LOUISE MURRAY / SCIENCE PHOTO LIBRARY LOUISE MURRAY / SCIENCE PHOTO LIBRARY
Galaxea hard coral polyps extended during the day. This hard coral consists of colonies of individual animals called polyps, which build the coral around them to form a protective skeleton. The coral consists of hard spikes surrounded by the soft tentacles of the polyps. The tentacles have nematocysts (stinging cells) that are used to catch small prey as they swim past. Once stung, the prey is moved to the opening of the polyp's gullet by the tentacles. The polyp may also feed by filtering zooplankton from the water. Photographed in Lembeh Strait, off Sulawesi, Indonesia.
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