coral

Coral (Favia favus), Ras Muhammad National Park, Red Sea, Egypt. This species of stony corals is massive and forms thickly encrusting dome-shaped colonial corals. There is a great diversity of form even among the same species. The corallites project slightly above the surface of the coral and each has its own wall. The septa and costae linked to the corallite wall are well developed and covered by fine teeth. The polyps only extend and feed during the night. Each one has a small number of tapering tentacles which often have a darker coloured tip; these are called stinger tentacles, or sweeper tentacles. They use these to sweep the water to see if any other coral is in its area; if so, then they begin to sting the other coral. This is commonly known as coral war. Each coral is trying to make sure it has enough room around it so it can continue to grow and have more surface area for its offspring.