Gorgoniidae Family of Soft Corals

Ten Gorgonians of the Gorgoiniidae Family can be found in this website:

Phylogeny: Gorgonians are an octocoral that are members of the Gorgoniidae Family of Soft Corals and like hydroids, jellyfish and sea anemones they belong to the Cnidaria Phylum. They are the Subphylum Anthozoa, the Class Octocorallia, and the  Malacalcyonacea Order. The Gorgoniidae Family is one of forty-nine families in this order. The Gorgoniidae Family contains thirteen genera and two hundred nine species. The genera within this family are separated by the degree and type of spiculation, along with the pattern of branching and the morphology of the colony as a whole.

Morphology: As octocorals, Gorgonians 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. The sclerites are less than 0.3 mm in length. The polyps have eight-fold radial symmetry, with eight pinnate (having a feather-like appearance) tentacles. The polyps have a hollow digestive cavity, and specialized stinging structures in the tentacles that surround the mouth. Their polyps have a flower-like appearance. The central core  of the branches is composed of a horn-like substance called gorgonin. Gorgonin is comprised of bromine and iodine, with a protein that is exclusive to 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 polyps may be flush with the surface or raised, with just the tentacles and mouth exposed. Gorgonian colonies may be whip-like, rod-like, bushy or fan-shaped.  Species in this family range in size from 15 cm (6 inches) to sea fans over 1.80 m (6 feet) tall and 1.5 m (5 feet) wide. Gorgonians in the Gorgoniidae Family differ from those in the Plexauridae Family, which have hollow axial cores, with the sclerites found within the coenechyme.

Given the complexity of sorting species within this family, especially for field identification, it is helpful to group similar looking species as follows:

Branches are thick, wide, or flattened. Junctions are heavily webbed, making the fan look like a solid plate with holes cleanly punched out.

Group 3: The Fringed, Speckled & Intermediate Mesh Group (Open Perimeter / Distinct Grids)

Dense or intermediate grids distinguished by open edges failing to close, bright color mottling, or highly geometric square-to-rectangular holes.

Distribution: Gorgonians are found attached to hard surfaces including corals, mudstones, pilings, rocks and wreckage. 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). Gorgonians are found worldwide in temperate to tropical seas. They are the most prominent corals found along both coasts of the Americas where they are more prolific than in any other global location. There are at least thirty-two species from this family in Mexican waters.

Reproduction: Gorgonians colonies are gonochoric (male or female). Reproduction may be asexual, through fragmentation. When a piece of branch is broken away from the colony, and lands in a suitable habitat, it can start growing a new colony. Reproduction can also be sexual. Sexual reproduction is accomplished through broadcast spawning, with external fertilization. The gametes are shed into the coelenteron and spawned through the mouth. The zygote develops into a planktonic planula larva. Metamorphosis begins with early morphogenesis of tentacles, septa and pharynx before larval settlement on the aboral end.

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.

Gorgonians have a very limited impact on human activities. Their shallow-water habitat  may increase its exposure to anthropogenic stressors associated with declining coastal water quality. Pollution, sedimentation, and nutrient enrichment from terrestrial runoff can promote the proliferation of algae and cyanobacteria, including filamentous forms that may become entrained within the branching structure of colonies. Accumulation of such growth may reduce water circulation around the colony and interfere with feeding, while persistent overgrowth has the potential to cause physical abrasion, smother living tissue, and contribute to tissue loss or colony decline. Similar effects associated with algal and cyanobacterial overgrowth have been documented in other gorgonian corals, suggesting that these interactions may represent a potential ecological stressor for the Gorgonians. However, the prevalence, severity, and conservation implications of algal and cyanobacterial overgrowth in Gorgonians has not been formally assessed.