Sea fan
| Gorgonian | |
|---|---|
 |
|
| Iciligorgia schrammi | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Anthozoa |
| Subclass: | |
| Order: |
Alcyonacea Lamouroux, 1812 |
| Suborders and families | |
Alcyonacea is an order of sessile colonial cnidarians found throughout the oceans of the world, especially in the tropics and subtropics. The name "Gorgonacea" is no longer considered valid and Alcyonacea is now the accepted name for the order. Gorgonians are also known as sea whips and sea fans and are similar to the sea pen, a soft coral. Gorgonians are closely related to coral. 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 reef aquariums.
Gorgonians are classified in the phylum Cnidaria, class Anthozoa, alongside the orders Alcyonacea (soft corals) and Pennatulacea (sea pens). There are about 500 different species of gorgonians 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.
The structure of a gorgonian colony varies. In the suborder Holaxonia, skeletons are formed from a flexible, horny substance called gorgonin. The suborder Scleraxonia variety of gorgonians are supported by a skeleton of tightly grouped calcareous spicules. There are also species which encrust like coral. Most of Holaxonia and Sclerazonia, however, do not attach themselves to a hard substrate. Instead, they anchor themselves in mud or sand.
Research has shown that measurements of the gorgonin and calcite within several long-lived species of gorgonians can be useful in paleoclimatology and paleoceanography, as the skeletal growth rate and composition of these species is highly correlated with seasonal and climatic variation.
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