It might sound like the opening to a trippy fairy tale, but there are now 71 known species of bioluminescent mushrooms that glow night and day amidst the leaf litter of tropical jungles across the globe.

Seven new species of these fungi are described in an early online report from the journal Mycologia's March/April 2010 issue, four new to science and three previously described—sans the shimmer. This news was published online today.

It was a surprise to find so many new mushrooms that give off this glow, says lead paper author Dennis Desjardin, a professor of biology at San Francisco State University, given the tens of thousands of fungi species that do not gleam. Hunting for these tiny beacons can be treacherous, too, as researchers tromp out into tropical forests in disorienting darkness. Indeed, "some environments are a little too dangerous to [collect] them in," Desjardin says. In those locations, he notes, mushrooms are gathered in the daylight and taken back to the lab to observe in darkness and test for light with a photometer.

Joining the 64 previously known glowing fungi species are: Mycena silvaelucens, which glows a yellow-green; Mycena luxaeterna, whose name, meaning "eternal light," was inspired by Mozart's Requiem; Mycena luxperpetua, similar to M. luxaeterna; Mycena luxarboricola, just three to five millimeters in diameter; Mycena abieticola, which had previously been misreported as a different species by the group in 2007; Mycena aspratilis, previously described in 1997 without a glow; and Mycena margarita, which had been known to science since 1916 and grows in the U.S., among other places, but had never been reported to incandesce.

The glowing mushrooms do not signal danger; unlike some other visually distinguishable species, they are not poisonous. "It's not saying, 'Don't eat me because you're going to get really sick,'" Desjardin says of the glowing fungi. So why then do these humble mushrooms go through the trouble?

There are a number of theories floating around: The glow has been found to attract insects, which could pick up spores on their bodies—akin to pollen on a bee—and spread the spores over a wider area than they might otherwise have traveled in a relatively windless forest. Such an explanation, however, may not explain its purpose in species whose mycelium (the digestive rather than spore-releasing parts) glow instead. In that case, Desjardin says, the glowing might attract predators of the bugs that feed on the mushroom, "attracting the enemy of the enemy." A final explanation is that there may not be any evolutionary advantage at all. "They glow 24 hours a day," he says, which means that it "probably has to do with their metabolism of decomposition." So the glow may just be a release of energy—rather than heat—as a waste product.

The answers to these questions may only come with a better understanding of exactly how the glow occurs. Although other bioluminescent creatures, such as fireflies and some plankton, are better understood, researchers have yet to uncover the precise pathways and compounds that make these 'shrooms shine.

Desjardin and his team have been able to extract the two key bioluminescence actors—the luciferin, which produces the light, and the luciferase, which starts the glowing reaction—and mix them in the laboratory to generate a glow. They have even been able to mix them between species and still make a glow, which "is giving us an indication that there's one pathway for luminescence in fungi—or at least they're producing similar luciferin and luciferase across the board," Desjardin says.

These luminescent mushrooms also hail from more than a dozen genetic lineages, leaving Desjardin to wonder if this glow in fact evolved once and most other mushrooms just lost the ability. He and his team are hoping to undertake a genome sequencing project that would compare the genetic makeup of a glowing mushroom with that of a closely related mushroom that does not, which should shed some light on how the process works and when it might have evolved.

In the meantime, the mycologists continue their hunt—and even have a few new species up their sleeves that will soon be described, as well. "We will continue to find a number more, which is always fun," Desjardin says. "And when they end up being completely different lineages, it's always exciting and brings up new questions."