Gorgonians are a group of colonial cnidarians belonging to the order Malacalcyonacea, within the octocorals. They are characterized by forming arborescent or fan-shaped colonies supported by a flexible axial skeleton composed of a protein called gorgonin, sometimes reinforced with calcium carbonate deposits. This structure allows them to sway with currents without breaking, a key adaptation for life in exposed environments. Their polyps, with eight pinnate tentacles, are distributed along the branches and act in coordination to capture food. Around 1,200 species of gorgonians have been described, distributed globally, with the highest diversity in tropical and subtropical regions, though representatives also exist in temperate and deep waters.
Morphologically, gorgonians exhibit great variability in shape, size, and coloration. Colonies can grow as flat fans oriented perpendicular to currents, three-dimensional bushy structures, or slender whips extending into the water column. Some species are just a few centimeters tall, while others exceed two meters in height. Their coloration depends on both intrinsic pigments and the presence of symbionts, ranging from yellow and orange to deep red, purple, or even white. Polyps are generally retractile and extend to feed when water flow conditions are optimal.
In terms of feeding, gorgonians are primarily suspension feeders. They capture plankton and organic particles suspended in the water using their tentacles armed with cnidocytes. Many species in shallow waters maintain a symbiotic relationship with photosynthetic algae of the genus Symbiodinium (zooxanthellae), which allows them to supplement their diet with organic compounds produced via photosynthesis. However, in deeper or turbid waters where light does not penetrate, they rely exclusively on heterotrophic feeding, adapting to slower growth rates.
The sub-classification of gorgonians within the order Alcyonacea is organized into several main groups. True gorgonians (Suborder Holaxonia, families such as Gorgoniidae and Plexauridae) include species with a flexible axial skeleton and generally cylindrical branches, abundant in tropical reefs. Calcaxonian gorgonians (Suborder Calcaxonia, families such as Ellisellidae) have a stiffer, partially calcified axis and often form branched colonies in deeper environments. Finally, scleraxonian gorgonians (Suborder Scleraxonia, families such as Anthothelidae) possess an axis composed of aggregated sclerites, giving them greater rigidity and more massive or whip-like forms.
Gorgonians play a fundamental ecological role by providing refuge and settlement surfaces for numerous invertebrates and fish, contributing to the structural complexity of benthic ecosystems. Additionally, they produce secondary metabolites with pharmacological potential, some of which are being studied for their anti-inflammatory and antitumor properties. However, their slow growth and sensitivity to disturbances such as bottom trawling, pollution, and climate change make them a vulnerable group, whose conservation is essential to maintaining marine biodiversity.
