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Bioluminescence: The Living Light

Updated: Jul 18, 2020

Bioluminescence is the ability for a living organism to produce light. "Bio" means life, and "luminescence" means light.

Bioluminescence is pretty rare on land, though there are some land organisms that emit light like fireflies, glow worms, and some mushrooms. In the ocean, bioluminescence is more common. In the deep sea where there is no light, 90% of the animals are bioluminescent.

Organisms create bioluminescence through a chemical reaction in their bodies. This creates a "cool light" meaning it does not give off heat the way a light bulb would.

Organisms that give off bioluminescence usually do it as a defense against predators, to hunt for prey, or to find mates.

Watch this video on bioluminescence:

Examples of land bioluminescence:


One of the reasons fireflies use bioluminescence is to find a mate. Each species of firefly has a unique flash pattern and fireflies can locate a mate of their own species through this pattern. Females may also choose a mate based on the speed and intensity of their flashes.

Glow worms:

The glow worms in this video are the larval stage of a fungus gnat. They drop sticky threads that dangle from the roof of the cave. The light they emit attracts bugs (in the same way that moths that fly toward a porch light) which get stuck in the web, and feed the glow worm.

Examples of marine bioluminescence:

  • Find or attract prey: Anglerfish use a light that dangles above their foreheads to attract prey. Their prey are drawn to the light, and once they get close to the anglerfish's mouth, they're a snack!

Flashlight fish have bioluminescent bacteria that live in a flap below their eyes. They hunt for food at night, so the light helps the flashlight fish find their meal.

  • Defense against predators: Some squid and shrimp shoot out a glowing bioluminescent cloud when scared, to distract their predators. Some brittlestars and jellyfish will release a leg or tentacle that glows and continues moving to attract the predators attention while they get away (brittlestars can then regrow their leg and some jellyfish can regenerate as well).

  • Communication: When bristle worms mate, the females create a glowing cloud of gametes that attract males to come fertilize.

Red Tides:

Ride tides are caused by a big increase in the number of dinoflagellates in an area of the ocean. Dinoflagellates are a tiny floating algae, or marine plankton. Warming water or an increase in nutrients may feed the dinoflagellates, causing them to multiply. These dinoflagellates give off bioluminescence when they are disturbed by any movement, and when there is an algal bloom, or red tide, the results are beautiful to watch.

As the water moves, each dinoflagellate puts off a warning signal in the form of a flash of light. When there are billions of them, they light up the water in a really beautiful way. The dinoflagellate glows as a defense. Dinoflagellates illuminate their predators when they are touched, making the predators visible to their predators. Hopefully the dinoflagellates predators will be eaten before they eat the dinoflagellate.

Though the bioluminescent glow of red tides are beautiful, the algal bloom is sometimes toxic, meaning it will kill the marine life in the water. Even when it is not a harmful algal bloom, once the red tide has run its course (usually after a couple of weeks), the algae dies off, and the oxygen in the water declines due to the decomposition of the dinoflagellates. When the oxygen drops, fish and other marine life will die off. This is the reason we need to keep our oceans clean and free of pollution, and try our best to slow climate change.

Activity #1:

On a piece of paper, answer the following questions:

  1. What is bioluminescence?

  2. What causes bioluminescence?

  3. What are the three main reasons organisms use bioluminescence?

  4. If you had bioluminescent ability, what would it be and how would you use it?

  5. Given that climate change has continued to make many areas of the world warmer and warmer, do you think there will be more red tides than in the past? Why?

Activity #2:

Choose one of the following fish to read about:



Northern Lampfish

  • Draw a picture of your fish

  • Describe where it lives, what it eats, and what it uses it's bioluminescence for.

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