Corals are marine animals related to jellyfish and anemones. Both colonial and solitary corals catch plankton and other suspended food particles with arm-like tentacles, which feed a centrally located mouth. Most hard corals also host symbiotic algae, a long-standing and successful partnership. These algae provide them with an additional food source through photosynthesis. Coral reefs are formed by corals that secrete hard calcareous exoskeletons, giving them structural rigidity. These colonial “hard corals” form elaborate finger-shaped, branching, or moundshaped structures and can create masses of limestone that stretch for tens or even hundreds of miles.
