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The Beauty of Bioluminescence

  • Writer: Sophia Yang
    Sophia Yang
  • Apr 8
  • 7 min read

Updated: Apr 10

In a routine fashion, the hustle and bustle throughout the day would gradually simmer to a muted hum, enveloping the tired and overworked into a gentle embrace. During these precious hours of tranquility, the night yet again serves as a cue for the masses to unwind and reflect on the blessings and turmoil of their day. Streetlights, lamps, and television sets surround the world in blinding luminescence of vibrant colors, putting on a magnificent performance for all. Yet, along the coastal shores and the sandy beaches, the ocean waters have something more captivating in mind. 


From the shoreline, faint glimmers of bright blue, green, and purple might surface on the periphery of the vast waters, analogous to tiny embers one might observe from a burst of flame. However, upon closer inspection, these sparks possess an all-encompassing nature as they dye the translucent ocean in large streaks. If one heads out to sea, one might notice enthralling sea creatures of multitudinous sizes, from plankton to imposing fish, all emitting light from within their bodies. Although seemingly absurd and fantastical, bioluminescence, also known as nature’s very own light show, might be more common than one may think. 



What is Bioluminescence?

Bioluminescence is defined as the production and subsequent emission of light by a living organism. Bioluminescent organisms are found not just throughout marine habitats, but also on land, though they are rarer in the latter ecosystems. This difference in abundance can be attributed to the complete lack of light in the ocean 1,000 meters below sea level, which creates an increased need for marine organisms to be bioluminescent. The ecological diversity of these organisms should not be undermined, as most types of aquatic animals, from plankton to sharks, include bioluminescent members, creating a tremendous variation and much room for scientific exploration. In fact, scientists estimate that more than 75% of the animals that live in the open ocean are bioluminescent organisms


Origins of Bioluminescence

Some of the earliest recordings of bioluminescence were thought to have come from religious writings of ancient Eastern civilizations, specifically the Greeks and the Romans. In later centuries, French philosopher Jacques Rohault sought to explain why the sea would shine in violent agitation, but not in stagnant water. He believed that in violent waters, waves throw out an infinite number of sparks into the air, and this communicates a force sufficient to produce light. Unlike in violent waters, stagnant water does not produce these same sparks. Rouhault’s hypothesis, although proven wrong, aided in kickstarting investigation into the causes and reasons behind bioluminescence. Later, in  1888, Elihardt Wiedemann coined the term “luminescence”, for all phenomena of light which are not solely conditioned by a rise in temperature.


In 1667, chemist Robert Boyle documented that air, which later was discovered to be oxygen, was a condition required for bioluminescence, thus representing a new era in the characterization of the phenomenon. Later in the nineteenth century, French pharmacologist Raphael Dubois performed an experiment where he extracted the two fundamental components of a bioluminescent reaction and generated light. Dubois coined these two key components luciferin and luciferase, and these findings played an essential role in fully understanding the approach towards manufacturing bioluminescence artificially, as well as the chemistry of bioluminescence.


However, when mentioning figures of importance in the study of bioluminescence, one must not overlook American zoologist E.N Harvey’s contributions to the field. From 1911 to 1951, Harvey wrote an astounding 240 papers and 4 books on bioluminescence, pioneering studies of bioluminescence in new species. Combined, the aforementioned work in this field played a distinct role in the overall understanding of the world, especially in marine habitats. 


Science Behind Bioluminescence

As established in the previous section, to generate bioluminescent light, luciferin and luciferase are required. However, in some cases, luciferase may be substituted with photoprotein. The formation of bioluminescence occurs through an enzymatic reaction, where luciferin is the substrate, and luciferase or photoprotein is the enzyme. 


The arrangement of luciferin molecules determines the bioluminescent color in different organisms. Additionally, some organisms produce luciferin on their own, like dinoflagellates –which is a type of plankton. However, some bioluminescent organisms are unable to self-synthesise luciferin, and instead absorb it from other organisms. The most common example is the housing of bioluminescent bacteria in light organs, where the organism and bacteria then share a symbiotic relationship. 


To create light, luciferase oxidizes luciferin in the presence of oxygen, thereby producing oxyluciferin as a byproduct. Through this reaction, bioluminescent organisms can be bioluminescent. Alternatively, reactions involving luciferin and photoprotein produce light similarly but often require calcium ions as a catalyst. 


Advantages of Bioluminescence

Indeed, bioluminescence is a wonderful sight to behold. But beyond this, bioluminescence is a useful mechanism for animals to possess, prey and predator alike. 


Communication

Bioluminescence allows invertebrates, which are generally considerably smaller, to communicate with organisms that are much larger and potentially far away. A bioluminescent flash can be seen from great distances by other animals. For example, a single-celled dinoflagellate, which is 0.5mm long, can send a signal to a fish 5m away – a distance 10,000 times its size! The only other method of communication, chemical cues, do not diffuse rapidly enough to send acute signals across distances that are possible through bioluminescence.

Defense

Bioluminescence is commonly used as a defensive mechanism to ward off or distract predators. When a bright, bioluminescent flash is stimulated at close range, it can startle predators, causing them to hesitate and lose sight of their prey. Some animals can also secrete a bioluminescent smoke screen, which is analogous to a cloud of sparks or glowing fluid, making it challenging for the predator to track the location of its escaping prey. For example, the vampire squid emits a cloud of luminous secretions from its arm tips (Robison et al. 2003), instead of a usual ink sac.


Fig 1. Blue jellyfish hard at work in the dark ocean, illuminating the sea with their bioluminescence
Fig 1. Blue jellyfish hard at work in the dark ocean, illuminating the sea with their bioluminescence

There are also incidences of losing a sacrificial tag, where an organism may lose part of its body during an encounter with a predator. These dead tissues, which can glow for hours, attract the attention of other predators, acting as a decoy. Meanwhile, the organism escapes its predator while regenerating its missing appendage. 

Offense

On offense, bioluminescent organisms may either utilize the techniques of mimicry or illumination.


The use of mimicry involves emitting a glow of light intentionally, either to counter-illuminate shadows or to mimic the shadow of a small predator so that its prey has a disillusioned sense of its actual size and location. These prey are drawn to the light and get within striking distance, falling victim to their predators. For example, the cookie-cutter shark uses the technique of counter-illumination to mimic a school of small fish (Raad and Jathoul 2024), fooling fish below them into thinking that prey is within distance. As these fish swim towards the shaft of light, the cookie-cutter shark attacks.


Bioluminescent predators who inhabit deeper areas of the sea have evolved to emit red light, instead of the usual blue. This light frequency allows them to better identify potential prey, as most fish in the deep ocean are unable to see red light. This way, predators can sneak up on their prey.


Scientific Applications of Bioluminescence

Bioluminescence is used for a myriad of purposes in today’s society, and even though much is still unknown about this phenomenon, its function in the scientific world is essential. Below are a few primary uses of bioluminescence.


Bioluminescence Imaging

Bioluminescence is appealing as an approach for in vivo optical imaging in mammalian tissues at the molecular level, due to the exceptional sensitivity and specificity afforded by this technology (Syed and Anderson 25). Other forms of light imaging, like fluorescent imaging, use fluorescent radioactive tracers – which possess a shorter shelf life. Thus, this requires a constant replenishment of resources, making this method costly. Alternatively, bioluminescent probes used in bioluminescent imaging (BLI) do not have this disadvantage.


BLI has been extensively used in many biomedical contexts, spanning from the imaging of developing tumours to  infectious diseases. This system is able to monitor the growth and development of genetically modified pathogens. Moreover, BLI is low-cost, and non-invasive, enabling the study of ongoing biological processes, serving an important purpose in scientific research.


Hygiene Monitoring

For several decades, bioluminescence-based sensing technology has been of great use in hygiene control, being routinely used to monitor the cleanliness of surfaces in hospitals, clinics, and dairy and meat processing industries (Syed and Anderson 16). The speed and ease of analysis when using bioluminescent light has led to extensive usage of this technique in a variety of settings. 


Additionally, bioluminescence measurements and technology are frequently used to monitor quality control and hygiene in the food industry. For example, bioluminescent lighting has been used in fish processing plants for decades to determine contamination levels. This system is able to detect both live and dead cells, differentiating between different types of microorganisms, even in varying processing environments. 


What is most interesting about bioluminescent technology is how effectively it can monitor the growth of live bacteria on organisms, in turn accurately assessing its quality. Lux genes responsible for bioluminescence can be genetically encoded into bacteria that are not naturally bioluminescent. Through this mechanism, key indicators like the localisation, population size, and environment of these bacteria can be monitored in real time. 


Conclusion

Indeed, the uses and advantages that bioluminescence entails in today’s world are extensive. As science and technology continue to develop, bioluminescence do more than appease the eye, but also act as an indispensable mechanism for animals and humans alike to thrive. 


 

Written by Abigail Tan


References


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