sea fan

any of certain anthozoans, esp. Gorgonia flabellum, of the West Indies, in which the colony assumes a fanlike form.

[1625-35]

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Any of about 500 coral species (genus Gorgonia) especially abundant in shallow waters along the Atlantic coasts of Florida, Bermuda, and the West Indies.

Polyps grow colonially in a flat, fanlike pattern. Each polyp has some multiple of six tentacles, which it spreads out to form a plankton-catching net. An internal skeleton supports all branches of the colony. The living tissues (often red, yellow, or orange) entirely cover the skeleton. The fan-shaped colonies usually grow across the current, increasing their ability to ensnare prey. All species grow to about 2 ft (60 cm) high.

Sea fan

Douglas Faulkner

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▪ invertebrate

 (Gorgonia), any of a genus of invertebrate marine animals of the order Gorgonacea (class Anthozoa, phylum Cnidaria). It is a variety of coral composed of numerous polyps—cylindrical sessile (attached) forms—that grow together in a flat, fanlike pattern. Each polyp in the colony has some multiple of six tentacles, as opposed to the eightfold symmetry of the similar black coral. A central internal skeleton, composed of a flexible, horny substance called gorgonin, supports all branches of the colony, and the living tissues form a layer over its entire surface. The tissues are often coloured in hues of red, yellow, or orange. The polyps spread out their tentacles to form a plankton-catching net. In most cases the fan-shaped colonies grow across the current, which increases their ability to ensnare prey.

      In reproduction, fertilized eggs develop into microscopic ciliated larvae (planulae). Each larva disperses from the parent colony before it metamorphoses in adult form. Each newly metamorphosed polyp eventually gives rise to an entire sea fan colony through asexual budding.

      There are about 500 species of Gorgonia, and they differ markedly in their branching patterns. All, however, grow to approximately 61 cm (2 feet) in height. Sea fans are found in the shallow waters of all oceans, but they are especially abundant along the Atlantic coasts of Florida, Bermuda, and the West Indies.

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