Region: Philippines

Appearance
When the long thin polyps or tiny coral animals are out, the coral almost looks prickly. When the polyps are in, it looks smooth and leathery. A single leather coral colony can be up to 3 feet (1m) across. Colonies of these corals will live so close together, it may look as though one colony extends for hundreds of feet. Individual colonies look like large mushrooms.

Habitat
Leather corals live on sheltered areas of the reef such as dropoffs and along walls where waves and currents carry their food right to their polyps.

Range
Leather corals live in the warm parts of the Pacific Ocean and the Red Sea.

Diet
Extending their long thin polyps, leather corals grab zooplankton or tiny animals and phytoplankton or tiny plants from the water as it drifts by. Most of their nutrition come from the zooxanthellae or algae that live just under the clear skin of the animal. Leather corals have a symbiotic relationship or partnership needed for survival with this zooxanthellae. The algae make food for the leather coral using the energy from the sun. The algae feed off the animal's waste. The coral gives the tiny algae oxygen and a safe place to live.

Most corals that have zooxanthellae contribute to building the hard part of the reef. They are also usually hard corals, which are generally considered the reef builders. This isn't true for leather corals. Leather coral is considered a soft coral because it doesn't produce a skeleton like the hard corals. The stem or stalk that the large coral rests on is made of sclerites or microscopic calcareous particles—almost the same things sponges are made of. After the coral dies, the sclerites really don't leave behind anything for other animals to grow on.

Reproduction
Just like hard corals, the leather corals have mass spawning events. Some factor, like a full moon during the months in the spring or summer when the ocean waters are warming will signal that it is time for all the leather corals to release their eggs and sperm. The millions of brightly colored eggs and smoky-looking clouds of sperm that are released, unite and grow into tiny larvae. The larvae are left on their own to swim off and establish new colonies, often many miles from the parent reef.

Besides forming new colonies through sexual reproduction, corals can form new colonies in other ways. Sometimes rough weather breaks off a piece from an existing colony. If that fragment resettles, it may continue to grow as a new colony. This process is called fragmentation. They can form new colonies through asexual reproduction, or to make an exact copy without eggs and sperm. By budding, coral polyps divide to create new individuals. As more polyps bud, a colony grows.

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Threats and Management
Since leather corals have zooxanthellae, they need lots of sunlight. In the home aquarium, special lighting is needed to mimic the natural lighting conditions, and can be expensive. Corals are also very finicky. They need some conditions to be almost perfect or they will die. Many home hobbyists don't have luck keeping corals, and if they kill the corals, it can be a very expensive mistake. These reasons may have kept the population of leather corals stable.

Did You Know?
Soft corals, sometimes called octocorals, have eight tentacles on each polyp, but hard corals, sometimes called hexacorals, only have six tentacles on each polyp.

Some sea slugs eat leather corals even though they are toxic. The slugs eat the coral and transport the zooxanthellae into certain parts of their body by enclosing their food in special pouches that protects the sea slug from the toxins. Carefully keeping the algae alive, the sea slug gets nutrients from the zooxanthellae, just like the coral does. Not only does the slug avoid getting poisoned by the zooxanthellae, but it also get free meals from them.

Soft corals emit a chemical to keep other animals from growing near them.

References
Print Publications:
Allen, G. R. 1997. Tropical Marine Life. North Claredon, Vermont: Periplus Editions Ltd. 64p. ISBN# 962-593-157-0.

Allen, G. R. & Stene, R. 1996. Indo-Pacific Coral Reef Field Guide. El Cajon, California: Odyssey Publishing Company. 378p. ISBN# 981-00-5687-7.

Colin, P. L. & Arneson, C. 1995. Tropical Pacific Invertebrates. Beverly Hills, California: Coral Reef Press. 296p. ISBN# 0-9645625-0-2.

Debelius, H. 1999. Indian Ocean Reef Guide. Frankfurt, Germany: IKAN. 321p.
ISBN# 3-9317-0267-7.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

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Vocabulary Words

Asexual Reproduction - Reproduction that does not involve the union of egg and sperm; results in an exact copy of the original animal.


Budding - When a coral polyps divides to create a new individual. As more polyps bud, a colony grows.


Extinction - An organism that has not been present on the face of the earth for over 50 years.


Fragmentation - The process through which a new coral colony forms when a piece breaks off an existing colony, resettles on a new area of the reef, and starts to form a new colony.


Organism - A living thing.


Polyp - An animal that does not move because it is attached to a hard substrate; resembles a flower with the bottom of its stalk attached to a stable surface and tentacles and oral arms facing upward; reproduces asexually.


Sclerites - Microscopic calcareous particles.


Species - A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.

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