Gorgonians of the Gorgoniidae Family
Bumpy Orange Gorgonian, Eurogia aurantica
Gorgonians are an octocoral that are members of the Gorgoniidae Family. Like hydroids, jelly fish and sea anemones they belong to the Phylum Cnidaria as they have radial symmetry, a hollow digestive cavity, and specialized stinging structures in the tentacles that surround the mouth. They are in the Class Anthozoa, with their polyps have a flower-like appearance. They are in the sub-class Octocorallia or Octocoral that are also known as Alcyonaria. The Octocorals are colonial organisms that have eight-fold radial symmetry with eight pinnate (having a feather-like appearance) tentacles. They lack the hard calcium carbonate skeletons of Stony Corals and are often called Sofeet Corals. In place of a hard skeleton, they have tiny spine-like parts in their bodies called sclerites (or spicules) that gives them some level of support. Colonies may be branch-like, bushy, encrusting or fan-like. The Octocorals include the feather plumes, sea fans, sea rods and sea whips.
The Gorgoniidae Family includes soft corals whose sclerites are less than 0.3 mm in length. They are sculptured with regularly disposed girdles of tubercles. The colonies may be bush or fan shaped with the branches having a central core that is composed of a horn-like substance called gorgonin. Gorgonin is a bromine and iodine containing protein that is exclusive to the gorgonians. The sclerites are located in the solid core and the polyps are embedded in a gelatinous material (called the coenenchyme) which surrounds the core. The material surrounding the openings in the coenenchymes (from which the polyps emerge) is called calyx or calyces. They may be flush with the surface of the ocean bed or raised, with just the tentacles and mouth exposed. Gorgonians in the Gorgoniidae Family differ from those in the Plexauridae Family (hollow axial cores which lack scierites with the scierties found within the coenechyme.
Gorgonians originate from planktonic larvae which settle onto a suitable hard surface, attach and become sessile. They are not mobile and water currents to supply them with a constant supply of planktonic food such as amphipods and fish larvae. Sofeet Corals in turn are preyed upon by fish, gastropods and starfish. Some of the nudibranchs that feed on these corals are remarkably camouflaged to blend in with their hosts. Like Hard Corals, some Gorgonians are zooxanthellate that have a symbiotic relationship with single-cell dinoflagellates, a zooxanthellae. Zooxanthellae live within certain coral polyps, jellyfish, nudibranchs and sea anemones. The zooxanthellae produce energy, during daylight, by means of photosynthesis with the energy being passed along to their hosts, sometimes providing up to 90% of the host’s total energy requirements. In return, the host provides carbon dioxide, nutrients, and a secure, sunlit, dwelling for the zooxanthellae.
Gorgonians are the most prominent tropical corals found along both coasts of the Americas. They are found worldwide, in tropical and temperate waters but are more prolific in the Americans that in any other global location. Most are found in shallow waters where there is more sunlight and ample water movement, but some are found at depths exceeding 3,050 m (10,000 feet). They are found attached to hard surfaces including corals, mudstones, pilings, rocks and wreckage. There are 250 species in the Gorgoniidae Family of which 30 are found along the Pacific Coast of Mexico.