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A close-up image of brain coral in the Dry Tortugas, Fla. Brain coral gets its name from the colony’s meandering, brain-like pattern of brown walls, separated by gray or green depressions known as "valleys." Each head of coral is formed by a colony of genetically identical polyps, which secrete a hard skeleton of calcium carbonate.
Brain corals extend their tentacles to catch food at night. During the day, they use their tentacles for protection by wrapping them over the grooves on their surface. The surface is hard and offers good protection against fish or hurricanes.Image credit: National Oceanic and Atmospheric Administration
