Bioluminescence is a cold light produced by living organisms. On land, only a few nocturnal animals, such as fireflies, produce light, but in the ocean, thousands of species produce light. Deep-water fish and squid use bioluminescence extensively, but there are many other producers of light, such as species of bacteria, dinoflagellates, sea pens, jellyfish, mollusks, crustaceans, and echinoderms. Evidence suggests that marine organisims use bioluminescence for defence (as camouflage or distraction), for finding and luring prey, and for recognizing and signaling to potential mates.