Shedding Light on Bioluminescence

Looking back on your childhood, can you recall catching fireflies on a warm summer night? Or perhaps you saw the movie Finding Nemo and you remember the frightening anglerfish that swam in the dark ocean waters. Different though they seem, the anglerfish and the lightning bug do have something in common: they are both bioluminescent.

Cryptopsaras couesii
Image from Wikimedia Commons

Bioluminescence is defined as a chemical reaction inside of an organism that produces light. Fluorescence, which it is often confused with, lacks this chemical reaction. For the reaction to happen, an organism must contain luciferin and either luciferase or a photoprotein. When the oxidized substrate luciferin and the catalyst luciferase interact in an organism, oxyluciferin and light are created. The result is the same when luciferin and a photoprotein are used. However, this type of reaction requires an extra agent, which is many times a calcium ion. The light produced in both of these comes from the luciferin. Depending on the organism, luciferin can be synthesized or absorbed from another creature. Maintaining a symbiotic relationship with another organism or simply consuming the organism can allow for the luciferin absorption.

Although the chemical reactions in all bioluminescent organisms are similar, organism type and habitat has an important effect on the light being emitted. For example, bioluminescent creatures in the ocean tend to emit a light that humans perceive as blue-green. Plenty land animals also emit this hue, but many others glow yellow instead. As incredible as their light is to look at, the majority of creatures don’t glow continuously, but flash briefly instead.

The functions of bioluminescence can be separated into three categories: offensive, defensive, and communication. As a defensive mechanism, bioluminescence allows creatures to startle other organisms away. It also is used in counterillumination, where the prey manipulates their light’s angles to hide themselves. Some organisms have even been known to use bioluminescence as a sort of burglar alarm, so that larger predators come over and attack the original predator. In other species, a flashing light shows to the predator that they have distasteful chemicals in their body. Another use, called the sacrificial tag, prevents predators from consuming the rest of a bioluminescent organism once they realize the part they ate glows through their stomach, making them a target for other predators. Additionally, bioluminescent prey can misdirect a predator by releasing a luminous body part or by issuing a light smokescreen with glowing particles.

As an offensive tool, many organisms use light to bait prey. Others use their bioluminescence as a flashlight to look for food. Counterillumination can also work as an offensive technique, hiding a predator from its unsuspecting prey. Lastly, many organisms use light to communicate. Like the firefly, many creatures flash their lights to advertise themselves to potential mates.

Overall, bioluminescence serves multiple functions in various organisms. And not only does it benefit animals, but its characteristics could be helpful to humans as well. Bioluminescent light is “cold light”, so it does not release a significant amount of heat. Knowing this, light bulb efficiency could be increased if less energy was wasted as heat. The defense mechanisms associated with bioluminescent organisms are being studied by the U.S. Navy for their submarines. The possible scientific advances that could arise from studying bioluminescence are limitless.


About Mr. Mohn

Biology Teacher

This entry was written by Blair M. and tagged . Bookmark the permalink.

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