In nature, few things catch our attention in the same way as bioluminescence, the production and emission of light by a living entity. Whether it’s mysterious lifeforms down in the darkest depths of the ocean, or twinkling fireflies dancing through warm twilight meadows, the near-magical quality of seeing a bioluminescent organism is mesmerising.
Despite the many ways in which we encounter bioluminescence, there are no plants which have taken on the adaptation truly. However, the fungal kingdom more than makes up for where they are lacking.
Bioluminescence in fungi usually comes in yellow-green or greenish-blue shades.
Toadstools with tricks
Fungi are unusual enough without adding the spice of lighting-up after dark. Whereas science has been able to identify the reasons for bioluminescence in many animals, whether for hunting (as in angler fish) or mating (as in glow worms), the reasons fungi use it are vague.
Studies into the purpose of bioluminescence have drawn no solid conclusions. Some studies have shown that the light draws in nocturnal insects to disperse the spores. Contrastingly, other studies have shown it to have no effect at all. It is even suspected by some scientists that the spectral light deters would-be grazers from eating the mushrooms.
Mycologists have also theorised that the light is merely a bi-product of the fungus metabolising decaying wood.
What we usually see of the fungus is just the fruiting body of a much more extensive network of root-like mycelia, as seen here.
Glowing fungal folklore
Whatever the reasons, glow-in-the-dark fungi are pretty amazing. They also have a certain eerie quality to them. With names like ghost mushroom and bleeding fairy helmet, it is no wonder that folklore developed around them. Sinister spirits such as jack-o’-lanterns, or will o’ the’ wisps were thought to lure innocent travellers into forests at night with their eerie glow. These lights are occasionally called fairy fire.
Apart from phantom fungi, natural gasses can cause the phenomenon once labelled as will o' the wisps.
In Australia, Scottish naturalist James Drummond noted that when aborigines looked upon a glowing ghost fungus, they began to call out chinga, a local word for spirit. Bioluminescence in fungi eventually developed its own name: foxfire. The exact origin of the term foxfire is foggy, and it is thought to have most likely originate from the Old French word fols, meaning false.
Foxes share the wooded habitats in which these fungi grow, and they are also linked to the lights in some Far Eastern folklore.
Bleeding fairy helmet is so named for the red sap produced when damaged (and because they do look like fairies’ helmets!).
The science behind foxfire
The first recorded documentation of foxfire was by Aristotle in the third century B.C. He remarked that the light was cold to the touch. Bioluminescence is now considered a ‘cold light’; a light where less than 20% of the light generates thermal radiation.
Thanks to the 19th-century French chemist Raphaël Dubois, scientists now know this light is produced by a class of oxidative enzymes known as luciferase. This luciferase must combine with luciferin to create the eerie glow associated with bioluminescence.
It is these same compounds which also create the light associated with fireflies and some deep-sea creatures. Fungal bioluminescence, however, follows a temperature-compensated circadian clock, which is thought to help the mushrooms save energy.
If you’re wondering why the components are named ‘luciferase’ and ‘luciferin’, it’s nothing satanic, but from the Latin ‘light-bringer’.
Although there are estimated to be over three million species of fungi on the planet, – that’s even more than species of plant – only around 80 of these are bioluminescent. All of them are gilled mushrooms (Agaricales).
It is the species which feed on decaying wood/plant matter (known as white-rot fungi) that produce light. Of these, the honey fungus Armillaria mellea is most common, with a wide distribution across North America.
Other species are found on rainforest floors in South America and Africa, as well as across Europe and Asia. Here are some of the more remarkable species:
Jack O’ Lanterns (Omphalotus olearia & O. illudens): although a rarity, Jack O’ Lanterns can be found in the U.K., although they are more common in North America. The glow is very dim and appears beneath the gills of this poisonous toadstool. The Australian O. nidiformis, commonly known as the ghost fungus, is an antipodean cousin.
The lurid glow of the jack o' lantern
Bitter Oyster (Panellus stipticus): Although it grows in the U.K., it is only the North American strain which glows at night. The fungus can be found growing around birch, oak and beech trees and is also known as the astringent panus or luminescent panellus.
Honey fungus (Armillaria mellea): Many gardeners will be very familiar with honey fungus, and some species can be a real problem as they parasitise trees.
Flor de Coco (Neonothopanus gardneri): Another Brazilian native, the flor de coco feeds on rotting palm material. The fungus is named after the English botanist George Gardner, who discovered it when he saw children playing with the glowing mushrooms in the streets and thought they were fireflies. The name means coconut flower, due to the way they sprout from the trunks of palm trees.
The striking difference between how the eternal light mushroom appears during day and night.
Eternal light mushroom (Mycena luxaeterna): A spooky native of Brazil with luminous green mushrooms where only the stem, or stipe, glows. There are also many other Mycena species which produce brightly-glowing mushrooms, including the vivid Japanese M. chlorophos and the dimmer bleeding fairy helmet.
Foraging for fluorescence
Heading out and trying to find bioluminescent fungi is not a reasonable prospect for most. The few species which do occur in the U.K. are scarce and often so dim that it requires a great deal of patience on a moonless night to see them.
You would need to spend a while adjusting your eyes to the dark environment if you wanted to spot the dim glow. Even then it would be a struggle.
The candlesnuff fungus, which looks like a burnt, ashy candle wick, is so nominally bioluminescent that it is barely noticeable. If travelling somewhere where species are more easily spotted, (such as North America or Australia) you are better off identifying them during daylight and returning in the evening.
Fungi are vital to the forest ecosystem, breaking down cellulose and playing a key part in the carbon cycle.
A crepuscular supper?
It’s worth mentioning here that you should never eat wild mushrooms without doing your research first. Many of our native species delight in names such as ‘destroying angel’, ‘death cap’ and ‘the sickener’ for good reason. The bioluminescent species I’ve listed here are non-edible or poisonous and should not be consumed.
The archetypal mushroom, the fly agaric, is also a poisonous native species and although beautiful by day, it does not glow at night like some of its cousins.
A far more practical way to discover bioluminescent fungi is to grow your own at home. You will find many suppliers online with available growing kits and instructions to guide you on your way. The most commonly seen species seen for sale are Omphalotus and Panellus.
All come with full instructions and usually rely on supplying a growing medium (often a log, ‘cake’ or grow bag) which you then keep in a sterilised, damp environment. The fungus’s root-like mycelia are also bioluminescent. These colonise the medium before sending up fruiting bodies, which usually takes less than a month.
Although grown more as a curiosity, if you set up a small terrarium you could make a little feature – a real talking point among your friends!
Here's an example of a grow-your-own mushroom kit, this time for the edible shiitake mushroom.
Mankind and the glowing mushroom
In the early 19th century, naturalists discovered bioluminescent fungi growing on the wooden beams used to support mines, deep below the ground. Interestingly, this ability to light up a man-made environment is also something that hits close to home today.
Recent research in Siberia managed to break down the components of bioluminescence in fungi. They discovered that fungal luciferin is chemically unrelated to other luciferins, representing an entirely different mechanism of light emission. Most importantly of all, it is compatible with plants.
Now scientists are looking into genetically modifying trees to luminesce, offering a sustainable alternative to street lamps. Although the idea sounds like something from science fiction, it may not be as absurd as initially thought, with the Glowing Plant Project being the first successful crowd-funding campaign for synthetic biology application.
Fungi are actually more closely related to humans than plants, having broken away from them on the genealogical tree around 1.1 billion years ago. Panellus strictus pictured.
- Because of the conditions in which you would typically see bioluminescence, such as a midnight forest or ocean deep, the light appears bright. However, it is relatively dim. That said, certain species are bright enough for you to read by – just about!
- Foxfire was used to light the barometer and compass needles of the ‘Turtle’ submarine in 1775, also known as the ‘American Turtle’. This was the first recorded submersible with a recorded use in combat and was used during the American Revolutionary War. Benjamin Franklin was a consultant on the matter and George Washington funded it.
- Feel as though you might recognise glowing fungi from your own or your child’s youth? That's because you probably do. The meeting spot in Disney/Pixar’s A Bug’s Life is a bioluminescent mushroom, and they also light up the underground world in Dreamworks’s Antz.
- After Aristotle’s original notes on bioluminescent fungi in 382 B.C., the next mention is from Roman thinker Pliny the Elder, who saw the intriguing glowing toadstools growing in an olive grove.
These black bootlaces are the parasitic rhizomorphs of honey fungus and will be well-known to some gardeners. It is these which form the ‘humungous fungus’.
- The bioluminescent honey fungus mentioned above, A. mellea, is closely related to the parasitic A. ostoyae (A. solidipes). A colony of this mushroom, known as the Humungous Fungus, is argued to be the largest organism on the planet. The genetically identical mycelia fuse to measure a fungus 2.4 miles across (3.8km). It may not glow, but what a title!
- Bioluminescent fungi also appear in many pieces of literature, including The Adventures of Huckleberry Finn, where Tom Sawyer uses them to illuminate a tunnel he is digging.
- Foxfire is also known as chimpanzee fire when it grows in the dark forests of West and Central Africa. It lights up the forest floor at night and was featured in the BBC One series Africa.
- Aside from fungi, other bioluminescent organisms include insects, fish, dinoflagellates (algae), crustaceans, cephalopods (squid), jellyfish, sea pansies and cone jellies.
Although glowing fungi look vivid in photos, they are often enhanced to appear brighter. In reality the lights are usually far more subtle, but still eerie and utterly fascinating.