Bioluminescence seems almost like magic.
Organisms have evolved the ability to produce light for different reasons: to trick predators, to attract mates and even to communicate. The diversity of creatures with this ability is equally astonishing, from the common firefly to deep-sea dwellers that are rarely seen by humans. What's also fascinating is that many of these creatures are not closely related, and bioluminescent traits have evolved separately at least 30 times.
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, as you can see in the image below. They belong to the Lampyridae family, and there are 2000 species around the world, many of which have distinct flashing patterns.
Although Lampyridae larvae are also sometimes called glowworms, there's also distinct family of bioluminescent insect: Phengodidae. This glowworm is found in both North and South America, and has a series of organs that emit light.
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's highly toxic. Motyxia defends itself by oozing cyanide, but the light tells predators to stop before they take a bite.
A new species of glowing millipede was recently discovered on Alcatraz Island.
Most bioluminescent creatures are found in the ocean, often at depths below the reach of sunbeams. Some species of comb jellies, or Ctenophora, are an example of this. The comb jelly produces blue or green light, but the movement of its combs can scatter the light, producing a rainbow effect (see top image). Researchers think the lights may serve to confuse predators.
The bobtail squid has formed a symbiotic relationship with bioluminescent bacteria. The glowing bacteria helps the squid camouflage itself at night, in exchange for food. The bacteria lives under the surface of the mantle, which can act as a filter to control the brightness of the light.
The name "Lanternfish" may be given to any number of fish species belonging to the Myctophidae family. According to researchers at UC Santa Barbara, the fact that each species has a specific pattern of light organs suggest that luminescence helps these fish to attract mates. The lights may also serve as defensive camouflage.
This video illustrates the different species of lanternfish:
The long protrusion on anglerfish's head is called a lure, and it does exactly what it sounds like. The light on the tip of the lure attracts prey right to the fish's toothy mouth, just like in "Finding Nemo." It's no wonder Jeff Kart called this predator a fish to inspire nightmares.
Also like the video, anglerfish often also have bioluminescent patches on other parts of their bodies. However, researchers from UC Santa Barbara point out that these fish have milky eyes only when dead. You can see a living one here, along with other photos of glow-in-the-dark fish.
Most types of krill, tiny shrimp-like creatures, are bioluminescent. Their light-emitting organs are driven by an enzyme reaction. Krill light up when touched or agitated, and are responsible for the amazing effect of glowing waves that can be seen in the wonderful video below, along with some other luminous sea creatures.