When you think of bioluminescent organisms, jellyfish probably come immediately to mind. This is probably the most well-known example of a bioluminescent organism, but a team of scientists from the American Museum of Natural History have just published research that shows a huge number of fish species exhibit bioluminescence as well we just never noticed until now.
Bioluminescence is the capacity of an organism to absorb and redirect light at a lower energy level. Since water is very good at absorbing light, the higher energy blue end of the spectrum penetrates more deeply into the sea. This blue light is absorbed and re-emitted as green or red by the fluorescent proteins in organisms.
The light display produced by fish is much more subtle than the jellyfish. In fact, if youre not looking through the right filter, the reflected blue light will drown out the bioluminescence. Thats probably why the scale of fish bioluminescence wasnt known until now.
To figure out which fish glow and which dont, the researchers led by John Sparks and David Gruber took to the seas with a high energy blue light. The divers and the cameras were outfitted with yellow visor filters that blocked the reflected blue light, thus allowing the bioluminescence to be seen. Bioluminescent fish have the same kind of lens in their eyes that allow them to see other glowing creatures.
In all, the team identified over 180 species of bioluminescent fish across 16 phylogenetic orders. It is believed that the colors and patterns of light are used in mating, communication among a species, and possibly even camouflage against some backgrounds.
This isnt just a neat factoid to put in the text books, though. The discovery and sequencing of jellyfish Green Fluorescent Protein (GFP) was a revolution for biochemistry and genetics. Associating this easily visualized gene sequence with genes in other species allows scientists to study how genes and proteins are copied and moved around. The fluorescent proteins in fish might prove to be very powerful tools in the future.