# Holaxonia

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.

## Families and genera

The World Register of Marine Species list the following families and genera:
* Family Acanthogorgiidae Gray, 1859
** Genus Acanthogorgia Gray, 1857
** Genus Anthogorgia Verrill, 1868
** Genus Calcigorgia Broch, 1935
** Genus Calicogorgia Thomson & Henderson, 1906
** Genus Callicigorgia
** Genus Cyclomuricea Nutting, 1908
** Genus Muricella Verrill, 1868
** Genus Versluysia Nutting, 1910
* Family Dendrobrachiidae Brook, 1889
** Genus Dendrobrachia Brook, 1889
* Family Gorgoniidae Lamouroux, 1812
** Genus Adelogorgia Bayer, 1958
** Genus Antillogorgia Bayer, 1951
** Genus Eugorgia Verrill, 1868
** Genus Eunicella Verrill, 1869
** Genus Filigorgia Stiasny, 1937
** Genus Gorgonia Linnaeus, 1758
** Genus Guaiagorgia Grasshoff & Alderslade, 1997
** Genus Hicksonella Nutting, 1910
** Genus Leptogorgia Milne-Edwards, 1857
** Genus Olindagorgia Bayer, 1981
** Genus Pacifigorgia Bayer, 1951
** Genus Phycogorgia Milne Edwards & Haime, 1850
** Genus Phyllogorgia Milne Edwards & Haime, 1850
** Genus Pinnigorgia Grasshoff & Alderslade, 1997
** Genus Pseudopterogorgia Kükenthal, 1919
** Genus Pterogorgia Ehrenberg, 1834
** Genus Rumphella Bayer, 1955
** Genus Tobagogorgia Sanchez, 2007
* Family Keroeididae Kinoshita, 1910
** Genus Ideogorgia Bayer, 1981
** Genus Keroeides Studer, 1887
** Genus Lignella Gray, 1870
** Genus Pseudothelogorgia (van Ofwegen, 1990)
** Genus Thelogorgia Bayer, 1991
* Family Plexauridae Gray, 1859
** Genus Acanthacis Deichmann, 1936
** Genus Acanthomuricea Hentschel, 1903
** Genus Acis Duchassaing & Michelotti, 1860
** Genus Alaskagorgia Sánchez & Cairns, 2004
** Genus Anthomuricea Studer, 1887
** Genus Anthoplexaura Kükenthal, 1908
** Genus Astrogorgia Verrill, 1868
** Genus Astromuricea Germanos, 1895
** Genus Bayergorgia Williams & Lopez-Gonzalez, 2005
** Genus Bebryce Philippi, 1841
** Genus Chromoplexaura Williams, 2013
** Genus Cryogorgia Williams, 2005
** Genus Dentomuricea Grasshoff, 1977
** Genus Discogorgia Kükenthal, 1919
** Genus Echinogorgia Kölliker, 1865
** Genus Echinomuricea Verrill, 1869
** Genus Elasmogorgia Wright & Studer, 1889
** Genus Eunicea Lamouroux, 1816
** Genus Euplexaura Verrill, 1869
** Genus Heterogorgia Verrill, 1868
** Genus Hypnogorgia Duchassaing & Michelotti, 1864
** Genus Lapidogorgia Grasshoff, 1999
** Genus Lepidomuricea Kükenthal, 1919
** Genus Lytreia Bayer, 1981
** Genus Menacella Gray, 1870
** Genus Menella Gray, 1870
** Genus Mesogligorgia Lopez-Gonzalez, 2007
** Genus Muricea Lamouroux, 1821
** Genus Muriceides Wright & Studer, 1889
** Genus Muriceopsis Aurivillius, 1931
** Genus Paracis Kükenthal, 1919
** Genus Paramuricea Koelliker, 1865
** Genus Paraplexaura Kükenthal, 1909
** Genus Placogorgia Wright & Studer, 1889
** Genus Plexaura Lamouroux, 1821
** Genus Plexaurella Kölliker, 1865
** Genus Plexauroides Wright & Studer
** Genus Plexauropsis Verrill
** Genus Psammogorgia Verrill, 1868
** Genus Pseudoplexaura Wright & Studer, 1889
** Genus Pseudothesea Kükenthal, 1919
** Genus Scleracis Kükenthal, 1919
** Genus Spinimuricea Grasshoff, 1992
** Genus Swiftia Duchassaing & Michelotti, 1864
** Genus Thesea Duchassaing & Michelotti, 1860
** Genus Trimuricea Gordon, 1926
** Genus Villogorgia Duchassaing & Michelloti, 1862