Shedding some light on Bioluminescence
What are those lights in the ocean? Walking along the beach at night and you see shimmering lights in the vast ocean spread. What is being seen is the emission of visible light by organisms due to a natural chemical reaction known as bioluminescence. In most parts of the ocean, bioluminescence is the primary source of light (Haddock, S. H.D.; Moline, Mark A.; Case, James F., 2012). Two chemicals are required for this reaction to occur; one that produces light, which is called luciferin and the other chemical that drives the reaction, is called luciferase (Haddock, S.H.D.; McDougall, C.M.; Case, J.F., 2012). Having –ase at the end of a word means that it is a catalyst (enzyme) which speeds up a reaction or drives the reaction to completion. Luciferase is used to catalyze the oxidation of luciferin, resulting in light and an inactive oxyluciferin. Luciferin is usually brought into the system through diet or internal synthesis. From bacteria to fish bioluminescence is widely spread throughout the oceans habitats.
Bioluminescence can be found anytime and at any region or depth of the ocean. Dinoflagellates (zooplankton) are often bioluminescent and can be seen lighting up bows or wakes of a ship. Even with tides at night, the waves will cause the dinoflagellates, bacteria, and other organisms to light up creating blue waves. These organisms light up due to movement of other organisms or disturbances in the water (Haddock, S.H.D.; McDougall, C.M.; Case, J.F., 2012). Bioluminescence is primarily a marine wonder and is mostly absent in fresh water. In terrestrial habitats there are glowing funguses on different woods (foxfire) or luminous insects (fireflies).
Different uses of bioluminescence include; finding food, attracting mates, evading predators, and communicating in the sea. Different research has been done focusing on the defense and offense in the use of bioluminescence. In deep, dark water bioluminescence can be used to light the waters to find food available (Widder, E. A., 2010). Along with food, organisms such as fish, use this coloration to attract mates by communicating through the light and different pulses and also to somewhat “show-off”.
A lot of research has been done on how zooplankton is attracted to luminous particles that are rich in organic food (bacteria). One research article (cited below) stated that luminescence is quorum-dependent. This means particles are poor in available organics and are unlikely to sustain a sufficient density of bacteria to generate the luminescence (Zarubin, M.; Belkin, S.; Ionescu, M.; Genin, A., 2011). The article tested two different bacteria having one be able to glow and the other not. There were two separate bags, one filled with bioluminescent bacteria and the other bag with bacteria that were no longer bioluminescent. The research showed that zooplankton was attracted to the glow of the bacteria (in dark waters), rather than the bag with non-glowing bacteria. The research also displayed that with the ingestion of luminous particles, zooplankton started to glow, attracting its own predators. This occurred because bacteria are able to survive digestion in the guts of zooplankton and fish, which they then gain a nutrient rich environment. This allows proliferation and capable dispersal of the bacteria.
Fish predators were then eating zooplankton (due to the light attraction and visibility) and the fish began to glow (Rees, JF.; Wergifosse, B.; Noiset, O.; Dubuisso, M.; Janssens, B.; Thompson, E., 2011). In research done it tracked bioluminescent bacteria through the fish into their fecal matter. So, the bioluminescence stayed lit in the fish throughout the entire period they were living within the fish or zooplankton.
Being able to see light at depth organisms have gone through adaptations making their eyes larger, funneling the energy to their vision (Zarubin, M.; Belkin, S.; Ionescu, M.; Genin, A., 2011). Most deep-sea animals studied seem able to see light only in the blue-green range. These shorter wavelengths (blue and green) penetrate the water farther and are where the majority of bioluminescence falls. But, recent research has been done on bottom dwelling crabs that can distinguish different types of bioluminescent light even into the ultraviolet range (Schrope, M., 2007).
Peter Herring discovered red bioluminescent “searchlights” under eyes of certain species of dragonfish. The searchlights are results of fluorescent proteins, shifting blue bioluminescence into the red range (Herring, P., 2007). These red bioluminescent dragonfish is an adaption that can only been seen by other red bioluminescent organisms or ones that have the pigments to see red at such depths. This gives them somewhat of an advantage, only communicating with each other and not being seen by other organisms, including their predators. Later in the research it was discovered that one dragonfish did not have these special pigments but discovered the use of chlorophyll pigments from bacteria for the red vision (this has been tested in mice and results agree to increasing amounts of red pigments).
Overall, there has been a lot of research done with the symbiotic relationship between zooplankton and bacteria, and how bioluminescence can be used in the defense and offense of organisms at sea.
San Diego Surfers Ride Bioluminescent Waves 2011