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| Sunday, 5 December 2004 |
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Junior Observer |  |
| News Business Features Editorial
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Living beings who build reefs Corals are extremely beautiful and are responsible for the formation of the Great Barrier Reef in Australia.We have our own coral gardens at Hikkaduwa, which attract thousands of tourists both local and foreign. A coral structure is composed of thousands of these tiny animals growing together as a colony. These tiny coral polyps are the builders of the reef. Their tiny calcium shells have accumulated over thousands of years to form the largest living structures in the world.
The majority of corals or 'cnidaria' live as part of a colony, but a few like jellyfish are freely swimming on their own. Most of these animals use special stinging cells called nematocysts to catch their prey. A few of them, particulary the jellyfish, are capable of inflicting extremely painful stings on humans. Although corals come in a wide range of shapes and sizes, they share the same basic body plan. The differences occur due to factors such as genetics, depth of water, strength of water currents and the location of the coral reef. Coral polyps Coral polyps are small marine invertebrate animals. There are two types of corals, hard and soft. Hard corals have an internal, rock-like, chalky skeleton that remains when they die. Huge colonies of hard corals form coral reefs. Soft corals do not have a hard skeleton. Habitat and distribution Corals are found in seas around the world. Large colonies are found in warm, shallow waters, where colonies of millions of coral polyps form vast coral reefs. Reefs are slow growing; they only grow about one inch each year. Life cycle A coral polyp begins its life as a tiny, free-swimming larva, which is the size of a pin- head. It settles on a hard surface and will never move again. Broken pieces of corals that land on a suitable surface may begin growing and produce a new colony. Anatomy
Coral colonies grow in many shapes and in many colours. Many corals have symbiotic (two organisms that help one another) algae that live inside them. These algae help form the coral's stony exoskeleton. Diet Corals are carnivores. They catch food using tentacles that surround the mouth; the tentacles have poisonous stingers. Most corals feed at night. Keeping the tentacles retarded during the day also helps corals protect themselves from Ultra Violet light. Predators Corals are eaten by a large starfish called crown-of-thorns, parrotfish and other animals. Threats to coral reefs Coral and coral reefs are extremely sensitive. Slight changes in the reef environment may have detrimental effects on the health of entire coral colonies. These changes may be due to a variety of factors, but they generally fall within two categories: natural disturbances and anthropogenic disturbances. Although natural disturbances may cause severe changes in coral communities, anthropogenic disturbances are linked to the vast majority of diseases in corals and cover general colony health when coral reefs and humans exist together. One of the greatest threats to coral reefs is human settlement expansion and development. As development continues to alter the landscape, the amount of freshwater runoff increases. As the population increases, so does the harvest of resources from the sea. Due to over-fishing, reef fish populations have greatly decreased in some areas of the world. The removal of large numbers of reef fish has caused the coral reef ecosystems to become unbalanced, allowing more competitive organisms, which were once controlled by large fish populations, to become dominant on reefs in many regions. Corals are also very popular as decorations. Often, when people vacation in tropical locations surrounded by beautiful reefs, they want to take home corals as souvenirs. In most cases, healthy corals are damaged for this purpose. Coral reefs also receive much damage from vessels. The leakage of fuel into the water and oil spills made by large tankers are damaging to local corals. Boat anchors also damage corals by breaking and destroying entire colonies. Animals associated with coral reefs Coral reefs provide habitats for a variety of organisms. These organisms rely on corals as a source of food and shelter. Some use corals for the purpose of protection from predators. Fish also depend on corals for protection. There are many other species of fungi, sponges, sea worms and molluscs that bore into coral skeletons. Other organisms that inhabit the coral reefs include jellyfish, oysters, clams, turtle and sea anemones. ***** Coral snakes Coral snake is the common name used for certain small, brightly coloured, venomous snakes of the family that also includes the cobra. About 50 species of coral snakes are known.They are marked with bright coloured rings or bands that are black, yellow, and red, although the colour and pattern may vary in some species. When threatened, coral snakes usually curl their tails into tight spirals and hold them upright; this behaviour is thought to attract predators to the tail rather than to the more vulnerable head. Most coral snakes feed on small snakes and lizards. Like other members of the family to which they belong, coral snakes have a pair of short fangs fixed in the front of the mouth with which they inject a lethal poison that acts primarily on the nervous system. |
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| Politics | Produced by Lake House |
Although many people mistakenly refer to corals as plants, they are
actually animals. These animals are characterised by a symmetrical body,
usually with stinging tentacles and a central mouth.
The soft body of a coral polyp is about the size of a pencil eraser. It
has radial symmetry; some corals have eight tentacles, others have
multiples of six. The polyp of hard corals makes a hard, protective shell
out of calcium carbonate. When a polyp dies, the chalky skeleton remains
and another polyp will grow on top of the old one.
