Mushroom Monday
Brown-Toothed Crust Fungus (Hydnoporia olivacea)
Good evening, friends,
Today’s mushroom I found just this morning: the Brown-Toothed Crust Fungus (Hydnoporia olivacea). Now that all the leaves have fallen off the trees (besides marcescent leaves), one’s mushroom eyes turn from looking down at the earth and soil to looking more at logs and limbs. Like the false-turkey tail from a couple weeks ago, this is another crust fungus that is quite common in the northeast and persists throughout the year. You can go outside and find this mushroom right now, and when you do there’s one specific feature you’ll want to see.
Fun Facts
Hydnoporia is a genus of crust fungus, formerly known as Hydnochaete, that can actually “glue” branches and limbs together. The crust can spread from one branch to another, where the branches are touching, and then act as a natural bind. Kind of interesting that the fruiting body, the mushroom, can grow on and attach two different substrates when the fungus is theoretically only living inside of one substrate? Or perhaps through the sustained physical contact of the branches, the fungus can inhabit both?
The fertile surface of a basidiomycete fungus (the vast majority of mushrooms you’ll see during your day to day) is made up of basidia and cystidia. On a crust fungus like we’re looking at today, basically the whole mushroom is the fertile surface (where spores are released). Conversely, the top of the cap of a portabella mushroom wouldn’t be considered fertile surface because the spores aren’t released from the top of the cap.
Basidia cells produce the spores, the reproductive cells. Cystidia cells are larger, and can be used to help identify mushrooms, but their function in the mushroom itself isn’t fully understood. Some mushrooms use them for excretory purposes to discharge liquid, but what and why they’re releasing that liquid isn’t even truly understood.
Cystidia are usually looked at under a microscope since they’re a singular cell, but the cystidia on H. olivacea are large enough to see with ~nearly~ the naked eye. I used the macro-camera, but you can also use just a hand lens. If you consume enough Vitamin A and squint hard enough then you might not even need a hand lens. I think it’s possible.
In this instance, the cystidia are long and dark-colored which classifies them as setae. Like rectangles and squares, all setae are cystidia but not all cystidia are setae. This extra classification adds another vocab word to the mix and an extra layer of confusion to confound us further. Regardless, setae - those dark hairs in the pictures - are the key identifying characteristic you want to see in this mushroom.
Ecology
The fungus is saprobic and decomposes dead hardwood. Interestingly, a study found this fungus occupying the sapwood (the living, active wood cells in a tree) of a conifer found in Southeast Asia (Reference 3). I’ve only seen it on hardwood but if you’re in Southeast Asia check your softwoods too. The individual teeth are only millimeters long, but the entirety of the fruiting body can spread over dozens of centimeters.
The fungus fruits in the traditional growing season, late spring through fall, but the durable crust can be found year-round. The range is a little peculiar - per iNaturalist, the fungus only seems to grow in eastern North America, but then there is that study of the fungus’s existence in Asia. More research is needed. Regardless, if you do happen to be in eastern North America you can walk out your door and find this mushroom any time of the year - I found three different fruitings just today.
Have a great holiday season and we’ll talk again on the other side of the winter solstice. I’ve got a book report and more of a journalistic piece planned, but those will be released right around the start of the new year. Then we’re back to regularly scheduled emails in January and more winter mushrooms.
Enjoy the crisp air and look for winter fungi until then,
Aubrey
References:
Zhang HB, Yang MX, Tu R, Gao L, Zhao ZW. Fungal communities in decaying sapwood and heartwood of a conifer Keteleeria evelyniana. Curr Microbiol. 2008 Apr;56(4):358-62. doi: 10.1007/s00284-007-9092-6. Epub 2008 Jan 9. PMID: 18183460.
https://www.mushroomthejournal.com/greatlakesdata/Terms/seta132.html
https://www.inaturalist.org/taxa/1038656-Hydnoporia-olivacea
"The crust can spread from one branch to another, where the branches are touching, and then act as a natural bind. Kind of interesting that the fruiting body, the mushroom, can grow on and attach two different substrates when the fungus is theoretically only living inside of one substrate? Or perhaps through the sustained physical contact of the branches, the fungus can inhabit both?"
That would be super cool to find out, it would make sense if it could live in both branches at once.