Turbinaria is a genus of stony corals belonging to the family Dendrophyllidae. They are also called disc corals, vase corals or pagoda corals. They are one of the three genus in this family that are zooxanthellate, meaning that they live in symbiosis with tiny photosynthetic organisms.
These stony large polyp corals get their name from the common disc shape form the colonies take. Most species have colonies less than 50 centimeters in diameter, although some can grow larger. Members of the genus Turbinaria form foliaceous colonies for the most part, with other shapes such as laminar, columnar even massive in rare cases. The colonies often form plates and discs, with the corallites being usually just a few millimeters in diameter. The corallites have porous walls which are usually sunk inside the skeletal tissue or coenosteum. The septa are orderly arranged, with broad collumelas. The majority of disc corals are nocturnal, although there are a few exceptions, such as T. peltata. These corals are hermatypic, meaning that they build reefs.
Turbinaria distribution and habitat
Most disc corals live in the Indo-Pacific region; species can be found from the Great Barrier Reef in Australia to East Africa, Samoa, Japan, South China Sea and the Red Sea. Since most of the species are zooxanthellate, they prefer shallow waters where light is abundant. However, some species are nocturnal, with most of them extending their tentacles at night to supplement their food.
Turbinaria species are quite common, with some notable species including T. bifrons, T. mesenterina, T. peltata, T. reniformis and T. stellulata. T. mesenterina has corallites which are about 2 mm in diameter, with colonies having interlocking plates. This species can often be found in Arabian sandy waters. T. peltata colonies can grow to several meters in diameter, with folliaceous or encrusting forms often overlapping in tiers. The tentacles of the polyps are thick and they can be up to 1 centimeter long. Colors are usually dark with shades of grey or brown. T. stellulata forms colonies which are encrusting and mostly flat, with star-shaped corallites.
These corals have two ways of feeding. They have the autotrophic dinoflagellate called zooxanthellae in their tissues, which are capable of photosynthesis. Most of the nutrients come from these unicellular protists, mainly organic carbon in the form of carbohydrates, nitrogen and others. In return these organisms have elevated support and access to more light. In deeper waters or shady places, these corals are also capable of heterotrophic feeding, meaning that they extend their tentacles they can use to feed on zooplankton organisms.
Just as with most other corals, the disc corals can reproduce sexually and asexually. The colonies are gonochoristic, meaning that a colony is either male or female. These colonies release huge amounts of gametes during spawning events, the most common being a few days to a week after the full moon in November. Turbinaria species can also reproduce asexually through extratentacular budding, where new polyps are formed between the polyps.