The tropical forests of Northeaster Brazil have their own nightlight: a peculiar mushroom called Neonothopanus gardneri that glows in the dark. Like a street light, it’s tuned to activate its bioluminescence only in the dark, first in the twilight then peaking at about 10 PM. Researchers at Dartmouth College in the US and the University of São Paulo in Brazil have now fond out what this strange behavior is all about: ‘candy’ for insects.

Neonothopanus gardneri  in action. Photo: Flickr Creative Commons

Neonothopanus gardneri in action. Photo: Flickr Creative Commons

The Brazilian variety isn’t alone. According to Jay Dunlap, a geneticist and molecular biologist at Dartmouth’s medical school, there are 71 discovered species of glow in the dark mushrooms. This might seem like a lot, but considering there are about 5 million mushroom species in the world, these lonesome fungi are quite rare, nevermind spectacular. The  bioluminescence relies on chemical processes inside the mushrooms’ cells which can show up right about anywhere:  the fruiting body, the thready web-like mycelium and even in dispersing spores.

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Many of the bioluminescent fungi time their glow around the evening, so as not to waste the energy for nothing during daytime when the sun’s rays conceal the glow. This suggests that this phenomenon is no evolutionary fluke. What’s its purpose, though? The researchers suspected the glow in the dark attracts insects, which like we all know to our own annoyance are highly attracted to light. Fungi of course do not eat insects; they exploit them in another way: to spread their spores among the forest.

To test this hypothesis, the team made some fake glow in the dark mushrooms by placing LED lights underneath them. Sticky tape was put on the mushrooms to trap the insects. At the end of the day, they counted the number of trapped insects by the fake fungi compared to normal fungi, with no LED lights or bioluminescence capability.  A lot more flies and other jungle insects were found in the sticky tape from the fake mushrooms, according to the paper published in Current Biology.

What’s interesting is that the mushrooms peaked at exactly 10 PM, suggesting a highly accurate internal biological clock regulates the bioluminescence. Brazilian researcher Etelvino José Henriques Bechara jokingly says “If he lived [among the mushrooms], he could use the light intensity to tell time.”