Many of the mold (<i>Armillaria gallica</i>) is underground, but in the autumn sprouts honey mushrooms.
A giant fungus lurking underground in Michigan is extremely old, extremely heavy and has a very low mutation rate, a new study found.
Here are the fungus’ impressive stats: It is at least 2500 years old (although it is probably much older), it weighs almost 882,000 lbs. (400,000 kilograms) and covers about 75 hectares (0.75 square kilometers, or 140 American football fields). The mutation rate or the rate at which random genetic changes occur, it is volatile low, said study co-principal investigator, Johann Bruhn, professor emeritus of plant sciences at the University of Missouri.
“We think that this slow mutation rate is perhaps the key to the genetic stability of the giant fungus, and possibly even an important reason for the great durability,” Bruhn told Live Science. [Microscopic Worlds Gallery: pictures of the Fascinating Fungi]
Bruhn came for the first time on the other side of the absolute unit (Armillaria gallica) in the late 1980’s, when he was working on a non-related experiment in the woods of Michigan in the Upper Peninsula. He roped in two fungal experts, James Anderson, now at the University of Toronto, and Myron Smith, now at Carleton University in Ottawa, Canada, who also co-principal investigators on the new study. The large mold blew the researchers, who at first greatly underestimated his size and age. (When she thought it was a fungus about 1,500 years old, 220,000 lbs. (100,000 kg) and approximately 37 acres (0.3 km), according to their 1992 study published in the journal Nature.)
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At the time, the audience went bonkers about the large fungus, which is also known as honey, mushrooms, Bruhn recalled. Late night comedian David Letterman made a “Top 10” list about Johnny Carson cracked jokes; and a New York City restaurant even called to see if it could purchase the mold to serve on the dinner menu.
Bruhn fell to the restaurant of the request, but noted that well-cooked honey mushrooms are edible, although eating too much can give you stomach ache. “They must be well-cooked, and they should not be eaten in excess,” he said. “But I have enjoyed them on home made pizzas.”
The second look
Now, almost 30 years later, is the scientific latest experiments reveal the true greatness of the A. gallica, Bruhn said. Despite its size, the fungus is largely under the ground, out of sight. The fungus makes use of a part of the energy that it obtains from the rotting wooded foodbase to grow branches branches known as rhizomorphs, which are located by the bottom of the forest, looking for their next meal. Rhizomorphs attach themselves to the roots of the trees. Once the tree is vulnerable, for example as a result of drought or pests or fire, the fungus attacks, sapping the tree of nutrients and decaying wood in a white rot. Every autumn the fungus sprouting mushrooms, allowing the fungus to reproduce.
From 2015 to 2017, the scientists again, the giant fungus, and took 245 samples, so that she could be a whole genome sequences of the genetic material. They estimate the age of 2,500 years by analysing the fungus’ growth. However, this particular A. gallica could be even older, because there are other Armillaria species in the area, which may be hindered, A. gallica ‘ s growth, Bruhn said.
It is a mystery why A. gallica has a low mutation rate, but it would be a biological mechanism, the researchers said. Or, perhaps it is the fact that it is largely under the ground, away from the mutation-causing ultraviolet rays of the sun, may explain the low rate of mutations, Bruhn said.
During the study shows that the Michigan A. gallica is indeed a giant, it is not the largest mold that are out there. “Indeed, at least two other individuals a brother or sister Armillaria species (A. solidipes) were reported to occupy larger areas in Washington and Oregon, the researchers wrote in the study.
The study today is published online (Dec. 19) in the journal Proceedings of the Royal Society B.
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Originally published on Live Science.