Why Glowing Mushrooms Light Up a Forest

If you've ever taken an evening hike, you may have seen them: mushrooms that are a little brighter than they should be in the failing light. Thousands of years ago, Greek philosophers called this "cold fire" as the light emanated from decaying wood, but today's scientists know better. It's bioluminescence, and researchers are revealing how and why exactly some mushrooms have it.

A just recently published study in the journal Current Biology details how glowing mushrooms may have developed the trait in order to attract insects. These insects then may unknowingly help spread the mushrooms' spores throughout a forest.

"Our research provides an answer to the question, 'Why do fungi make light?' that was first asked, at least first asked in print, by Aristotle more than 2,000 years ago," biochemist Cassius Stevani of Brazil's Instituto de Química-Universidade de São Paulo told Reuters.

Unlike other species that may use this glow to attract prey, communicate, or simply see in dark environments, this may be the first time bioluminescence is specifically used to help a species colonize new habitats.

So how was this determined? Stevani and his colleagues took a special look at Neonothopanus gardneri, which grows around the bases of young coconut palm trees in Brazilian forests.

According to the researchers, this was the biggest and brightest of the 70-or-so species of mushrooms that have a "cold fire" glow.

They found that a temperature-controlled circadian clock in the mushroom regulates when it glows, causing it to only show at night. This, the researchers suggest, implies that the glow has a specific purpose, and is not simply a random consequence of chemistry.

The researcher then set out to find just how many insects these mushrooms are actually attracting. They fashioned together several pseudo-mushrooms with a relatively similar glow (achieved through LED lighting). The fake mushrooms trapped all the insects drawn to them over the course of the night, revealing that the glow does indeed attract everything from flies, to snails, to harvestmen.

When these organisms realize that there isn't actually any food or other attractions near this light, they eventually wander away, spreading the 'embers' (spores) of cold fire wherever they chose to venture next.

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