t to there advantage, by producing red light that they can use to communicate in "there own language" and navigate to their prey. Without the prey ever being able to see them coming. Yellow and White light is slightly more rare and can be used on the underside of a fish's body to replace the light that it blocks out when swimming over a predator nearer to the surface. This process is called counterillumination. That way the predator cannot single it out. Examples of these is a species are Euphausia pacifica(krill), Histioteuthisheteropsis(octopus), or the hatchetfish.Some organisms constantly produce light. And when they want it turned off they have to cover it with an eyelid-like flap(flashlight fish). Others can turn it on and off when they wish. Like when they need to camouflaging themselves or require light to navigate etc. The angler fish is an example of a species that uses a lure like photophore that extends out under there mouth then when the smaller fish go to eat the bait the angler fish eats them instead. And some other kinds of fish can detach a photophore and escape into the darkness while the predator still goes after the lone photophore. So in conclusion organisms that range from microscopic single celled organisms (dinoflagellates) to one of the longest animals in the world (Praya dubia 50+ meters ) can use bioluminescence for many reasons that are all necessary for deep sea survival. Research in bioluminescence is also a promising field in science. And recently there have been many genetically altered animals like monkeys and rabbits that are bioluminescent. Scientists are also developing ways to use it to locate diseases like cancer and tuberculosis by making the diseased tissue glow....
