by Julia Cohen, Michelle Gervais, Alexandra Moisan.
Bioluminescence is an emission of light caused by an oxidation reaction that occurs in living organisms. Many diverse microbes and marine animals are able to produce their own light, predominantly those concentrated in the ocean. This light production can be used as a means of communication among a species. The compounds involved in the chemical reaction are luciferin and either luciferase or photoprotein (1). Luciferin produces the light and the luciferase or photoprotein acts as the catalyzing protein of the oxidation reaction (6). The light given off is referred to as cold light as it is 100% light energy. This means that none of it’s energy is transformed into heat (5).
Many deep sea fish will use bioluminescence as a lure in order to attract prey. Anglerfish, for example, grow a long appendage that hangs in front of them is used to bait smaller fish into swimming within striking distance. Other fish also use bioluminescence to attract their prey; the cookie cutter shark’s entire body is lit up except for a small patch on it’s stomach that resembles the shadow of a smaller fish. This small shadow-like patch lures in larger predatory fish, who upon attempting to attack what they believe to be a smaller fish, are met with the cookiecutter shark that preys on them (2).
Many marine animals use bioluminescence to attract mates. Ostracods, or crustaceans that can be found in the western Caribbean sea, use a complex combination of lights to attract their mates. There are over a dozen different species of Ostracods living within similar habitats. In all of these crustacean species only the males produce bioluminescent light and yet their mating displays are all very different (4).
A non aquatic example of bioluminescent attraction occurs in fireflies. These insects use their bioluminescence to attract a mate and, similarly to the crustaceans each species has its own distinct lighting pattern. The differing patterns allow the female to be drawn to a male of their own species (5).
Bioluminescence is used by some animals to scare off predators or to distract them long enough to escape. Swima Bombiviridis, also known as the green bomb worm, releases a flash of bright green bioluminescent light when threatened. The same tactic is used by certain squid that produce bioluminescent liquid instead of ink. They release this liquid to distract predators while they escape (2).
It is estimated that bioluminescence has evolved at least 40 times independently, but most likely 50 times among extant organisms. Non Symbiotic luminous organisms possess the gene for either luciferase or photoprotein, which are the compounds required to produce bioluminescence. It is believed that for bacterial symbionts, the trait may have evolved only once, but each marine animal lineage that uses those microbes has had to develop specialized organs to host the light and maintain the bacterial culture (10). A type of luciferin known as coelenterazine occurs in many marine bioluminescent groups. It previously had antioxidant properties that helped defend aquatic species from oxidative stress. Oxidative stress is a chemical imbalance that occurs in a body and is cause by free radicals. At some point there was a shift from its antioxidative function to the light emitting function that exists today. This is most likely due to the fact that the need for antioxidative defence mechanisms decreased when marine animals began inhabiting deeper waters. In these waters, the animals were less exposed to oxidative stress because there is less light and oxygen available. Within the organisms, there was a reduction in metabolic activity as they increased their depth in the sea. As a result, through evolution, these organisms developed mechanisms to create the bioluminescence produced by coelenterazine that can be seen today (9).
Dinoflagellates of Costa Rica
In Costa Rica we observed bioluminescent dinoflagellates, which are a type of plankton. Ninety percent of all dinoflagellates are marine plankton. Dinoflagellates are approximately 0.04 mm in size, making them invisible to the naked eye, and are present in large agglomerations in the epipelagic zone of the ocean which is located up at the surface (7). Dinoflagellates are motile, they move by means of two flagella, a protein and microtubule strands which propel it through the water. They have an internal skeleton made of cellulose like plates (8).
Dinoflagellate Bioluminescence Chemistry
These tiny marine organism produce light through a luciferin-luciferase reaction. The luciferase found in dinoflagellates is related to the green chemical chlorophyll found in plants (1). Although the chemistry of the dinoflagellates luminescence is not completely understood, it is most likely caused by a drop in pH due to an influx of protons within its cell. It is an extremely fast cellular process and the dinoflagellate can produce a flash of light lasting up to 100 ms. However, once all its luciferin has been oxidized, it must wait until the following day for its chemicals to recharge to be able to flash again. (8) The cell alternates between photosynthesis and luminescence on a 24 hour cycle.
Ecological Roles and Relationships
Dinoflagellates use their luminescence for many different ecological functions. These protists can be autotrophic or heterotrophic. Photosynthetic dinoflagellates are important primary producers in coastal waters; some are symbiotic living in their hosting coral cells. Seen as they are small photosynthetic organisms, they are at the bottom of the food chain. Because of this, many aquatic creatures prey on them. Therefore, they primarily use their bioluminescence as a defence mechanism. By emitting light when stimulated by movement they can scare away smaller predators. They also act as a signal to larger predators. When they light up they draw the larger predators in, signaling the presence of a smaller predator they can prey on. This indirectly protects the dinoflagellates, creating a mutualistic relationship with the larger coastal predators (7).
- “Bioluminescence.” National Geographic Education. National Geographic, 13 June 2013. Web. 25 Mar. 2016. <http://education.nationalgeographic.org/encyclopedia/bioluminescence/>.
- ”Adaptations for Bioluminescence – Bioluminescence.” Adaptations for Bioluminescence. Smithsonian National Museum of Natural History, n.d. Web. 25 Mar. 2016. <http://www.biology-online.org/articles/bioluminescence/adaptations-bioluminescence.html>.
- ”Dinoflagellate Bioluminescence.” Latz Laboratory. Scripps Institute of Oceanography, 09 June 2014. Web. 25 Mar. 2016. <https://scripps.ucsd.edu/labs/mlatz/bioluminescence/dinoflagellates-and-red-tides/dinoflagellate-bioluminescence/>.
- Rivers, Trevor J., and James G. Morin. “Complex Sexual Courtship Displays by Luminescent Male Marine Ostracods | Journal of Experimental Biology.” Complex Sexual Courtship Displays by Luminescent Male Marine Ostracods | Journal of Experimental Biology. Journal of Experimental Biology, n.d. Web. 27 Mar. 2016. <http://jeb.biologists.org/content/211/14/2252.long>.
- United States. National Park Service. “Synchronous Fireflies.” National Parks Service. U.S. Department of the Interior, n.d. Web. 27 Mar. 2016. <https://www.nps.gov/grsm/learn/nature/fireflies.htm>.
- Nealson, K. H., and John W. Hastings. “Bacterial bioluminescence: its control and ecological significance.” Microbiological reviews 43.4 (1979): 496.
- Wilson, Thérèse. Bioluminescence. Harvard University Press, 2013.
- ”Dinoflagellate Bioluminescence.” Latz Laboratory. Scripps Institution of Oceanography. UC San Diego, 09 June 2014. Web. 05 Apr. 2016.
- Others, J.-F. Rees. “THE ORIGINS OF MARINE BIOLUMINESCENCE: TURNING OXYGEN DEFENCE MECHANISMS INTO DEEP-SEA COMMUNICATION TOOLS.” The Journal of Experimental Biology 201, 1211–1221 (1998): 1211. Web. 5 Apr. 2016.
- Haddock, Steven H.D, Mark A. Moline, and James F. Case. “Bioluminescence in the Sea.” Marine Science 2 (2009): 443-49. Web. 5 Apr. 2016.