Alcyonacea

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Soft coral
Cladiella.JPG
Cladiella sp.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Cnidaria
Class: Octocorallia
Order: Alcyonacea
Lamouroux, 1812 [1]
Suborders

See text

Synonyms
  • Gorgonacea

Alcyonacea are an order of sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. Whilst not in a strict taxonomic sense, Alcyonacea are commonly known as soft corals. The term "soft coral" generally applies to organisms in the two orders Pennatulacea and Alcyonacea with their polyps embedded within a fleshy mass of coenenchymal tissue. [2] Consequently, the term "gorgonian coral" is commonly handed to multiple species in the order Alcyonacea that produce a mineralized skeletal axis (or axial-like layer) composed of calcite and the proteinaceous material gorgonin only and corresponds to only one of several families within the formally accepted taxon Gorgoniidae (Scleractinia). These can be found in order Malacalcyonacea (taxonomic synonyms of include (unnacepted): Alcyoniina, Holaxonia, Protoalcyonaria, Scleraxonia, and Stolonifera. [3] They are sessile colonial cnidarians that are found throughout the oceans of the world, especially in the deep sea, polar waters, tropics and subtropics. 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. [4] 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.

Contents

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, Bermuda, and the West Indies. [5]

Anatomy

Venus fan (Gorgonia flabellum), Caribbean Sea at Goat Bay (Bahia de la Chiva) on Vieques Island, Puerto Rico Venusin vejar.jpg
Venus fan ( Gorgonia flabellum ), Caribbean Sea at Goat Bay (Bahía de la Chiva) on Vieques Island, Puerto Rico
Gorgonian with reproductive stage, Caribbean Sea at Cabrits National Park, Dominica Gorgoniidae-Reproduction.jpg
Gorgonian with reproductive stage, Caribbean Sea at Cabrits National Park, Dominica
A close-up of an alcyonacean showing individual polyps 1898 aquaimages.jpg
A close-up of an alcyonacean showing individual polyps

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. [6]

Measurements of the gorgonin and calcite within several long-lived species of gorgonians can be useful in paleoclimatology and paleoceanography, as their skeletal growth rate and composition are highly correlated with seasonal and climatic variation. [7] [8] [9]

Features

Soft corals contain minute, spiny skeletal elements called sclerites, 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 are able to cement sclerites and consolidate them at their base into alcyonarian spiculite, [10] thus making them reef builders.

Unlike stony corals, most soft corals thrive in nutrient-rich waters with less intense light. Almost all use symbiotic photosynthetic zooxanthella 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 (Scleractinia). 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 are often hardier and less expensive than imported corals from the wild.

Ecology

Purple sea whip gorgonian Gorgonian.Mgiangrasso.jpg
Purple sea whip gorgonian
Fossil gorgonian holdfast on a Miocene limestone surface, Czech Republic GorgonianHoldfastMiocene.JPG
Fossil gorgonian holdfast on a Miocene limestone surface, Czech Republic

Each gorgonian polyp has eight tentacles, which catch plankton and particulate matter for consumption. This process, called filter feeding, 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 zooxanthellae. This symbiotic relationship assists in giving the gorgonian nutrition by photosynthesis. 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. [4] [6] 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. [4]

Other fauna, such as hydrozoa, bryozoa, and brittle stars, are known to dwell within the branches of gorgonian colonies. [11] The pygmy seahorse not only makes certain species of gorgonians its home, but also closely resembles its host, thus is well camouflaged. [12] Two species of pygmy seahorse, Hippocampus bargibanti and Hippocampus denise, are obligate residents on gorgonians. H. bargibanti is limited to two species in the single genus Muricella.

Gorgonians produce unusual organic compounds in their tissues, particularly diterpenes, and some of these are important candidates for new drugs. [13] These compounds may be part of the chemical defenses produced by gorgonians to render their tissue distasteful to potential predators. [14] Bottlenose dolphins in the Red Sea have been observed swimming against these tissues, in what is thought to be an attempt to take advantage of the antimicrobial qualities of diterpenes. [15] Despite these chemical defenses, the tissues of gorgonians are prey for flamingo tongue snails of the genus Cyphoma, nudibranchs, the fireworm Hermodice spp., and their polyps are food for butterflyfishes. [16] Amongst the nudibranchs which feed on soft corals and sea fans are the Tritoniidae and the genus Phyllodesmium which specialises in eating Xenia species. [17]

Suborders and families

The World Register of Marine Species lists these suborders and families: [18]

Related Research Articles

<span class="mw-page-title-main">Anthozoa</span> Class of cnidarians without a medusa stage

Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. Sea anemones are mostly solitary, but the majority of corals are colonial, being formed by the budding of new polyps from an original, founding individual. Colonies are strengthened by calcium carbonate and other materials and take various massive, plate-like, bushy or leafy forms.

<i>Isis hippuris</i> Species of coral

Isis hippuris, also known as sea bamboo, is a species of bamboo coral found in the Western Pacific Ocean, commonly near the coasts of Indonesia. I. hippuris reproduce asexually, and is abundant throughout its habitats in Indonesia. For centuries, I. hippuris has been identified by its bamboo or bony-looking structure. Additionally, it is notable for producing Hippuristanol, a molecule that could potentially have anti-cancer applications. While no actual conclusion regarding Hippuristanol in I. hippuris has been published, scientists and marine biologists continue to study how the molecule could be used in cancer research and recovery. Although only found in the Western Pacific Ocean, I. hippuris is highly sought after across the globe, and is seen as a symbol of beauty.

<span class="mw-page-title-main">Octocorallia</span> Class of Anthozoa with 8-fold symmetry

Octocorallia is a class of Anthozoa comprising over 3,000 species of marine organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians within three orders: Alcyonacea, Helioporacea, and Pennatulacea. These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries. As with all Cnidarians these organisms have a complex life cycle including a motile phase when they are considered plankton and later characteristic sessile phase.

<span class="mw-page-title-main">Alcyoniidae</span> Family of corals

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

<span class="mw-page-title-main">Holaxonia</span> Suborder of corals

Holaxonia is a suborder of soft corals, a member of the phylum Cnidaria. Members of this suborder are sometimes known as gorgonians and include the sea blades, the sea fans, the sea rods and the sea whips. These soft corals are colonial, sessile organisms and are generally tree-like in structure. They do not have a hard skeleton composed of calcium carbonate but have a firm but pliable, central axial skeleton composed of a fibrous protein called gorgonin embedded in a tissue matrix, the coenenchyme. In some genera this is permeated with a calcareous substance in the form of fused spicules. Members of this suborder are characterized by having an unspiculated axis and often a soft, chambered central core. The polyps have eight-fold symmetry and in many species, especially in the families Gorgoniidae and Plexauridae, contain symbiotic photosynthetic algae called zooxanthellae. These soft corals are popular in salt water aquaria.

<i>Melithaea ochracea</i> Species of coral

Melithaea ochracea is a species of colonial soft coral in the family Melithaeidae, commonly known as knotted fan coral. It grows in tree-like fans on coral reefs in the South China Sea. It is used in the jewellery industry under the name red spongy coral.

<i>Leptogorgia hebes</i> Species of coral

Leptogorgia hebes, commonly known as the regal sea fan or false sea fan, is a species of soft coral in the family Gorgoniidae. It was formerly included in the genus Lophogorgia but that genus has been dismantled.

<i>Primnoa</i> Genus of corals

Primnoa(Lamororux, 1812) also known as red tree coral, is a genus of soft corals and the type genus of the family Primnoidae (Milne Edwards, 1857). They are sessile, benthic cnidarians that can be found in the North Pacific, North Atlantic, and Subantarctic South Pacific, and its members often play a vital ecological role as keystone species within their environment as a habitat and refuge for the megafauna that also inhabit those regions. This, in combination with their slow growth, makes the increasing disturbance to their habitats caused by fishing activities particularly impactful and difficult to recover from.

<span class="mw-page-title-main">Stolonifera</span> Suborder of soft corals in the order Alcyonacea

Stolonifera is a suborder of soft corals in the order Alcyonacea. Members of this taxon are characterised by having separate polyps budding off an encrusting horizontal, branching stolon. The skeletons include spicules or consists of a horny external cuticle. These soft corals are found in shallow tropical and temperate seas.

<span class="mw-page-title-main">Plexauridae</span> Family of corals

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.

<i>Plexaurella nutans</i> Species of coral

Plexaurella nutans, the giant slit-pore sea rod, is a tall species of soft coral in the family Plexauridae. It is a relatively uncommon species and is found in shallow seas in the Caribbean region.

<i>Eunicea</i> Genus of corals

Eunicea is a genus of gorgonian-type octocorals in the family Plexauridae. These branched octocorals typically have knobby protuberances from which the polyps protrude. They are often stiffened by purple sclerites and some colonies, in brightly lit back-reef areas are purple, though most colonies are brown or grey. The polyps in some species are large and feathery in appearance. The growth of these corals is rapid and they can be kept in a reef aquarium.

<i>Paramuricea clavata</i> Species of coral

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 species was first described by the French naturalist Antoine Risso in 1826.

<i>Alcyonium coralloides</i> Species of coral

Alcyonium coralloides, commonly known as false coral, is a colonial species of soft coral in the family Alcyoniidae. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea. In the former location it generally grows as sheets or small lobes but in the latter it is parasitic and overgrows sea fans.

<i>Antillogorgia bipinnata</i> Species of coral

Antillogorgia bipinnata, the bipinnate sea plume, is a species of colonial soft coral, a sea fan in the family Gorgoniidae. It is found in the Caribbean Sea. It was first described as Pseudopterogorgia bipinnata in 1864 by the American zoologist Addison Emery Verrill. Williams and Chen (2012), transferred all the Atlantic species of Pseudopterogorgia to Antillogorgia.

Taiaroa is a genus of deep-water, solitary marine octocorals in the family Taiaroidae. Taiaroa is monotypic in the family Taiaroidae and contains a single species, Taiaroa tauhou. The species was first described by the marine zoologists Frederick M. Bayer and Katherine Margaret Muzik in 1976. The scientific name derives from "Taiaroa", the submarine canyon off New Zealand in which the first specimens were found and "tauhou", the Maori word for "strange".

Pseudoplexaura porosa, commonly known as the porous sea rod or the porous false plexaura, is a species of gorgonian-type colonial octocoral in the family Plexauridae. It is native to the Caribbean Sea and the Gulf of Mexico.

<span class="mw-page-title-main">Clavulariidae</span> Family of corals

Clavulariidae is a family of soft corals in the suborder Stolonifera. Colonies in this family consist of separate retractable polyps growing from a horizontal, encrusting stolon or basal membrane. The tissues are stiffened by sclerites.

<i>Clavularia crassa</i> Species of coral

Clavularia crassa is a species of colonial soft coral in the family Clavulariidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea. It was first described in 1848 by the French zoologist Henri Milne-Edwards from a specimen collected off the coast of Algeria.

<i>Briareum asbestinum</i> Species of coral

Briareum asbestinum, commonly known as the corky sea finger, is a species of a soft coral in the family Briareidae. It inhabits coral reefs and rocky bottoms in the Caribbean, Bahamas, and Florida, often growing to 30 cm at depths of one to 40 metres.

References

  1. ↑ van Ofwegen, L. (2011). "Alcyonacea Lamouroux, 1812". WoRMS. World Register of Marine Species . Retrieved 15 December 2011.
  2. ↑ Bayer, F. M. (1961). The shallow-water Octocorallia of the West Indian region. Studies on the Fauna of Curaçao and other Caribbean Islands, 12(1), 1-373.; Córdova-Isaza, A., Jiménez-Mármol, S., Guerra, Y., & Salas-Sarduy, E. (2023). Enzyme Inhibitors from Gorgonians and Soft Corals. Marine Drugs, 21(2), 104. https://doi.org/10.3390/md21020104; Raimundo, I., Silva, S., Costa, R., & Keller-Costa, T. (2018). Bioactive Secondary Metabolites from Octocoral-Associated Microbes—New Chances for Blue Growth. Marine Drugs, 16(12), 485. https://doi.org/10.3390/md16120485
  3. ↑ Daly, M., M.R. Brugler, P. Cartwright, A.G. Collins, M.N. Dawson, D.G. Fautin, S.C. France, C.S. McFadden, D.M. Opresko, E. Rodriquez, S.L. Romano, J.L. Stake. (2007). The phylum Cnidaria: A review of phylogenetic patterns and diversity 300 years after Linnaeus. Zootaxa. (1668): 127–182., available online at http://www.mapress.com/zootaxa/2007f/zt01668p182.pdf; McFadden, C.S.; van Ofwegen, L.P.; Quattrini, A.M. (2022) Revisionary systematics of Octocorallia (Cnidaria: Anthozoa) guided by phylogenomics. Bulletin of the Society of Systematic Biologists. 1(3), 8735, pp. 1-79. Available online at https://ssbbulletin.org/index.php/bssb/article/view/8735 page(s): 21; Schoch CL, et al. NCBI Taxonomy: a comprehensive update on curation, resources and tools. Database (Oxford). 2020: baaa062. PubMed: 32761142 PMC: PMC7408187.
  4. 1 2 3 Borneman, Eric H. (2001). Aquarium Corals: Selection, Husbandry, and Natural History. Neptune City, NJ: T.F.H. Publications. p. 464. ISBN   1-890087-47-5.
  5. ↑ "Sea Fan". University of Delaware Graduate College of Marine Studies. Archived from the original on 17 April 2006. Retrieved 23 September 2007.
  6. 1 2 Goldstein, Robert J. (1997). Marine Reef Aquarium Handbook . Barron's Educational Series, Inc. p.  198. ISBN   0-8120-9598-7.
  7. ↑ Heikoop, J.M.; M.J. Risk; C.K. Shearer; V. Atudorei (March 2002). "Potential climate signals from the deep-sea gorgonian coral Primnoa resedaeformis". Hydrobiologia . 471 (1–3): 117–124. doi:10.1023/A:1016505421115. S2CID   7432164.
  8. ↑ Sherwood, Owen A.; Jeffrey M. Heikoop; Daniel J. Sinclair; David B. Scott; Michael J. Risk; Chip Shearer; Kumiko Azetsu-Scott (2005). Cold-Water Corals and Ecosystems. Erlangen Earth Conference Series. Springer Berlin Heidelberg. pp. 1061–1079. doi:10.1007/3-540-27673-4. ISBN   978-3-540-24136-2.
  9. ↑ Bond, Zoë A.; Anne L. Cohen; Struan R. Smith; William J. Jenkins (31 August 2005). "Growth and composition of high-Mg calcite in the skeleton of a Bermudian gorgonian (Plexaurella dichotoma): Potential for paleothermometry". Geochemistry, Geophysics, Geosystems. 6 (8): Q08010. Bibcode:2005GGG.....6.8010B. doi:10.1029/2005GC000911. hdl: 1912/396 . S2CID   128703481.
  10. ↑ Kenji Konishi, "Alcyonarian spiculite: the limestone of soft corals", 1981; M.-S. Jeng, H.-D. Huang, C.-F. Dai, Y.-C. Hsiao and Y. Benayahu. (15 May 2011), "Sclerite calcification and reef-building in the fleshy octocoral genus Sinularia (Octocorallia: Alcyonacea)", Earth and Environmental Science, Coral Reefs doi : 10.1007/s00338-011-0765-z.
  11. ↑ Haywood, Martyn; Sue Wells (1989). The Manual of Marine Invertebrates . Morris Plains, NJ: Tetra Press:Salamander Books Ltd. p.  208. ISBN   3-89356-033-5.
  12. ↑ Agbayani, Eli (5 June 2007). "Hippocampus bargibanti, Pygmy seahorse". FishBase. Retrieved 22 September 2007.
  13. ↑ Berrue, F; Kerr, RG (2009). "Diterpenes from gorgonian corals". Natural Product Reports. 26 (5): 681–710. doi:10.1039/b821918b. PMID   19387501.
  14. ↑ O'Neal, W; Pawlik, JR (2002). "A reappraisal of the chemical and physical defenses of Caribbean gorgonian corals against predatory fishes". Marine Ecology Progress Series. 240: 117–126. Bibcode:2002MEPS..240..117O. doi: 10.3354/meps240117 .
  15. ↑ Attenborough, David (12 November 2017). ""Coral Reefs"". Blue Planet II. Episode 3. BBC One.
  16. ↑ Pawlik, JR; et al. (1987). "Patterns of chemical defense among Caribbean gorgonian corals - A preliminary survey". Journal of Experimental Marine Biology and Ecology. 108: 55–66. doi:10.1016/0022-0981(87)90130-4.
  17. ↑ García-Matucheski, S. and Muniain, C. (2011). Predation by the nudibranch Tritonia odhneri (Opisthobranchia:Tritoniidae) on octocorals from the South Atlantic Ocean. Marine Biodiversity, 41(2), 287–297.
  18. ↑ "WoRMS - World Register of Marine Species - Alcyonacea". marinespecies.org. Retrieved 22 March 2018.
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