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When you think of bioluminescent organisms, you’ll probably imagine the creatures of the deep ocean. But there are other living things, like fungi that also have this incredible ability to emit their own light source.
Why are Some Fungi Bioluminescent?
Bioluminescent fungi are usually found in temperate and tropical environments, and it’s thought that there are 112 species belonging to the Agaricales order, which includes the Omphalotaceae, Mycenaceae, and Agariceae families. These fungi typically emit a green or blue colored glow, although some are brighter with a yellow or orange light.
But the question is, why and how do these fungi produce their own light source? There are many reasons for this, including attracting insects, which will then spread the spores of the fungi, enabling reproduction, similar to pollination in flowering plants. Interestingly, there are some bioluminescent fungi whose glow isn’t limited to the main body or cap but actually extends through the mycelial network to enhance its glow and get it noticed by a greater number of insects.
What’s more, being lit up in the darkness could serve as a warning to potential predators telling them to stay away. However, since this would only be effective in low-light conditions, it’s amazing that most fungi with this ability are found in darker environments.
It is also suggested that some of the chemicals emitted during the bioluminescent process could act as a deterrent to predators, further protecting the mushroom.
Many bacteria species are able to produce their own light and in order to do this, they have to produce a compound known as luciferin. This chemical reacts with oxygen, and the result is the production of light. If fungi cannot produce luciferin by itself, it is suggested by scientists that they may form some sort of symbiotic relationship with luciferin producing bacteria.
Of course, there are many fungi species that have this ability because of their genetics, but this varies between species.
What’s really interesting is that bioluminescent fungi have a circadian rhythm, much like humans. For a long time, scientists believed that these mushrooms would glow all the time. But during studies, using a light-dark cycle, it was observed that they turn on and off according to the light conditions, and this was set to a 22 hour cycle. Even more fascinating was that when temperature was brought into play, the fungi would adapt their circadian rhythm to a more human-like 24 hour cycle.
Types of Bioluminescent Fungi
As I have mentioned, there are well over 100 known species of bioluminescent fungi. While I couldn’t possibly list them all in a single article, I’d like to introduce you to some of the most fascinating.
1. Ghost Fungus (Omphalotus nidiformis)
The ghost fungus is a large, gilled mushroom that grows up to 12 inches (30 cm) and is typically found on mainland Australia and the neighboring island of Tasmania. It takes its name from the green/blue glow that illuminates its unique shape, giving it the appearance of a ghost. But while it might look beautiful, this is a toxic species that can cause stomach upset if consumed.
This species is usually found in wooded areas, especially on rotting wood, such as fallen logs or tree stumps. At night, when the light is low, these beautiful fungi glow and since they usually grow in clusters, they’re quite the sight to behold.
Ghost fungus is able to produce its own luciferin, and while it’s not confirmed as to why it glows, some suggestions were made that it has something to do with attracting insects to disperse spores. Other studies dispute this claim, saying that the glow is more likely a metabolic byproduct.
2. Night Light Mushroom (Mycena chlorophos)
The night light mushroom is found across subtropical Asia and usually prefers growing on rotting wood or among the leaf litter on the forest floor. While beautiful when aglow, the night light mushroom is not a large species and only grows to around 0.4 – 1 inch (1 – 2.5 cm) in diameter.
The caps are usually brownish in color and sit on stems that can measure up to 1.2 inches (3 cm) in length.
During the night, these mushrooms provide an impressive green glow which is how they got their name, but we still aren’t 100% certain as to why they are bioluminescent. Scientists think that it could be to do with insect attraction or as a warning to predators.
3. Honey Fungus (Armillaria mellea)
The honey fungus doesn’t grow on already rotting wood, like the species I have discussed so far. It’s actually a parasite that causes the decay of healthy wood and is found on woody plants, and has the ability to attack the roots. Sadly, by the time the fruits are visible, it’s too late and the tree or plant has already suffered more than it can tolerate.
Still, while it’s a nuisance for plants, it’s still one of nature’s most beautiful creations and emits a pale blue or green glow in low-light conditions. What’s interesting is that the intensity of the glow and its color varies according to environmental factors like temperature.
Honey fungus is found in most temperate areas and is considered a problem for gardeners owing to its preference for broadleaf and coniferous plants. However, it is edible although some people are sensitive to it and may experience mild stomach upset.
4. Bitter Oyster (Panellus stipticus)
The bitter oyster is found in many places around the world including North America, Europe, Asia, and Australia, where it typically grows on decaying wood. When the light conditions are low, this species emits a faint green glow, and what’s interesting is that the entire fungus lights up, mycelia, cap, gills and all!
It has been observed that the bitter oyster glows most intensely when the spores are about to mature, suggesting that it produces luciferin and therefore light as a way of attracting spore-dispersing insects.
Since bitter oyster is found on decaying wood, it plays an important role in the decomposition of this natural material. While you may be able to eat bitter oyster mushrooms, you probably wouldn’t want to as they have an unpleasant taste and tough texture. That said, there are reports of the mushroom being used as a blood thickening agent.
5. Jack-O’-Lantern Mushroom (Omphalotus olearius)
With a name like the Jack-O’Lantern mushroom, it’ll come as no surprise that this is a deep rusty orange-colored mushroom. However, when it glows, the light is a more green to yellow color and is emitted from around the edges of the cap as well as the gills.
Jack-O’-’Lantern mushrooms are found in the woodlands of Europe, although there are some reports of clusters growing as far south as South Africa. The cap has a slightly concave center and can grow up to 4.7 inches (12 cm) in diameter.
This species prefers to grow on hardwood but has a certain affinity for olive trees. Identification is crucial when foraging as this species is toxic but is often mistaken for the chanterelle mushroom, which is edible.
6. Eternal Light Mushroom (Mycena luxaeterna)
The eternal light mushroom is an interesting species with a long stem and parachute-shaped cap. They are tiny in size, with the caps only growing to around 0.8 inches (2 cm), and have one of the smallest distributions of all fungi, only growing in a very limited area in the São Paulo Atlantic rainforest.
Eternal light mushrooms emit an otherworldly green glow along the entire fruit body and stem. What’s unique about them is that, unlike other species that only glow in low light conditions, the eternal light mushroom, as its name suggests, is glowing 24 hours a day!
Being so small, these mushrooms are easily able to grow on twigs and sticks. They’re not toxic although, owing to how rare they are, they’re not commonly eaten by humans or used in cooking.
7. Heavenly Light Mushroom (Mycena lux-coeli)
Not discovered until 1954, the heavenly light mushroom is found on the islands of Japan, where several other species of bioluminescent fungi are also found.
This species is usually found on fallen chinquapin trees and is able to produce its own luciferin to create a bright green glow in low-light conditions. While it isn’t confirmed as to why the heavenly light mushroom glows like this, it’s more than likely to do with attracting insects, scientists suggest.
While they may be difficult to spot during the day, since the caps are no more than 0.8 inches (2 cm) in diameter, they light up the forest at night, especially during the rainy season.
8. Flor de Coco (Neonothopanus gardneri)
Flor de Coco is an interesting-looking species of bioluminescent mushroom found in very limited areas of Brazil. While it was initially discovered in the 1800s, it was rediscovered back in 2005 and was noted for glowing much more brightly than other species.
The cap of this Flor de Coco can grow up to 3.5 inches (9 cm) in diameter and has a yellow to cream center with much darker coloration around the edges. You’ll typically see them growing around the base of palm trees, which is why it is sometimes called the coconut mushroom. The Flor de Coco plays an important role for these trees, breaking down decaying wood and ensuring healthy nutrient cycling.
Interestingly, scientists have been looking at the glow pattern of this species and have concluded that it follows the circadian clock. It’s also a close relative of the Jack-O’-Lantern mushroom.
9. Fairy Bonnets (Mycena illuminans)
The name fairy bonnet would lead you to believe that this is a rather cute and charming species of bioluminescent fungi, and you wouldn’t be wrong. They’re well-loved because of their tiny bell-shaped caps and the soft blue-to-green glow they emit in low-light conditions.
Fairy bonnets are typically found growing on the forest floor or on decaying wood and are primarily found on the Indonesian island of Java.
It is thought that fairy bonnets emit light as a way of attracting insects to disperse their spores. On top of this, it’s believed that their bioluminescence acts as a form of protection from anti-oxidants from wood decay.
What is the Difference Between Bioluminescence & Biofluorescence?
Bioluminescence and biofluorescence are both ways that organisms emit naturally produced light. However, it’s important to keep in mind that they are two separate and unique processes.
One of the best ways of looking at it is that bioluminescence occurs as a result of the organism itself producing the light, while biofluorescence is created by the absorption and re-emission of light.
During bioluminesce, a chemical reaction takes place involving enzymes that produce a chemical called luciferin. When this reacts with oxygen, light is produced. On the other hand, biofluorescence happens when an organism absorbs UV light, blue light, or another source and emits this from its body. Where bioluminescence requires a certain amount of energy from the organism, biofluorescence does not.
Biofluorescence could be compared to one of those glow in the dark toys. When light shines on the toy, it is re-emitted at a different wavelength, producing a glow; this works the same in nature, although scientists aren’t 100% sure as to why some organisms possess this biofluorescent ability. However, it is thought that it may have something to do with camouflage and is seen in various creatures such as fish, marine invertebrates, and even the reefs on which they live. When biofluorescence happens, the light can be displayed in various colors, and the emitted light is often much brighter than the light that caused it.
With bioluminescence, the function is much better understood and can range from serving as a predatory warning or attracting prey to communication and attracting a mate. In any case, different creatures emit different colored lights, but this largely depends on what chemicals are involved in the process. You’re probably familiar with the firefly, which is one of the most well-known bioluminescent creatures, but other examples include deep sea fish, jellyfish, and of course, the fungi we have looked at in this article.