A NOTE ON CORALS B.SC. PART 1

By – Dr Archana Kumari Assistant Professor Dept. Of Zoology, Gaya College, Gaya INTRODUCTION

 Corals are marine invertebrates which belong to the class Anthozoa of phyllum Cnidaria  Corals are solitary or colonial polypoid coelentrates (polyp is a sessile and asexual zooid), that lives in a secreted skeleton of their own, some of which have grown into large solid structures and some of which have formed large branched colonies  Few of them also belong to the class Hydrozoa. The hydrozoan corals are Millepora and stylaster  The anthozoan corals are Tubipora and Alcyonium CLASSIFICATION

 Kingdom - Animalia  Phylum - Coelenterata or Cnidaria (corals, jellyfish, sea anemones, hydroids)  Class - Anthozoa meaning "flower-like animals" (corals and sea anemones). Anthozoans give rise to stony corals or true corals and these are the builders of Coral Reefs. The coral colonies grow constantly in size by budding of the polyps resulting in massive coral structures called coral reefs. Corals are restricted to certain regions as they require warm and shallow water to grow like the Caribbean seas, Indo-pacific region, east coast of Africa and the north eastern coast of Australia The body of a coral polyp can be hard or soft depending upon the substance which forms it  Soft corals do not have a hard skeleton. Eg . Tubipora, alcyonium  The polyp of hard corals makes a hard, protective shell out of calcium carbonate. When the polyp dies, the chalky skeleton remains, and another polyp will grow on top of the old one. Eg. Brain coral, elkhorn coral Hydrozoan coral -Tubipora Soft coral - Millepora Hard coral – Brain coral CORAL POLYP

 The soft body of a coral polyp is about the size of a pencil eraser. It has radial symmetry; some corals have 8 tentacles, others have multiples of 6.  Many corals have symbiotic algae that live inside them. (Symbionts are two organisms that help one another.) These algae (called Zooxanthellae) help form the coral's stony exoskeleton.  Corals are carnivores that eat zooplankton (like copepods and tiny marine larvae). They catch food using tentacles that surround the mouth; the tentacles have poisonous stingers (called nematocysts). BARRIER REEFS

 Barrier Reefs are found parallel to the coastline but are separated by deeper and wider lagoons.  They can reach the water surface at its shallowest point and form a barrier for navigation GREAT BARRIER REEF

 The largest and the most famous barrier reef in the world is The Great Barrier Reef of Australia.

Aerial view of great barrier reef ATOLLS

 These are rings of corals or circular horse shoe shaped reefs, situated quite far from the shore, usually located in the middle of the sea  Atoll is also referred to as Coral Islaand or Lagoon Island PATCH REEFS

 Patch reefs are small isolated reefs that grow up from the open bottom of the island platform or continental shelf  They usually occur between fringing reef and barrier reefs  They rarely reach the surface of water BENEFITS OF CORALS

 Corals have built a thick substratum of the earth’s crust  Provide an abode for a variety of aquatic flora and fauna  Some corals are used as ornaments  Red corals and organ pipe corals are used as medicines in South India  Coral skeletons serve as raw material for preparing lime, mortar and cement  Corals reefs also serve as good nursery grounds for commercially important fishes

Coral skeleton made of calcium carbonate