8 Brilliant Bioluminescent Animals

Bioluminescent animals are a wonder of nature. From the common firefly to deep-sea dwellers that are rarely seen by humans, the diversity of creatures that can emit light is astonishing.

What Is Bioluminescence?

Bioluminescence is the production of light by a living organism via a chemical reaction.

Animals and other organisms have evolved the ability to produce light for different reasons: to trick predators, to attract mates, and even to communicate. Interestingly, many of these creatures are not closely related, and bioluminescent traits have evolved separately dozens of times.

Here are eight of the most incredible bioluminescent animals.

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Fireflies

An illuminated firefly with its wings spread wide. — Ali Majdfar / Getty Images

Fireflies, also known as lightning bugs, are one of the most common examples of bioluminescence. They have a special organ that produces light through a chemical reaction. Fireflies use flashing light to attract mates, but begin emitting light even as larvae. They belong to the Lampyridae family, and there are 2,000 species around the world, many of which have distinct flashing patterns.

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Glowworms

A glowworm with a bright green body of light. — Jasius / Getty Images

The glowworm beetle, known as Phengodidae, is a distinct family of bioluminescent insect. Both the female glowworm beetle and the larvae produce light. The glowworm is found in North and South America and has a series of organs that emit light. Female glowworms are sometimes called railroad worms because the lights in their body resemble the cars on a train.

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Millipedes

A millipede with its glowing green body and hair-like legs. — Eden, Janine and Jim / Flickr / CC BY 2.0

The Motyxia millipede, also commonly known as the Sierra luminous millipede, is another bioluminescent invertebrate. In a paper published in Current Biology, researchers report that this millipede's bright light is a warning to predators that it is highly toxic. Motyxia defends itself by oozing cyanide, but the light tells predators to stop before they take a bite.

After a 50-year absence, the millipede Xystocheir bistipita was rediscovered. This species, which is also bioluminescent, is considered an evolutionary sister of Motyxia.

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Comb Jelly

Most bioluminescent creatures are found in the ocean, often at depths below the reach of sunbeams. Some species of comb jellies, or Ctenophora, are examples of this. The comb jelly produces blue or green light, but the movement of its combs can scatter the light, producing a rainbow effect. The light produced by comb jellies can be used to both confuse and attract predators.

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Bobtail Squid

The bobtail squid has formed a symbiotic relationship with bioluminescent bacteria known as Vibrio fischeri. In exchange for food, the glowing bacteria help the squid camouflage itself at night. The bacteria live under the surface of the squid's mantle, which can act as a filter to control the brightness of the light.

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Lanternfish

The name lanternfish may be given to any number of fish species belonging to the Myctophidae family. Lanternfish are abundant deep-sea creatures, with over 250 species. Each species has a specific pattern of light organs. They utilize their bioluminescence to observe prey and predators, for camouflage, and to attract mates.

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Anglerfish

Angler specimen with its prominent "lure" above its head.bioluminescent fish — Masaki Miya et al. / Wikimedia Commons / CC BY 2.0

The long protrusion on anglerfish's head is called a lure, and it does exactly what it sounds like: attracts prey and mates. The bacteria that fills the lure allow this deep-sea fish to make its own light. Only female anglerfish, which are larger, have the special lighted lure. The smaller male anglerfish have a parasitic relationship with the female.

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Krill

Most types of krill, tiny shrimp-like creatures, are bioluminescent. Their light-emitting organs are driven by an enzyme reaction. Near the bottom of the food chain, krill feed on plankton and are the primary food source for many ocean animals. Krill, which travel in great numbers, may use bioluminescence to communicate. These creatures are responsible for the amazing effect of glowing waves that can be seen in the video below.

What Causes Bioluminescence?

The ability to glow seems like a fantastical superpower. How could an animal possibly emit light from its own body on command?

Bioluminescence, it turns out, occurs because of the compound luciferin, which produces light when it reacts with oxygen. This chemical reaction can occur either inside or outside the body.

Even you have luciferin that causes you to glow ever so subtly depending on the time of day, research has found. While technically visible, human bioluminescence is too weak for our eyes to see it.