Red Sea Fan, Pacifigorgonia adamsi

Red Sea Fan, Pacifigorgonia adamsi. Sea fans collected in the greater Cabo San Lucas area, Baja California Sur.  A fairly common by-catch of a bottom fisherman.

Red Sea Fan, Pacifigorgonia adamsi. Underwater photographs taken in the greater Cabo San Lucas area, Baja California Sur, March 2018. Photographs courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  The Red Sea Fan, Pacifigorgia adamsi (Verrill, 1868), is an octocoral in the Gorgoniidae family of Gorgonians. The genus Pacifigorgia is one of thirteen genera in this family, and there are thirty-seven species in this genus. 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. They are known in Mexico as Abanico Rojo de Mar.

Morphology: Red Sea Fans are colonial organisms, with polyps that have 8-fold radial symmetry. Their eight tentacles are pinnate (having a feather-like appearance). The polyps have a flower-like appearance, a hollow digestive cavity, and specialized stinging structures in tentacles surrounding the mouth. As octocorals, they have tiny spine-like hard parts in their bodies called sclerites (or spicules) that give them some degree of support. The branches have a central core, which is made of a horn-like substance called gorgonin. Gorgonin is a protein which is exclusive to the gorgonians and which contains significant amounts of iodine and bromine. The sclerites are located in the solid core. 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) are called calyces (singular calyx). The branches are arranged in a fan-shaped plane. The planes are mesh-like in construction, with the spaces in the mesh being about twice as wide as the branches. Red Sea Fans may be rusty-red, brown, or maroon in color with white to yellowish polyps. They reach a maximum of 30 cm (11.7 inches) in height.

Habitat and Distribution: Red Sea Fans are found attached to offshore reefs and rocks, subtidally, and to depths of 35 m (115 feet). They branches are usually oriented to be perpendicular to the prevailing current or surge, to facilitate filter feeding. Red Sea Fans are a tropical Eastern Pacific species. In Mexican waters they are found throughout the Gulf of California and range south to Guatemala, including the Revillagigedos Islands.

Diet: Red Sea Fans are suspension feeders that use their tentacles to capture prey such as amphipods, fish eggs, larvae and other zooplankton. They are azooxanthellate.

Predators:  Red Sea Fans are a poorly studied and understood species. There is very little documentation regarding predation. Other species in this family are prey for fish, gastropods and sea stars.

Reproduction: Red Sea Fans can reproduce asexually through budding and sexually through spawning. During spawning, mass amounts of eggs and sperm are released, through the mouth, into the water and fuse into gametes. The fertilized eggs  hatch into planular larvae, which will eventually settle on a hard substrate and begin to form a polyp. From here, a colony grows through cloning (asexual reproduction).

Ecosystem Interactions: Again, Red Sea Fans are a poorly studied and understood species. There is little documentation of any parasitic, commensal or symbiotic relationships for this species. Other members of this family are known to host parasites including: filamentous algae, parasitic copepods, cyanobacteria, terrestrial fungi, protozoans and viruses.

Human Interactions:  Red Sea Fans have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms:  Gorgonia (Litigorgia) adamsii, Gorgonia adamsii, Leptogorgia adamsii, and Litigorgia adamsii.