There's a Humongous Ancient Fungus Growing Beneath Michigan

There's a massive, ancient fungus growing beneath Michigan that is far bigger and older than once believed, scientists have said.

The fungus, named Armillaria gallica, was first discovered in the late 1980s in Michigan's Upper Peninsula. At the time, it was thought to be around 1,500 years old, extended over 37 hectares of forest floor, and weighed over 110 tons. This, scientists said, made it one of the largest and oldest organisms on Earth.

"Nearly three decades on, we returned to the site of individual for new sampling," the team wrote in a study appearing on the preprint server biorxiv.org. "We report here that the same genetic individual of A. gallica is still alive on its original site, but we estimated that it is older and larger than originally estimated, at least 2,500 years and [400 tons], respectively."

When it was first discovered, the media dubbed the A. gallica the "humongous fungus." In the years that followed, it turned out this giant specimen was not all that special and several other humongous funguses were found. "Any temporally continuous forest could support large, old Armillaria individuals. Indeed, at least two other individuals of a sibling Armillaria species have been reported to occupy larger areas than [the humongous fungus]."

Armillaria is successful because it can live as a saprophyte, which live on dead or decaying organic matter, or as a necrotrophic parasite, which kills host plant tissue and takes over. This means they are able to grow across vast areas.

To reassess A. gallica's size, the team used the original study then took 245 samples and linked them to GPS coordinates. From this, they were able to map out exactly how big the fungus had become.

They were also able to examine how the specimen had changed over three decades, looking at the mutations that had taken place over the years. Findings showed the fungus spreads like a cancer, but with an extremely low rate of mutation. Because of this low mutation rate, researchers believe the species could offer some insight into the development of cancer.

"Evolution in cancer occurs on a time span shorter than the lifespan of the individual affected," they conclude. "Evolution occurs similarly in Armillaria individuals, but over a span of centuries and millennia, and is characterized by extreme genomic stability. The genomic stability of Armillaria and the underlying mechanisms allowing such stability may provide a useful counterpoint to cancer."

The study not been peer reviewed, so its findings and conclusions have not been rigorously assessed by other scientists. It can be accessed here.