G. ventalina is a fan-shaped colonial coral with several main branches and a latticework of linking smaller branches. The skeleton is composed of calcite and gorgonion, a collagen-like compound. The calyces in which the polyps are embedded are in two rows along the branches. Many of the smaller branches are compressed in the plane of the fan, which distinguishes this species from the Venus sea fan (Gorgonia flabellum). It often has small accessory fans growing out sideways from the main fan. It grows to 1.5 m (5 ft) tall and is variable in colour, being whitish, yellow, or pale purple. The main branches are often purple and the fan is orientated at right angles to the current. The skeleton of G. ventalina contains hard structures known as sclerites which are unpalatable to predators. It also contains certain secondary metabolites in its tissues which are distasteful. The nudibranch Tritonia hamnerorum seems undeterred by these defences and is often found associated with the coral. While feeding on the coral, it concentrates the metabolites in its tissues which render it unpleasant to potential predators. Learn more about Common Sea Fan