Bioluminescence: Definition & Types

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Bioluminescence is an amazing phenomenon where a chemical reaction within a living organism causes it to produce and emit light. Read this lesson to learn how this happens and where you can go to see it for yourself!

What Is Bioluminescence?

This is one of the coolest topics in biology! Bioluminescence is when a living organism produces and emits light. You're most likely familiar with bioluminescence caused by fireflies, but bioluminescence is much more common in the ocean than on land (and it's almost completely absent from freshwater bodies).

How does this happen? Well, a chemical reaction takes place inside the organism and light is one of the end products of that reaction. Chemical reactions that produce light are called chemiluminescence, so what you're really witnessing, if you're lucky enough to be in the area, is chemiluminescence happening inside an organism, causing bioluminescence. No matter how you break it down, bioluminescence allows you to see a spectacular natural light show. The most common light color produced is a blue-green hue. Organisms usually only produce one color, and the flashes of light are most often intermittent, lasting less than 10 seconds at a time.

Bioluminescence in corals.
Bioluminescence in corals

Chemical Reactions Causing Bioluminescence

All reactions causing bioluminescence involve a chemical called luciferin. This is the substance that actually produces light. Some organisms make luciferin themselves, while others acquire it though food or by absorbing it from other organisms.

Luciferin then interacts with either luciferase or photoproteins, depending on the type of organism. Luciferase is the most common second chemical that reacts with luciferin, and it's an enzyme that basically jumpstarts the reaction, making it happen. As a result of the reaction occurring, light is produced, and this is what we see in bioluminescence.

The second type of chemical that can react with luciferin is called a photoprotein. These are much less common than luciferase; however, they can still chemically react with luciferin. The catch is that for photoproteins to react with luciferin, calcium ions must also be present. Without these calcium ions involved in the reaction, no light will be produced.

Why Use Bioluminescence?

Sure, it's cool to watch living things emit light, but what is the reason behind that type of mechanism? There are three primary uses of bioluminescence. The first reason is to lure in prey. One of the best-known examples of this is the anglerfish, which lives in the deep ocean where sunlight doesn't reach. The anglerfish partners with bioluminescent bacteria to create bursts of light that attract smaller organisms, providing an easy meal for the anglerfish. Interestingly enough, bioluminescence is the dominant source of light in the deep ocean. Certain species of fish, bacteria, and jellyfish are capable of bioluminescence.

The anglerfish uses bioluminescent bacteria to lure in prey.
Bioluminescence in an anglerfish

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