It's a Bird! It's a Plane! No, It's Pyrenomyxa picea! – A Yearslong Mystery Solved

 

February 6, 2016

I'll set the stage: It's almost eight years ago. I'm in the woods with the dog, slogging through deep snow, looking for whatever I can find. Winter is actually a great time to discover all kinds of obscure stuff you might otherwise miss in the summer and fall when it's easy to be distracted by all the flashy fleshy fungi that proliferate in those warmer months. 

Ontario winter with Ruby

I see it from a distance on the bare trunk of a standing dead aspen, a vibrant rust-coloured stain that contrasts sharply with the near monochrome of the winter woods. I see, too, an Armillaria's black mycelial cords knotted around the pale trunk like macramé – remnants of the mushroom that was almost certainly responsible for the tree's death.

Bright rust-red stains

Almost there (it's slow going) and I can see that there are elongated dark and gnarly lumps attached to the reddish stains. 

At this point, I'm pretty sure I've been hoodwinked into making a beeline for a string of raccoon or fisher turds that are somehow stuck to the side of the tree; I have been tricked by poop before.

What the hey?

But then I'm right there and, since the lumps are conveniently located at torso level, I can inspect them closely. The rust-red stain is not only on the tree, it has also given the lumps a gorgeous rust-red patina in the crevices of their otherwise polished black exteriors. The lumps also seem devoid of hairs, or insect shells, or berries. Altogether, a bit weird for scat. 

I'm now thinking along the lines of Hypoxylon or Daldinia, hard carbon fungi that have pigments. Or maybe even something related to Camarops petersii, the Dog's Nose Fungus.

Daldinia childiae can sometimes be really lumpy.

Camarops petersii (Dog's Nose Fungus) is also pulvinate in form.

I need to touch one. I don't poke it – just in case I'm wrong about it not being scat – I just gently touch it. It immediately collapses, its shell cracking, my fingertip coming away with a dusting of black spores. Definitely not poop, then. But what the heck is it?

Its hard shell is easily shattered.

The only thing I know of that would behave like this is one of the larger Myxomycetes, or slime moulds, that form aethalia – sessile, pulvinate lumps packed with not much other than hundreds of thousands of spores. Possibly something along the line of Reticularia. Reticularia splendens, and R. lycoperdon, (the False Puffball), both have similarities to my lumps, though their spore masses are brown, not black. 

Reticularia splendens is shiny and dark.

Its larger sister, Reticularia lycoperdon, can sometimes look
as if it's been dipped in aluminum paint. Its outer coating is,
however, always extremely thin and tears rather than cracks.

So maybe some kind of Fuligo, though not Fuligo septica, Dog's Vomit Slime, which is always crusty and never smooth and shiny, but maybe something akin to one of its more defined siblings, like F. leviderma.

The outer crust (peridium) of the slime mould, Fuligo
leviderma, is very thin and easily broken...

 

...and its spores are black. Unlike the mushroom I
found, though, the black spore mass inside Fuligo
is shot with light coloured pseudocapillitium. 

Nothing, though, really fits what I've found, and the pigment, both the staining of the wood and the patina on the cortex is throwing me off. The only thing I can do is take some home but it's impossible to collect an intact sample. This thing is crazy friable and fragile; the tree is not decayed enough to cut into the wood and when I try to slide my knife under a section of one of the lumps to pry it off the tree, its shell shatters into multiple shards and its insides mostly crumble to dust. So that's what I take home with me.

 

Slime Mould or Fungus?

 

Basically, I don't have a clue what this thing is. I don't even know what kingdom it belongs to. Fortunately, though, I have a microscope so I will likely be able to rule out one of two kingdoms fairly quickly: If the spores aren't round, my find is not a slime mould.   

 

And they aren't. Instead, they're dark little finger bananas (or, technically, phaseoliform, elliptic-inequilateral) with a slit down their backs. So my first thought was right – my mushroom is likely to be one of the pyrenomycetous Xylariaceae fungi, like Hypoxylon and Daldinia.  

The dark brown phaseoliform, or bean-shaped, spores.

But there's a problem with this diagnosis. All of the members of this group of flask fungi that I know of release their spores through ostioles – openings in the surface of their sporocarps. Even under magnification, I can't see any of these openings. So how does this mushroom release its spores? 

The spores of Daldinia childiae are released through its pimply
perithecial mouths (ostioles) creating a polka-dotted spore print.

Though textured, the outer surface of my find is devoid of ostioles.  

It seems to me that perhaps the spores are meant to be released passively after the outer shell breaks down, the same way the slime moulds mentioned above do. There does seem to be some kind of fibrous structure near the base, but it is in such bad shape it's impossible to tell what the structure might have been before it collapsed. 

I spend the next couple of days going through my books and searching on line for clues as to what my fungus is, but I get nowhere. I'm stumped. So I post it on Facebook's Ascomycetes of the World group, begging for an ID. I get no answers. I dry my specimen and file it away.

Fast Forward a Couple of Years

 Somewhere, I see a photograph of Camillea tinctor. I get all excited because a) like my mushroom, C. tinctor is black and b) it clearly stains the wood beneath its sporocarp a bright rust-orange. Could this be my mushroom?

Camillea tinctor is a hard carbon fungus that stains the
wood beneath it a bright rust-red. (courtesy Tom Bigelow)

Close, but no cigar. Though the wood staining is impressive, C. tinctor is fairly flat, very hard and has papillate ostioles. Sigh. It's also not found anywhere near where I live in southeastern Ontario. It is, however, common in the New York City area, though it was not reported there until 2016 when Ethan Crenson noticed its proclivity to wood dyeing, which its better-known sister, C. punctulata (which has puctate ostioles) cannot do. The farthest north it has been found since then is just south of Albany, New York. If you find this mushroom, please post it to iNaturalist so that its range can be tracked!

 

Fast Forward to Two Weeks Ago: Serendipidy

 So then the most fun thing happens. I'm rummaging through my Facebook groups and suddenly, there it is, my mushroom! At first I even think I'm looking at my photographs, but no, it's someone else's find, David Chapados's. His look just like mine. I immediately post a picture of my seven-year-old observation. David has already suggested Hypoxylon. There is discussion and other guesses from the experts: Camarops, Daldinia, and yes, maybe a slime mould such as Reticularia. None of these make sense to David any more than they made sense to me almost eight years earlier. Still no one is coming up wih a name. What a buzzkill. 

David Chapados's observation from Quebec.

But here's the serendipidy part: Six days later, someone – a mushroom angel – spurred on by the mystery, pokes and prods iNaturalist until she finds the answer. After starting her search with “Xylariaceae,” which gets 38,000 North American hits, or a few too many to wade through, she tries paring it down to "Pyrenomycetes" which, in its full form, frustratingly links back to the more general “Higher Ascomycetes” with about half a million useless hits. But below that she sees something that catches her interest: a genus called Pyrenomyxa. Knowing that David and others think the mushroom has similarities to slime moulds, or “myxos” as some of us call them, she clicks on the single species and – ta da! – there’s Garrett Taylor’s observation of Pyrenomyxa picea. Clearly the same mushroom. And we have a name! Thank you, Hélène Lafond!

The Name's the Thing

Naturally, this gets me doing the mushroom name dance. Names can sometimes be incredibly hard to find, especially if you're an amateur, so a bit of celebration should be expected. When I've stopped dancing, I start reading about my mushroom on line.

Of course Pyrenomyxa picea isn't its first name. It's a big enough entity that J. B. Ellis found and described it 135 years ago, naming it Hypoxylon piceum (didn't we all say Hypoxylon at some point?). Then, in 1977, it turned into Pulveria porrecta (Malloch & Rogerson, 1977). And now, with a very distinct nod to this weirdo's resemblence to some of the slime molds (Myxomycetes), it has perhaps been given its final name, Pyrenomyxa picea (Stadler, Læssøe, & Vasilyeva, 2005) – the picea/piceum part of its epithet obviously based on it eventually turning "pitch black," (which, for those born more recently than me, means "black as tar"), and not having any relationship at all to spruce trees since it's known only from angiosperms.

It's definitely an oddball. Its habit is to form under the bark of dead trees, (the bark on my tree had recently fallen off) so actively ejecting its spores out of its asci would be a waste of time and energy so it has no apical spores or plugs at all. Also, peculiarly, these cleistothecial* asci are produced along "ascogenous hyphae" (see illustration below). I particularly love the way the 8 spores in each almost spherical ascus are nested together like the segments of a clementine. 

The crazy reproductive elements of Pyrenomyxa
picea from the Malloch & Rogerson paper.

Yellow-green KOH-extractable pigment

David Chapados's beautiful cross-section

The only thing missing is that there are no mentions in the descriptions of this mushroom about the striking rust-red colouration of the surrounding wood and the crevices of the sporocarps that is so dominant in my observation, David Chapados's observation, and also in my friend Garrett Taylor's 4-year-old observation on iNaturalist. 

Maybe David Malloch, who co-wrote the 1977 paper, will have some insight. He replies to my email query immediately and says that though he had actually followed the growth of his P. picea over several months, its sporocarps, though reddish-brown when they first appeared, had no such colour later on. So that part remains a mystery. 

Malloch also says that even though it's "kind of a monster fungus once it starts developing," it seems uncommon. I spend a couple of days on iNaturalist trying to determine how uncommon it is by scouring through several thousand images of Daldinia, Hypoxylon, Kretzschmaria, and Reticularia to see if I can find any over-looked observations in northeastern North America. And I do! Not a lot – but a couple that are unmistakably this mushroom. These and a couple of other possible ones make it clear that this is a) not common and, b) a late season organism: all of the observations were made in October or November.  

As I write this, it just so happens to be late season. So this is a good time to go hunting for this special mushroom. Look for standing dead hardwood trees (poplar, ash, maple) with loose bark. For a full description, Mycoquebec has already made a page for it with one of David Chapados's photogaphs. If you do find it, please post it on iNaturalist or Mushroom Observer!

*cleistothecial - from cleistothecium, a globose, completely enclosed fruit body with no special opening to the outside. Like truffles.

References

Malloch, David W and Clark T. Rogerson. “Pulveria, a new genus of Xylariaceae (Ascomycetes).” Canadian Journal of Botany 55 (1977): 1505-1509.

Stadler M, Laessøe T, Vasilyeva L. The genus Pyrenomyxa and its affinities to othercleistocarpous Hypoxyloideae as inferred from morphological and chemicaltraits. Mycologia. 2005 Sep-Oct;97(5):1129-39.

 New Brunswick Museum's Xylariomycetidae Page

Garrett Taylor's iNaturalist Pyrenomyxa picea observation

Mycoquebec's Pyrenomyx picea page

My iNaturalist Pyrenomyxa picea observation where I have copied links to other observations I am either sure are the same mushroom or ones that I think might be.