Coral
Wiki, Facts

 Coral facts

• They typically live in compact colonies of many identical individual polyps
• The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton
• A coral "group" is a colony of myriad genetically identical polyps
• Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length
• A set of tentacles surround a central mouth opening
• An exoskeleton is excreted near the base
• Over many generations, the colony thus creates a large skeleton that is characteristic of the species
• Individual heads grow by asexual reproduction of polyps
• Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon
• Although some corals can catch small fish and plankton, using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates in the genus Symbiodinium that live within their tissues