Octocorallia

Image:Tubipora01.jpg of Tubipora musica.]]

Octocorals resemble the stony corals in general appearance and in the size of their polyps, but lack the distinctive stony skeleton. Also unlike the stony corals, each polyp has only eight tentacles, each of which is feather-like in shape, with numerous side-branches, or pinnules.

Octocorals are colonial organisms, with numerous tiny polyps embedded in a soft matrix that forms the visible structure of the colony. The matrix is composed of mesogleal tissue, lined by a continuous epidermis and perforated by numerous tiny channels. The channels interconnect the gastrovascular cavities of the polyps, allowing water and nutrients to flow freely between all the members of the colony. The skeletal material, called coenenchyme, is composed of living tissue secreted by numerous wandering amoebocytes. Although it is generally soft, in many species it is reinforced with calcareous or horny material.{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|pages= 164–169|isbn= 0-03-056747-5}}

The polyp is largely embedded within the colonial skeleton, with only the uppermost surface, including the tentacles and mouth, projecting about the surface. The mouth is slit-like, with a single ciliated groove, or siphonoglyph, at one side to help control water flow. It opens into a tubular pharynx that projects down into a gastrovascular cavity that occupies the hollow interior. The pharynx is surrounded by eight radial partitions, or mesenteries, that divide the upper part of the gastrovascular cavity into chambers, one of which connects to the hollow space inside each tentacle. The gonads are located near the base of each mesentery. Octocorals have high phenotypic plasticity from adapting to dynamic environments where temperature, pH, and other parameters are in constant flux{{Cite journal |last1=Lopes |first1=Ana Rita |last2=Faleiro |first2=Filipa |last3=Rosa |first3=Inês C. |last4=Pimentel |first4=Marta S. |last5=Trubenbach |first5=Katja |last6=Repolho |first6=Tiago |last7=Diniz |first7=Mário |last8=Rosa |first8=Rui |date=2018-06-11 |title=Physiological resilience of a temperate soft coral to ocean warming and acidification |journal=Cell Stress and Chaperones |volume=23 |issue=5 |pages=1093–1100 |doi=10.1007/s12192-018-0919-9 |issn=1355-8145|doi-access=free |pmid=29948929 |pmc=6111073 }} and have shown high recruitment rates post-die-off events caused by El Niño events.{{Cite journal |last1=Lasker |first1=H. R. |last2=Martínez-Quintana |first2=Á. |last3=Bramanti |first3=L. |last4=Edmunds |first4=P. J. |date=2020-03-09 |title=Resilience of Octocoral Forests to Catastrophic Storms |journal=Scientific Reports |volume=10 |issue=1 |page=4286 |doi=10.1038/s41598-020-61238-1 |issn=2045-2322|doi-access=free |pmid=32152448 |pmc=7063042 |bibcode=2020NatSR..10.4286L }}

Bioluminescence is found in 32 genera, a trait estimated to have evolved 540 million years ago, the earliest timing of emergence of bioluminescence in the marine environment.{{cite journal|doi=10.1098/rspb.2023.2626 |title=Evolution of bioluminescence in Anthozoa with emphasis on Octocorallia |date=2024 |last1=Deleo |first1=Danielle M. |last2=Bessho-Uehara |first2=Manabu |last3=Haddock |first3=Steven H.D. |last4=McFadden |first4=Catherine S. |last5=Quattrini |first5=Andrea M. |journal=Proceedings of the Royal Society B: Biological Sciences |volume=291 |issue=2021 |pmid=38654652 |pmc=11040251 }}

Octocorallia is considered to be monophyletic, meaning that all contained species are descended from a common ancestor, but the relationships between subdivisions are not well known. The sea pens (Pennatulacea) and blue coral (Helioporacea) continue to be assigned separate orders, whereas the current order Alcyonacea was historically represented by four orders: Alcyonacea, Gorgonacea, Stolonifera and Telestacea.

The following taxa are unplaced within Octocorallia according to the World Register of Marine Species {{As of|2024|April|lc=y}}:{{cite WoRMS|title=Octocorallia incertae sedis|id=151642|accessdate=23 April 2024}}

Families:

• Haimeidae {{small|Wright, 1865}}
• Pseudogorgiidae {{small|Utinomi & Harada, 1973}}

Genera:

• Aspera {{small|Dautova, 2018}}
• Bayergorgia {{small|Williams & López-González, 2005}}
• Briareopsis {{small|Bayer, 1993}}
• Caliacis {{small|Deichmann, 1936}}
• Canarya {{small|Ocaña & van Ofwegen, 2003}}
• Ceratocaulon {{small|Jungersen, 1892}}
• Chalcogorgia {{small|Bayer, 1949}}
• Chondronephthya {{small|Utinomi, 1960}}
• Daniela {{small|von Koch, 1891}}
• Denhartogia {{small|Ocaña & van Ofwegen, 2003}}
• Distichogorgia {{small|Bayer, 1979}}
• Elasmogorgia {{small|Wright & Studer, 1889}}
• Flagelligorgia {{small|Cairns & Cordeiro, 2017}}
• Hypnogorgia {{small|Duchassaing & Michelotti, 1864}}
• Inflatocalyx {{small|Verseveldt & Bayer, 1988}}
• Lanthanocephalus {{small|Williams & Starmer, 2000}}
• Lignopsis {{small|Pérez & Zamponi, 2000}}
• Mesogligorgia {{small|López-González, 2007}}
• Moolabalia {{small|Alderslade, 2001}}
• Pseudocladochonus {{small|Versluys, 1907}}
• Pseudosuberia {{small|Kükenthal, 1916}}
• Pseudothesea {{small|Kükenthal, 1919}}
• Rhipiopathes
• Rolandia {{small|de Lacaze-Duthiers, 1900}}
• Scleranthelia {{small|Studer, 1878}}
• Speirogorgia {{small|Williams, 2019}}
• Sphaeralcyon {{small|López-González & Gili, 2000}}
• Stereacanthia {{small|Thomson & Henderson, 1906}}
• Stereogorgia {{small|Kükenthal, 1916}}
• Stereosoma {{small|Hickson, 1894}}
• Tesseranthelia {{small|Bayer, 1981}}
• Thelogorgia {{small|Bayer, 1991}}
• Tubigorgia {{small|Pasternak, 1985}}
• Verseveldtia {{small|Williams, 1990}}
• Williamsium {{small|Moore, Alderslade & Miller, 2017}}
• Xenogorgia {{small|Bayer & Muzik, 1976}}

{{Reflist}}

{{Commons category|Octocorallia}}

{{Wikispecies|Alcyonaria}}

• {{ITIS |id=52004 |taxon=Octocorallia}}

{{Taxonbar|from=Q132680}}

{{Authority control}}

Category:Anthozoa

Category:Animal classes