top of page

The Brown Roll-Rim (Paxillus involutus)


Paxillus involutus

Good evening, friends,


Well, no snow covered mushroom this week. Instead we’re dipping into the fall archive to look at the the Brown Roll-Rim (Paxillus involutus). This non-descript little mushroom was poking out from the base of a dead hemlock stump when I knelt down to look for a different mushroom, the Rosy Conk (Rhodofomes cajanderi). I didn’t recognize this mushroom, but I did notice reddish brown bruising when I started to handle it which made me think it could be identified. I shared my finding on the New York Mycological Society’s zoom ID session and, boom, they were able to help me identify this potentially dangerous mushroom.


I also have significant news. As to not bury the lede: I have activated donations/pledges on Substack. For over three years, I’ve written weekly out of pure fascination and appreciation for mushrooms and ecological education. I’m taking this new step in accepting voluntary (not required) payments to see if this can be more than a personal passion, but also a way of life. I’ll detail the whole process at the end.


Notice the scurfy margin of the cap (the cottony bits at the edge of the cap).
Notice the scurfy margin of the cap (the cottony bits at the edge of the cap).

Fun Facts


Consumption of this mushroom can result in “fatal immunohaemolysis”, also known as Paxillus Syndrome, which is when one’s antibodies attack their own red blood cells. Fascinatingly, this mushroom is consumed regularly in certain parts of the world - one of them Kazakhstan - but there are only a handful of documented fatal poisonings.

Reference 2 documents two separate incidences, both in Kazakhstan, where a 46-year old and a 32-year old died of Paxillus Syndrome. Both had previously eaten the mushroom multiple times without any incident, but both also had preexisting conditions (one a genetic condition and the other Hepatitis C) that made them susceptible to hemolysis - the breakdown of red blood cells. The ill-effects started just a few hours after consumption and both died in great discomfort in the hospital a few days later (believe it or not, when your red blood cells deteriorate it does not feel good). If you want more detail you can read the paper.


Some mushroom compounds bioaccumulate in the body and have beneficial, adaptogenic effects while others bioaccumulate in the body and make your white blood cells attack your red blood cells. Unfortunately, it’s still unknown which specific compound(s) in P. involutus causes this fatal reaction in some individuals.


In latin, you may know that Pax means “peace”, but Paxillus means “peg” or “pin”. I’m not entirely sure how that relates to the fungus outside of the idea that the mushroom is like a peg sticking out of the ground? The species epithet, involutus, refers to the in-rolled (involuted) margin of the cap (seen above). The edge of the cap tucks back under itself instead of fleshing out straight.
In latin, you may know that Pax means “peace”, but Paxillus means “peg” or “pin”. I’m not entirely sure how that relates to the fungus outside of the idea that the mushroom is like a peg sticking out of the ground? The species epithet, involutus, refers to the in-rolled (involuted) margin of the cap (seen above). The edge of the cap tucks back under itself instead of fleshing out straight.

In latin, you may know that Pax means “peace”, but Paxillus means “peg” or “pin”. I’m not entirely sure how that relates to the fungus outside of the idea that the mushroom is like a peg sticking out of the ground? The species epithet, involutus, refers to the in-rolled (involuted) margin of the cap (seen above). The edge of the cap tucks back under itself instead of fleshing out straight.


Can you see the mushrooms? They don’t necessarily pop out on the forest floor.
Can you see the mushrooms? They don’t necessarily pop out on the forest floor.

Ecology


Interestingly, the fungus is allegedly both saprobic (a decomposer) and mycorrhizal (a symbiont) with both hardwood and conifer trees. These specific mushrooms were found growing from dead conifer which makes me speculate that the fungus (in this instance) is saprobic, but some mycorrhizal mushrooms can also appear on dead wood. It should also be noted that mycorrhizal fungi are saprobes until they find a partner.


The appearance of this mushroom is also variable as the cap can range in color from brown to yellow to a fleshy pink. The mushroom typically has a funnel shape, but that wasn’t the case with our specimen. The only thing that seems to be certain is the more we learn about this mushroom, the less we know.


I took a nibble from the cap, let it sit on the front of my tongue, and spit it out. The mushroom smelled and tasted chemically, citrusy, and fresh. There was also bruising at the point of nibbling.
I took a nibble from the cap, let it sit on the front of my tongue, and spit it out. The mushroom smelled and tasted chemically, citrusy, and fresh. There was also bruising at the point of nibbling.

The fungus is distributed broadly across North America and temperate regions of the northern hemisphere. The mushrooms have also been found in South America, Africa, and Australia - so they’re on every continent outside of Antarctica. The mushroom has a lot of look-a-likes, and probably falls under the category of LBMs (Little Brown Mushrooms), but look for the bruising and the distinct smell to start.


I guess we do get a snow (or ice) capped mushroom after all.
I guess we do get a snow (or ice) capped mushroom after all.

Mushroom Monday a Sellout?


Folks, I’ve decided to start accepting pledges. After nearly forty months of writing Mushroom Monday (and the occasional Toadstool Tuesday) for the pure love of mushrooms and ecology, I’ve gone corporate and will now accept your money. I’m not a great businessman, and talking/thinking about your money makes me uncomfortable, so this was no easy decision. I do spend several hours researching and writing each week and, truthfully, I want to see if this can be more than a weekly email but also a livelihood (or at least a portion of one). That being said, I set all the pledges as low as Substack would allow.


The local paper up here has an economic model that I admire and would like to emulate. The Highlands Current is free for anyone to read, but if you enjoy the work you can elect to become a member and support them with an annual fee. Membership gives you added content and benefits.


I really like this paper.
I really like this paper.

Mushroom Monday will always be free every week. I will still do free mushroom walks in Central Park and Connecticut too. But if you want to support this work and become a member, the initial added benefit will include a bi-weekly newsletter on a different ecological topic. The first publication (early Feb) will be on beavers and how they survive the winter. In the summer, I’m going to do weekend trips where I look for specific flora, fauna, and funga that I’ll write about for members as well. Maybe we’ll make t-shirts, maybe we’ll get some videos going, who knows. Like a mushroom, we’re going to absorb a lot of water and grow.


Thanks for reading and here’s to many more years of learning,

Aubrey


References:

  1. Kuo, M. (2008, February). Paxillus involutus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/paxillus_involutus.html

  2. Stöver A, Haberl B, Helmreich C, Müller W, Musshoff F, Fels H, Graw M, Groth O. Fatal Immunohaemolysis after the Consumption of the Poison Pax Mushroom: A Focus on the Diagnosis of the Paxillus Syndrome with the Aid of Two Case Reports. Diagnostics (Basel). 2019 Sep 26;9(4):130. doi: 10.3390/diagnostics9040130. PMID: 31561486; PMCID: PMC6963215.

bottom of page