A firefly sits on a blade of grass. Photo: James Jordan / CC BY-ND 2.0
One June evening you’re walking along the sidewalk next to a park, or perhaps you’re just in your backyard. Suddenly, you see a small point of light blink on and off. Did that just happen? You look again just in time to see another flash. You slowly realize what you saw: a firefly.
The animal kingdom is full of creatures that use light to their advantage; even humans have a very faint form of bioluminescence, light that is caused by a chemical reaction that occurs inside (or is released by) an organism. Most creatures use their flashy displays to attract mates, lure food or ward off predators, so it’s a desirable trait. It’s estimated that bioluminescence evolved separately at least 30 different times.
But which of these critters shines the brightest? Which shines the longest? We’ve looked at some of the coolest of these organisms in nature.
A headlight beetle found near the Cerro de San Gil Reserve in Izabal, Guatemala. Photo: Adrian Tween / CC BY-NC-SA 2.0
Top Insect- Headlight Beetle
Fireflies aren’t the only insects that light up summer nights. The title of brightest insect, according to a study by Hazel C. Levy at the University of Florida, goes to the headlight beetle, also known as the fire beetle, click beetle, or the “Cucujo” beetle. Unlike fireflies, which blink patterns in the night sky, this beetle emits a continuous blue-green light from three locations on its body— two near its head and the other on its abdomen, which is only visible while it flies. They’re found in the tropical areas of the Americas, including the Caribbean, and grow up to 1.75 inches in length.
The "milk sea" in a composite satellite image, and the region of the Indian Ocean off the coast of Somalia where it was spotted by the Defense Meteorological Satellite Program. Photo: Steven Miller, Naval Research Laboratory
Top Bacterium- Vibrio habreyi
Those spaceship-like organisms called dinoflagellates aren’t only known for the red tides they cause; they’re also known for a blue-green sparkle when disturbed by motion. A different ocean-going organism, however, has hit the top of our list— a small bacterium, Vibrio habreyi, discovered in the Indian Ocean has caused quite a stir recently. It creates the nighttime phenomenon known as milky seas— a pale blue, continuous glow which seems to light up the entire ocean while it lasts (one instance lasted at least three nights). Four hundred years ago, sailors noted this phenomenon, but it wasn’t until recently that satellite imagery traced the source to these tiny, bioluminescent bacteria.
Top Fish- Flashlight Fish
One of the brightest lights in the sea, the flashlight fish possesses two large organs beneath its eyes that contain bioluminescent bacteria. Travelling in large schools, the flashlight fish use their lights in order to confuse predators at night: they blink on and off while swimming in different directions.
Glowing mushrooms at the Sentosa Flower Show in 2011. Photo:hslo / CC BY-SA 2.0
Top Fungus-Neonothopanus gardneri
This highly poisonous mushroom was first discovered in 1840 by an English botanist named George Gardner. It wasn’t until 2005, however, that the mushroom was spotted again. Two scientists from Sao Paulo University and the University of Georgia were studying monkeys in Brazil when they noticed glowing mushrooms at the base of a palm. In an interview by USA today, Dennis Desjardin, a professor at San Francisco State University, says “It glows more brightly than almost all other luminescent mushrooms.” In fact, the shroom’s green hue is so bright that if you held it up to a newspaper, you could read it in the dark.
The deep-sea scyphozoan jellyfish, Atolla wyvillei, as seen under white light. Photo: Edith A. Widder, Operation Deep Scope 2005 Exploration, NOAA-OE.
Top Jellyfish- Atolla Jelly
While the comb jelly (although technically belonging to the phylum, Ctenophora) wins on our list for having the most colorful lights, the atolla jellyfish probably wins for being the brightest. The jellyfish is found in the deep ocean and possesses a red-brown hue, the right color for hiding in waters where little light on the red spectrum reaches. But when threatened by a predator, the atolla jellyfish lights up in a display that can be seen for three hundred feet beneath the waves. The circular, moving light is called a “burglar alarm” by scientists from the NOAA, and is theorized to attract larger predators that might eat the one trying to eat the jellyfish.