Dendrogyra cylindrus (Ehrenberg, 1834) - pillar coral on a patch reef. (photo taken by Mark Peter)

Stony corals have a patchy distribution in the shallow marine waters surrounding San Salvador Island. They occur as isolated individual colonies, in patch reefs, fringing reefs, and barrier reefs. Stony corals are scleractinian anthozoan cnidarians (there are also non-scleractinian stony corals in the fossil record, such as tabulates and rugosans). They consist of individuals or colonies of gelatinous polyps that secrete hard skeletons of aragonite (CaCO3). Most scleractinian corals live in warm, tropical to subtropical, photic zone environments (the shallow portions of the world’s oceans where sunlight penetrates). Microbes (Symbiodinium - Protista, Dinoflagellata/Pyrrhophyta) called zooxanthellae live in their tissues and need to be in sunlight to make their own food (photosynthesis), which is shared with the host coral animal. Scleractinian corals have stinging cells (nematocysts) in their tentacles that paralyze prey.

Pillar corals have skeletons of numerous, upright, subcylindrical structures. The large blue fish in the above photo is a blue tang (Acanthurus coeruleus). The small blue-black-white-yellow fish is a bluehead wrasse (Thalassoma bifasciatum). The purplish-colored seafan at lower right is Gorgonia ventalina. The small, light-brown, branching coral below the purple seafan is a branching fire coral (Millepora alcicornis).

Classification: Animalia, Cnidaria, Anthozoa, Scleractinia, Meandrinidae