I discovered this neat little fungus growing on some beaver-downed logs at the research station earlier this week. It was unusual in that it was fuzzy, and it caught my eye because of the attractive lobing of the growths into neat leafy shapes. I went back once the sun was high enough to peek over the trees and took a few photos.
Unfortunately, the field guide I had used to identify the fungi back in January had been a library book, so I didn’t have it on hand. And trying to find the identity of something is much aided by a field guide like that. There aren’t any good, complete references online (or at least, if there is one I didn’t stumble across it in my searching). However, I finally discovered something that closely resembled my fungi while browsing search results from ForestryImages.org.
Sure enough, further investigation reveals it to be Schizophyllum commune, or the split gill fungus. The genus name literally means “split leaf”. And naturally, the key identifying feature of this fungus, the split gills, I had no photo of. I had peeked under the cap to check out whether it was gilled or pored, determined that it was gilled, and left it at that. Who knew it was that important?
I actually do have an image of the split gills, above. This is a crop-down from one of the larger photos, which just happened to have one individual curling up enough to expose its underside to the camera, which was nearly overhead. It actually looks more like paired gills, rather than split, with the ridges radiating in twos out from the centre. Schizophyllum is the only genus with this characteristic, and is in fact so unique it has its own family, Schizophyllaceae.
There’s a handful of species in this genus, but Schizophyllum commune is by far the most common. It’s found across North America, and in fact occurs on every continent except Antarctica, where there’s no wood for it to grow on. It superficially resembles the commonly-found bracket fungi that grow on trunks and logs, but has these “gills” instead of pores. The gills aren’t actually spore producing the way they are in true gilled mushrooms, but are instead simply folds of tissue.
Similar to the Mycena corticola I posted about in January, these fungi are marcescent: they can dry out over the winter months or during periods of low moisture, and then come back to life at the next rains. This adaptation is part of what makes this fungus so successful around the world. Rather than growing new fruiting bodies each year, the fungus’ “roots” (the mycelium) only have to produce one growth which will last throughout the year, even during dry spells.
Fungus reproduction is a complex thing, where compatibility of external mating structures is less important than compatibility of genomes. In order to reduce the likelihood of inbreeding, a fungus can only “mate” with other fungi that have a different DNA sequence (allele) at a gene location (locus) from their own. To compare to humans, it’s like blue-eyed people only being able to mate with brown-, green-, or hazel-eyed people, but not other blue-eyed people. In fungi, there’s usually two loci used in mating compatibility, and each locus has multiple alleles. In the case of Schizophyllum commune, there’s more than 300 alleles at the first locus, and over 90 at the second – resulting in more than 28,000 allele combinations. So instead of the two sexes found in vertebrates (male and female), there’s 28,000 sexes in this species of fungus! This enormous number means any given individual will be compatible with over 99% of the rest of the population (vertebrates are only compatible with 50%).
One other wild thing about this fungus – it doesn’t just stick to rotten logs. There have been a number of reports (though very rare) of the spores of this fungus (presumably inhaled) infecting the respiratory tract of humans. For instance, this poor woman had the fungus actually growing in her sinus cavity! Of course, it probably didn’t have these lovely fan shapes inside her nose, and it was identified using DNA sequencing. In another, the fungus had grown through the soft palate of a child and was forming fruiting bodies in her sinus. I can’t find the actual paper on that one to determine whether they were actual mushroom-shapes, though all the sites that mention it sure make it sound that way (this site is where I read it first). Others document lung, airway, and even brain infections.
So be careful not to inhale too deeply when you bend over to check this neat little fungus out…