of the phylum Cnidaria. Genera Genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living ...

'' sp., a briareid File:Corallium rubrum (Linnaeus, 1758) 11.jpg, ''

Corallium rubrum Precious coral, or red coral, is the common name given to a genus of marine corals, ''Corallium''. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink-orange skeleton, which is used for ma ...

'', a coralliid File:Acabaria splendens.jpg, '' Acabaria splendens'', a melithaeid File:Expl0924 - Flickr - NOAA Photo Library.jpg, '' Paragorgia arborea'', a paragorgiid File:Gorgone de Mayotte.jpg, ''

Annella mollis ''Annella mollis (Subergorgia mollis)'' is a species of soft corals Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "gorgonian cora ...

'', a subergorgiid File:Pachiclavularia viridis.JPG, '' Clavularia viridis'', a clavulariid File:Cornularia cornucopiae.jpg, '' Cornularia cornucopiae'', a cornulariid File:Tubipora purpurea-Musée zoologique de Strasbourg.jpg, '' Tubipora musica'', Tubiporidae File:Iciligorgia schrammi.jpg, '' Iciligorgia schrammi''

References

External links

The Marine Fauna Gallery of Norway

Gorgonian Corals
{{Taxonbar, from=Q137552, from2=Q1365073 Octocorallia Cnidarian orders