Animal or Vegetable? - WA's Corals

If you have ever dived on a coral reef you have surely been struck by the colours, varieties and even the size of the ‘garden’ you have seen. Although they most certainly look like plants, corals are animals attached to the ocean floor. They have 'taken root' as plants do, however, unlike plants, they do not make their own food. Some corals will trap nutrients that drift past while others will feed off small fish that get trapped in their tangle of stems. Most corals feed at night. To capture their food, corals use stinging cells called nematocysts. These cells are located in the coral polyp’s tentacles and outer tissues. If you’ve ever been 'stung' by a jellyfish, you’ve encountered nematocysts. Nematocysts are capable of delivering powerful, often lethal, toxins, and are essential in capturing prey. A coral's prey ranges in size from nearly microscopic animals called zooplankton to small fish. 

Almost all corals are colonial organisms. This means they are composed of hundreds to hundreds of thousands of individual animals, called polyps. Each polyp has a stomach that opens at only one end. This opening, called the mouth, is surrounded by a circle of tentacles. The polyp uses these tentacles for defence, to capture small animals for food, and to clear away debris. Food enters the stomach through the mouth. After the food is consumed, waste products are expelled through the same opening.