How big can a living organism be

The second largest known organism on the planet is much larger than expected

It is not entirely clear where its German name comes from. Probably, however, the honey mushroom has something to do with the buttocks: One doctrine says that the honey mushroom helps against hemorrhoids (hence "Heil im Arsch"), another that the mushroom, which can even be fatal when eaten raw, causes diarrhea ( hal = smooth, again in A ....).

The fungus does not only cause discomfort in humans: it is a parasite of many deciduous and coniferous trees and can cause great damage in forestry and orchards. Only the yellowish fruiting bodies are visible; underground the actual fungus grows like mycelium between the bark and the wooden part and spreads from tree to tree and over roots through meter-long strands as thick as a shoe.

Quadrupling the mass

At the end of the 1980s, researchers working with James Anderson (University of Toronto) discovered a honey-yellow honey fungus (Armillaria mellea) in the US state of Michigan, which was then declared the largest known creature on the planet: According to calculations at the time, the monster mushroom spread over around 37 hectares (1 hectare is about the size of a large soccer field) and weighed an estimated 100 tons.

Now the same team of scientists has visited the mushroom giant again to find out whether it is still alive. In fact, in the new analyzes, the researchers found not only that the underground giant is fresh and alive, but that it is still growing. And it should have about four times as much mass as originally thought: namely around 400 tons. That is twice as heavy as the largest blue whale.

Growth and mutation rate

To find out how big the huge underground fungal network actually is, the researchers took 245 fungal samples from far away and analyzed their genes. Many of them belonged to the same individual, as the researchers report in a study published on the bioRxiv preprint server. In addition, based on the growth of the underground strands, they were able to estimate how old the fungus is: namely at least 2,500 years old.

In addition, the minimal DNA changes between the samples allowed conclusions to be drawn about the rate of mutation: Apparently the genome of the monster mushroom changes extremely slowly. Reasons for this could either be sophisticated DNA repair mechanisms and / or simply the fact that the subterranean plexuses are not exposed to UV radiation that causes mutations.

And that is the largest living being

Now you are probably wondering what the (at least in terms of area) largest known creature on the planet is. That might be the representative of another honey fungus species called Armillaria ostoyae. This fungus was discovered in 1998 in the Malheur National Forest (Oregon, USA) due to an initially puzzling forest dieback.

The gigantic mycelium of this dark honey fungus extends over almost ten square kilometers, more precisely: 965 hectares. That is roughly as large as the area of ​​the 1st, 6th, 7th, 8th and 9th districts of Vienna combined. The age of this mega-mushroom should be a proud 8,000 years. (tasch, October 20, 2018)