Gorgonians of the Gorgoniidae Family
Phylogeny: Gorgonians are an octocoral that are members of the Gorgoniidae Family and like hydroids, jellyfish and sea anemones they belong to the Phylum Cnidaria. They are the Class Anthozoa, the Sub-class Octocorallia or Octocoral that are also known as Alcyonaria, and the Order Alcyonacea.
Distribution: Gorgonians are are found worldwide being the most prominent tropical corals found along both coasts of the Americas where they are more prolific than in any other global location. There are two hundred and fifty species in the Gorgoniidae Family of which thirty are found along the Pacific Coast of Mexico. Most Gorgonians 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.
Morphology: The Octocorals lack the hard calcium carbonate skeletons of Stony Corals and are often called Soft 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. an eight-fold symmetry with eight pinnate (having a feather-like appearance) tentacles hat include soft corals whose sclerites are less than 0.3 mm in length. They have a radial symmetry, a hollow digestive cavity, and specialized stinging structures in the tentacles that surround the mouth. Their polyps have a flower-like appearance. 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 (the coenenchyme) which surrounds the core. The material surrounding the openings in the coenenchymes (calyx or calyces) is from which the polyps emerge. 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 that have hollow axial cores which lack scierites with the scierties found within the coenechyme.
Ecosystem Roles: The 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. Soft 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.