page_title: Alcyonacea
section_title: Anatomy
hierarchical_section_title: Alcyonacea / Anatomy
caption_attribution_description: Leather coral (Alcyoniidae)
context_page_description: Alcyonacea, or soft corals, are an order of corals that do not produce calcium carbonate skeletons. Formerly known as gorgonians, they are sessile colonial cnidarians found throughout the oceans of the world, especially in the tropics and subtropics. Common names for subset of this order are sea fans and sea whips; they 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, Bermuda, and the West Indies.
context_section_description: 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. Most of the Holaxonia and Scleraxonia, however, do not attach themselves to a hard substrate. Instead, they anchor themselves in mud or sand.
  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.
caption: A close-up of an alcyonacean showing individual polyps
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