Marine Animal Encyclopedia
Many marine organisms, particularly those in the deep sea, make use of bioluminescence, the biochemical emission of light. Many of these creatures depend on bacteria, such as the rod-shaped Vibrio fischeri, to generate the light, and in these cases the bacteria live within the body of their host in a mutually beneficial relationship. The bacteria produce light using a chemical reaction that takes place inside their cells. Vibrio fischeri also occurs as a free-living organism, moving through water by means of a flagellum and feeding on dead organic matter. The distinctive, comma-shaped cells seen in Vibrio fischeri are characteristic of the genus. Other Vibrio species (which are not luminescent) are responsible for the potentially fatal disease cholera.
Eyelightfish have light-emitting organs called photophores under each eye. The light is produced by colonies of Vibrio fischeri living in the photophores. The light organs display distinct patterns, and may be used as an aid to recognition and communication between fish of this species. The ability to emit light may also play a part in prey capture and the avoidance of predators.