Biofluorescence: Light Fish See and Reflect


Under the ocean, in the murky bottom weighted with tons of water, fish swim in what many consider the deep, dark sea, but it is now been revealed that by creating biofluorescence fish see and reflect light.  Unperceived by the human eye, whether looking at photographs or enhanced with technological breathing support while exploring the underwater universe, there is natural light.

The light the fish see and subsequently reflect via biofluorescence, sometimes in spectacular colors, like day-glow green, sanguine red and vibrant orange, is not generated by the fish, but by the perception of light around the fish. The fish then absorb and reflect back in a chemical reaction involving luciferin and luciferase, an enzyme. Both words are based on the Latin root “luficer” or “bearer of light,” which explains well the process of bioflourenscence.  The difference between luciferin and luciferase is that luciferase is a generic term for a category of oxidative enzymes or organisms and luciferin is a light emitting compound.

Biofluorescence is the reaction between moving organisms and light emitting compounds from an electrical source.  It is a manner of direct communication between the fish and their environment.  The main concerns of fish are reproduction and longevity. It is believed by scientists that the absorption of light and the following reflection of it from the fish back into the sea are signals concerning mating and the nearness of predators.  The fish only emit bright colors when there is light in their vicinity to trigger the chemical reaction.



Why are humans underwater unable to observe sources of light while fish can? Fish can see well in what is termed “blue light.” This term explains why humans see the blue sea, while fish can perceive blue light in the sea.  The speed of natural light is slowed by the weight of water, thus the waves of light become slower; the fish eye is able to track this slower light. The reflection of the blue light from the fish’s body is perceived by fish on other fish and it is not visible by humans.  It’s only through research using special cameras and artificial light as in this recent study brought out by the American Museum of Natural History that scientists and the world at large can look closer at the secret of lives of biofluorescent fish.

The study found more than 180 species fish clearly showing traces of bio-fluorescence, sometimes the bright colors were relevant only to a specific part of the fish rather than completely encompassing the entire fish.  The enlargement of the number of species in the biofluorescent category was a surprise for the research team and rather a scientific coup among those that study oceanography.   Can people emit the same glow?  If humans are placed under a black light, they will emit natural fluorescent compounds.  It may be in the future that more research on the phenomenon can lead to tracking the intake and digestion of medicine for better medical care.  The team plans to investigate more “bony” fish and further research sharks to track more underwater species as to whether they also see and reflect light creating biofluorescence unobserved by the naked human eye.

By Persephone Abbott


Los Angeles Times

The Bioluminescence Webpage

Science Recorder


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