Those liver-flavored honey mushrooms I’ve been telling you about — Armillaria complex, common around here — glow in the dark. Not the fruiting bodies, but their root-like rhizomorphs. So do the fruiting bodies of various species of delicate little Mycena mushrooms. And the well-named jack-o’-lantern mushrooms, Omphalotus, which Madison has plenty of, and various other fungi that are busy consuming rotting wood.
I have always loved the bioluminescence. Who wouldn’t? In the Chesapeake Bay, I dove into black water only to be surrounded by the green glow. On Coronado Island off San Diego, the waves crashed green and any disturbance of the sand, e.g. throwing it at someone, produced a brief, exciting flash. And in central Africa, a fungal glow kept me company on a fearful dark night when I was stuck in the forest.
A brief biology lesson.
“Bioluminescence,” said Prof. Kim Coder, in a 1999 explainer, “is the reverse of photosynthesis.”
In photosynthesis, a living organism captures light and carbon-dioxide (CO2) to make organic materials and release oxygen. In bioluminescence, light and carbon-dioxide (CO2) are released by breaking apart organic materials using oxygen.
It seems a fungus goes and loads up a molecule, luceferin (“fire carrier”), with extra energy; then, in the presence of oxygen and the enzyme luciferase, the luceferin decays into its lower-energy self. On the way a photon escapes—voila: light.
Luceferin and luciferase are just generic terms for the reaction, which happens all over nature, and scientists often don’t know exactly what the molecules are. In fact, only the need for oxygen is common to all of them.
Why glow? Maybe, in the case of glowing fruiting bodies, to attract animals that will move the spores. Or maybe, on the other hand, the glow scares off potential predators. Maybe, as Desjardin et al suspect (in this informative 2008 review of fungal bioluminescence), it’s just a byproduct of a reaction that cleans out the oxygen free radicals that, as the beauty-product commercials keep reminding us, damage tissues. Or maybe it’s just a way to bleed off extra energy, like a mushroom’s answer to running around the block.
On a related note, winning the prize for Best Argument for Genetically Modified Food: Wouldn’t these glowing pigs make the best Halloween bacon ever? I know, I know — totally different bioluminescence, pigs with jellyfish DNA. But just think about it.