Updated by: Arabinda Naik
The coral polyp develops from a planula which secretes a skeletal rudiment or prototheca with the help of ectodermal and basal plate. Radial folds of the larva secrete septa and a rim is built up around the polyp. Meanwhile, further skeletal material is added into the gaps between the septa. The septa alternate with the mesenteries of a living coelenterate.
Hard corals tend to secrete calcium carbonate underneath their bodies. This turns into a hard, rock-like structure upon which other coral larvae can settle. Over time, as the calcium carbonate builds up and corals reproduce, the size of a coral reef grows. As a coral reef begins to grow, other animals and species are also attracted to the diverse habitat and find places to settle and call home. Over 25% of all marine life can be found on coral reefs. Each plays a unique role in helping to keep the ecosystem healthy and intact.