Agassizi’s Sea Fan, Pacifigorgia agassizii
Agassiz’s Sea Fan, Pacifigorgia agassizii. Underwater photographs taken within Bandaras Bay, Puerto Vallarta, Jalisco, July 2026. Photographs and identifications courtesy of Greg Timms, youtube.com/@Coralmaster-divesPuertoVallarta/videos.
Phylogeny: Agassiz’s Sea Fan, Pacifigorgia agassizii (Verrill, 1864), is an octocoral and a member of the Gorgoniidae Family of Gorgonians. The nineteen genera within the Gorgoniidae 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. The Pacifigorgia Genus contains thirty-seven species. This species was named in honor of Louis Agassiz, the American biologist, glaciologist, and geologist. Agassiz was know as the Father of the Ice Age. Seventeen species are named in his honor. It is known in Mexico as Abanico de Agassiz.
Morphology: Agassiz’s Sea Fans may grow as one or two fan-shaped planes with a mesh-like structure. The skeleton is thin, reaching only 1.1 mm (0.043 inches) in diameter. The skeleton is covered with coenenchyme (living tissue that connects the polyps). The eight tentacled polyps are arranged in longitudinal rows along the branches. When disturbed, the polyps retract into flat, or slightly raised, oval rings. They are generally greenish-brown or greenish-gray in color. The polyps may be orangish-beige or olive-green. Agassiz’s Sea Fans can grow to 40 cm (2 feet 6 inches) in height and width.
Habitat and Distribution: Agassiz’s Sea Fans are found on hard substrates such as rocks, coral, and wreckage. They are one of the least studied and documented octocoral species in the region. Regarding the depth range for this species has not been formally documented. They are generally found at depths between 2 m (6.5 feet) to 25 m (82 feet). Agassiz’s Sea Fans is a Tropical Eastern Pacific species that is found in all Mexican waters of the Pacific Ocean, with the exception that they are absent from the west coast of the Baja Peninsula and north of La Paz, Baja California Sur, in the Sea of Cortez. Interestingly, the Encyclopedia of Life shows one record from the Santa Barbara Museum of Natural History of the Agassiz’s Sea Fan being found on the northwest coast of the Baja Peninsula, near Puerto San Isidro, Baja California. Perhaps this was based on a misidentification, a waif specimen, or a specimen introduced to the area.
Diet: Agassiz’s Sea Fans are sessile suspension feeders that depend on water movement to bring them food, such as amphipods, fish larvae, and other plankton.
Predators: The predation of Agassiz’s Sea Fans has not been formally documented. Similar species in the Pacifigorgia Genus are preyed upon by fish, gastropods, nudibranchs, and sea stars.
Reproduction: Agassiz’s Sea Fans are gonochoric (male or female for life). They reproduce sexually through broadcast spawning with external fertilization. The fertilized eggs develop into planktonic planular larvae. The larvae drift until they find suitable habitat and settle to the substrate. There, the coral asexually clones itself, through budding, to grow a new colony. They can also reproduce asexually through fragmentation and by sending out runners (stolonization).
Ecosystem Interactions: Agassiz’s Sea Fans are known to host bacteria, ciliates, parasitic fungi, and other micro-parasites. Larger parasites, such as zoanthids, can attach to the sea fan, overgrowing and suffocating the tissue. Amphipods, brittle stars, copepods, crabs and shrimp find camouflage, shelter and elevating structure within the branches of this sea fan.
Human Interactions: Agassiz’s Sea Fans have a very limited impact on human activities. They are occasionally collected for the curio and aquarium trade. From a conservation perspective they have not been formally evaluated.
Synonyms: Gorgonia (Litigorgia) agassizii, Gorgonia agassizii, Leptogorgia agassizi, Leptogorgia agassizii, Litigorgia agassizii, Rhipidigorgia agassizii, and Rhipidogorgia agassizii .