Bioluminescence

Marine environments support a number of bioluminescent organisms including species of bacteria, dinoflagellates, jellyfish, coral, shrimp, and fish. On any given night one can see the luminescent sparkle produced by the single-celled dinoflagellates when water is disturbed by a ship's bow or a swimmer's motions. Many multicellular marine organisms have specialized light emitting organs that project light in a particular direction or convey a unique shape to the light. The anglerfish has a light-emitting organ that projects from its head, which serves as a bait to attract smaller prey fish. The light emitted from this organ in the anglerfish is actually produced by bacteria, living in a symbiotic relationship in which both the fish and bacteria profit from their shared existence.

Bioluminescent organisms in the terrestrial environment include species of fungi and insects. The most familiar of these is the firefly, which can often be seen glowing during the warm summer months. In some instances organisms use bioluminescence to communicate, such as in fireflies, which use light to attract members of the opposite sex. Certain reef fish use light produced from organs under their eyes to illuminate the interior of crevices and caves. This not only helps the fish to navigate, but also allows it to locate prey. Organisms that are unpalatable or dangerous, such as jellyfish, use bioluminescence as a signal to warn off attacks by predators. A newly-discovered deep sea octopus has bioluminescent organs in place of suckers.