Anemones and certain species of coral live in isolation, however most corals form colonies made of many single polyps. Polyps are connected and can share “food”.
Stony corals secrete an exoskeleton of calcium carbonate ( CaCO3 ) which makes it hard. The accumulation of skeletal material, broken and piled up by wave action produces a massive calcareous formation that supports and protect the living corals.
Shapes of colonies depend strongly on environmental conditions (light, ocean currents, temperature). The same species may take different form in different part of the world. Corals can resemble of bushes or plates, many have irregular shapes, some stony corals look like “brain”.
The research leading to these results has received funding from the European Community´s Seventh Framework Programme (FP7/2007-2013) under Grant agreement n. 217766 