Source: The Guardian
BY Steve Conner
On a moonless night deep in a Brazilian rainforest the only thing you are likely to see are the tiny smears of light from flitting fireflies or the ghostly glow of mushrooms scattered around the forest floor. Both effects are the result of bioluminescence, the peculiar ability of some organisms to behave like living night-lights.
Bioluminescence has been “invented” dozens of times in evolutionary history and serves a variety of purposes, from attracting mates and luring prey to warding off predators. Its existence in fungi – a rare if not unique case of bioluminescence outside the animal and microbial worlds – has posed more of a mystery. But scientists may now be able to explain not only why certain mushrooms glow in the dark, but how – and in doing so they could be nearer to creating glowing trees as a novel form of street lighting.
Aristotle in 382BC and the Roman scholar Pliny the Elder writing three centuries later both observed the effect of fungal bioluminescence when they described the glowing light of the cold “fire” of damp wood. The ghostly glow later became known as “foxfire”, probably from the Old French word fois meaning “false”, and the phenomenon appeared in many works of literature, including The Adventures of Huckleberry Finn when Tom Sawyer used it to light up a tunnel.
Naturalists in the early 19th century identified fungal growth as the source of the glow from wooden support beams used to shore up mines. Many fungi and mushrooms are now known to glow in the dark, and explanations for why they do it range from it being a useless by-product of metabolism to a sophisticated anti-predator adaptation.
The ghostly glow appeared in The Adventures of Huckleberry Finn when Tom Sawyer used it to light up a tunnel
But the best explanation seems to be that the night-light attracts insects and other animals to the fruiting bodies of fungi, who then spread the spores far and wide. Cassius Stevani at the São Paulo University in Brazil and colleagues showed this by scattering plastic mushrooms on the forest floor fitted with green LED lights that matched the eerie bioluminescence of Neonothopanus gardneri, a splendid mushroom that grows at the base of palm trees. He found the light attracted the sort of insects and other creatures that would be good at spreading spores. They also showed the bioluminescence only occurred at night – ruling out the “useless by-product” theory. “Results indicate that the bioluminescence can attract animals to disperse spores. This additional dispersal mechanism might confer to this fungus some advantage, especially in dense forest,” Stevani says.
The exact method of how mushrooms can generate a spooky glow remained a mystery, in contrast to the elucidation of the light-emitting pigments used by the many other forms of life that can generate bioluminescence.