Some mushrooms glow in the dark to attract the attention of insects that spread the fungal spores around, according to scientists who have finally answered a question posed by Aristotle over 2,000 years ago.
Greek philosopher Aristotle was aware of the intriguing fact that some mushrooms glow in the dark but the reason for this remained unknown.
Scientists have now found that the light emitted from those fungi attracts the attention of insects, including beetles, flies, wasps, and ants.
Those insect visitors are apparently good for the fungi because they spread the fungal spores around.
The new study also showed that the mushrooms' bioluminescence is under the control of the circadian clock.
"It appears that fungi make light so they are noticed by insects who can help the fungus colonise new habitats," said Cassius Stevani of Brazil's Instituto de Quimica-Universidade de Sao Paulo.
The circadian control of bioluminescence makes the process more efficient.
Among bioluminescent organisms, fungi are the most rare and least well understood. Only 71 of more than 100,000 described fungal species produce green light in a biochemical process that requires oxygen and energy.
Researchers had believed in most cases that fungi produce light around the clock, suggesting that perhaps it was a simple, if expensive, metabolic byproduct.
Stevani and colleagues studied Neonothopanus gardneri, one of the biggest and brightest of bioluminescent mushrooms.
N gardneri is also called "flor de coco," meaning coconut flower, by locals in Brazil, where the mushroom can be found attached to leaves at the base of young palm trees in coconut forests.
The researchers found that the mushrooms' glow is under the control of a temperature-compensated circadian clock.
To find out what that green glow might do for the mushrooms, the researchers made sticky, fake mushrooms out of acrylic resin and lit some from the inside with green LED lights.
When those pretend fungi were placed in the forest where the real bioluminescent mushrooms are found, the ones that were lit led many more staphilinid rove beetles, as well as flies, wasps, ants, and "true bugs," to get stuck than did sticky dark mushrooms.
Researchers said they are now interested in identifying the genes responsible for the mushrooms' bioluminescence and exploring their interaction with the circadian clock that controls them.
The study is published in the Cell Press journal Current Biology.
