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Outside/Inbox: How does bioluminescence work?

A bioluminescent jelly at the Monterey Bay Aquarium.
Credit: Chris Favero (CC BY-SA 2.0 DEED)
A bioluminescent jelly at the Monterey Bay Aquarium.

Every other Friday on Morning Edition, the Outside/In team answers a question from a listener about the natural world.

This week, Doug called in from Elk, Washington, to ask a question about how fireflies create their iconic glow.

“Is the bioluminescence that they produce in their butts… the same as the bioluminescence in the ocean?

All the light you cannot see

If you’ve ever had the privilege to walk through a field of fireflies at dusk, or witness a swirl of sparkling blue algae light up the ocean, you know how magical and rare bioluminescence can seem.

But it turns out, underwater at least, the ability to produce light is less an exception and more of the rule.

Deidre Gibson is chair of the Department of Marine and Environmental Science at Hampton University, an HBCU in Virginia

“Bioluminescence… is perhaps the most common form of communication in the deep ocean,” she said.

Think about it. Most of the ocean - about 80% - is completely devoid of natural light. Scientists estimate about three-quarters of all marine organisms exhibit some form of bioluminescence to compensate.

And the vast majority of those organisms – along with land bioluminators, like fireflies and some species of fungi – are all using the same basic chemistry set to do it.

How to get a glow-up

Whether we’re talking about flashes of yellow light from a firefly’s butt (technically, it’s lower abdomen) or the blue glow of an offshore algae bloom, most bioluminescent reactions stem from the same chemical ingredients.

One is an enzyme called luciferase, and the other is a naturally occurring molecule called a luciferin (In case you’re wondering, Lucifer - the devil - translates to “light-bringer” in Latin).

When a luciferin gets excited (typically, in the presence of oxygen) it reacts with the luciferase and the ensuing reaction emits a photon of light.

Glowsticks work using the same principle. One chamber holds a variety of luciferin, the other chamber contains a chemical that acts like luciferase. Snap the tube, give it a shake, and the two combine to produce a bright glow.

One important quality that differentiates this process from many other light-emitting chemical reactions (like combustion) is that bioluminescence produces very little heat.

A composite image reveals the path of wandering fireflies.
Bernd Thaller (CC BY 2.0 DEED)
A composite image reveals the path of wandering fireflies.

Let there be light

Even though the mechanism that makes bioluminescence is shared by fireflies and fungi, algae and bacteria, as well as squids, cuttlefish, and more, many of these organisms have evolved to use that light in different ways.

Some use light to attract potential mates, others to lure in an unsuspecting meal. It’s also an essential tool for evading predators.

“Bioluminescence can include what we call counter-illumination camouflage,” Gibson said.

The firefly squid is one example. It produces light from its underside to blend in with light from the ocean surface, rendering it near invisible to predators swimming below.

Some animals that can’t produce their own light have symbiotic relationships with organisms that can. The light produced by anglerfish, for example, comes from bacteria housed in their lures.

There’s even a type of starfish (the brittle star) that – when under threat from a pursuing predator – can detach a bioluminescent limb while the rest of the body slips away unseen in the dark.

These are only a handful of the wild examples we know about. Remember, most of planet Earth exists beyond our vision - in complete darkness. Who knows what wild and creative bioluminescent creatures are out there?

Submit your question about the natural world If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to You can also leave a message on our hotline, 1-844-GO-OTTER.Outside/In is a podcast! Subscribe wherever you get yours.

Taylor Quimby is Supervising Senior Producer of the environmental podcast Outside/In, Producer/Reporter/Host of Patient Zero, and Senior Producer of the serialized true crime podcast Bear Brook.
Outside/In is a show where curiosity and the natural world collide. Click here for podcast episodes and more.

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