Gorgonia ventalina

Lore & Background

Gorgonia ventalina forms a fan-shaped colonial coral with several main branches and a latticework of linking smaller branches. Its skeleton is composed of calcite and gorgonin, a collagen-like compound. The calyces containing the polyps are arranged in two rows along the branches, and many smaller branches are compressed in the plane of the fan, distinguishing it from the Venus sea fan (Gorgonia flabellum). It often has small accessory fans growing sideways from the main fan. The fan is orientated at right angles to the current, and its color varies from whitish, yellow, or pale purple, with main branches often purple.

This species is a filter feeder; each polyp extends eight tentacles to catch plankton drifting on the current. Its tissues contain symbiotic dinoflagellates of the genus Symbiodinium, which are photosynthetic and provide organic carbon compounds to the host. The skeleton contains hard sclerites that are unpalatable to predators, and its tissues also contain distasteful secondary metabolites. The nudibranch Tritonia hamnerorum is often found associated with the coral, feeding on it and sequestering the chemical compound julieannfuran from G. ventalina to use as a chemical deterrent against predators.

The coral is sometimes attacked by the fungus Aspergillus sydowii, causing aspergillosis with damaged patches, galls, purpling of tissues, and even death. Epizootics have occurred in the Caribbean on corals in stressful conditions such as low-salinity water in estuaries. A parasite of the class Labyrinthulomycetes in the family Thraustochytriidae has been found to cause similar damaged purple patches called multifocal purple spots. A study in the U.S. Virgin Islands showed that G. ventalina has high ecological resilience, maintaining its densities after two hurricanes in 2017.

Reader's Guide

Gorgonia ventalina is a significant component of western Atlantic and Caribbean reef communities, serving as a filter feeder that captures plankton from passing currents. Its symbiotic relationship with photosynthetic dinoflagellates (Symbiodinium spp.) links it to primary production in shallow waters. The species exhibits chemical and structural defenses against predation, including unpalatable sclerites and secondary metabolites, which are exploited by the nudibranch Tritonia hamnerorum that sequesters the compound julieannfuran for its own protection. The coral is vulnerable to disease, notably aspergillosis caused by the fungus Aspergillus sydowii, which has led to epizootics in stressful environments such as low-salinity estuaries. Additionally, a Labyrinthulomycetes parasite produces similar purple lesions. Despite these threats, a study in the U.S. Virgin Islands demonstrated high ecological resilience, with populations maintaining densities after two hurricanes. The species' fan-shaped morphology, orientation perpendicular to currents, and variable coloration (whitish, yellow, or pale purple) are key identifying features, with the compressed smaller branches distinguishing it from Gorgonia flabellum. Its distribution spans from Bermuda and Florida through the Gulf of Mexico to Curaçao, in shallow waters with strong wave action or deeper outer reefs with strong currents down to about 15 meters.

Did You Know?

• Gorgonia ventalina grows to 1.5 m (5 ft) tall and is variable in color, being whitish, yellow, or pale purple.
• The nudibranch Tritonia hamnerorum sequesters the chemical compound julieannfuran from G. ventalina to deter predators.