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Bioluminescence in Fish, Insects & Cats

Instructor: Joanne Abramson

Joanne has taught middle school and high school science for more than ten years and has a master's degree in education.

Bioluminescence is one of the many wonders of our world. In this lesson you will learn more about bioluminescence, why it occurs, and how science has used it to study disease and create fashionable pets.

What is Bioluminescence?

These glowing waves are caused by bioluminescent microorganisms.
Photograph of bioluminescent wave.

Glowing ocean waves are one of the many wondrous sites that our planet has to offer. They have been spotted all around the globe in places such as California, Jamaica, Australia, Japan and the United Kingdom. This incredible display is the result of bioluminescence.

Bioluminescence is a chemical reaction that produces light in a living organism. (The word originates from the Greek word bios, meaning ''life'', and the Latin word lumens, meaning ''light''. Lumens is also the origin of the word ''illuminate''.) Since bioluminescence produces very little heat, it is referred to as cold light.

Most bioluminescent species, such as fish, jellyfish and squid, reside in the oceans. Some naturally occurring bioluminescent organisms, such as fungi and insects, live on land. And, recently, genetic engineering has created a collection of bioluminescent mammals, including mice, cats, and monkeys.

Purpose in Nature

Sure, bioluminescence is pretty for us to look at, but what does it do for the creatures, themselves? As it turns out, bioluminescence serves many possible functions including hunting prey, defending against predators and attracting mates.

Hunting Prey

Bioluminescence can be used as a lure to capture prey. Perhaps the most famous example of this is the anglerfish. Anglerfish, named for fishermen who use a line and hook, live in dark, deep-sea environments. They have a long appendage on their head that ends in a round, bioluminescent organ. Smaller fish are attracted to this light and the anglerfish snap up their meal with their extra-large jaws. You may remember seeing one depicted in Finding Nemo.

The bioluminescent larvae of the fungus gnat attract prey which become trapped in their sticky feeding lines.
Glowworm Caves in New Zealand.

Another example of bioluminescent predation is found in the Glowworm Caves in New Zealand. The ceilings of the Waitomo Caves are draped with what appears to be glowing tinsel. The ''tinsel'' are actually sticky, feeding lines excreted by thousands of bioluminescent larvae of the fungus gnat. The glow of the larvae lures their prey which then become caught in the snares like flies in a spiderweb.

Defending Against Predators

Bioluminescence can be used to hide from or to intimidate predators. Many oceanic predators hunt from below, looking up for the shadows cast by their prey. The hatchetfish have many bioluminescent organs along their belly. These organs produce a blue light that matches the sunlight coming through the water from above. The hatchetfish can change the intensity of this light so that it exactly blends with the sunlight above making the fish nearly invisible from below. This process of using bioluminescence to blend in with a lit background is referred to as counterillumination.

The railroad worm is able to turn its lights on and off in order to startle and confuse its predators.
A photograph of the glowing railroad worm.

The railroad worm also uses bioluminescence defensively. Named because it resembles the lighted windows on a train, the railroad worm is the only insect that glows in two colors, yellow on the body and red on the head. When the larvae of this beetle is approached by a predator, it turns on the red lights on its head to startle and confuse the aggressor.

Attracting Mates

Adult fireflies, or 'lightning bugs', common in the eastern United States, use bioluminescence to attract mates. The last two segments of their abdomen flash on and off to alert the opposite sex of their presence.

Bioluminescence in Mammals

If you have ever wanted a glow-in-the-dark pet, your dreams have come true. Though bioluminescent mammals do not occur in nature, scientists, via genetic engineering, have created glowing mice, dogs, monkeys and more. But before you reprimand them for playing god, these animals were not created just because they are fun to look at.

GFP, or green fluorescent protein, glows a bright green when it is exposed to ultraviolet light, also called black light. It was first isolated from bioluminescent jellyfish in 1962.

Photograph of genetically engineered, glowing mice.

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