Though often referred to as a plant or rock because of its appearance, coral is a living animal. Coral comprises tiny polyps that divide asexually to form the colonies off of which marine life tends to feed. Many organisms hide in and live on coral -- another reason marine animals eat the coral along with the organisms. Coral is crunchy, and divers can often hear these animals chewing.
Parrot fish, which live in tropical marine climate, feed off algae found on live coral, which normally requires them to chew off the coral heads. They crush and chew the coral with grinding teeth in their throats to get to the algae-filled polyps inside. Parrot fish are easy to catch at night due to their colorful appearance. They will often create a transparent cocoon to sleep in, which supposedly hides their scent from predators.
Crown of Thorns Sea Star
Crown of thorns sea stars are live in the Indian and Pacific oceans. The animals are have as many as 23 arms, which they use to glide over coral. They travel in groups of tens of thousands and destroy living coral as they eat it down to almost nothing; the coral may take years to recover. With their long, poisonous spines, they are known as one of the most destructive marine animals. Conservationists have tried to control their population through methods including fencing in areas of coral. Due to the sheer width of the ocean floor, however, this process is only a stepping stone.
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Butterfly fish, the most commonly seen fish on reefs through out the world, can exhibit colors such as blue, red, orange or yellow. They eat coral which contains food sources they like such as polyps, worms and other small invertebrates. These fish usually mate for life and stay together with their offspring. They travel in large schools, and if one mate dies, the other usually follows shortly after. These fish often become aggressive as they defend specific coral reefs, which help scientists determine which type of butterfly fish eat which type of coral.
Nudibranchs include more than 3,000 species of sea slugs that feed off coral. These slugs have the ability to emit toxic secretions and defend themselves with stinging cells. They do not make the poison themselves; they take toxins from sponges and other food to create the toxins within their body. Besides coral, these animals eat sponges, barnacles, eggs and other small marine animals -- including one another. They normally have a lifespan of a little more than a year. Scientists say they have only uncovered half of the known species of nudibranch.