Emu Dung Fungus

There is a genus of puffball fungus called Pisolithus which includes a number of closely related species. In Europe it is gastronomically known as the Bohemian truffle, and in the US it is prosaically called the dyemaker's puffball. But in call-it-like-it-is Australia it is known colloquially as the horse dung fungus – because that’s pretty much what it looks like. In the central Australian Pitjantjatjara language it’s apparently called ayinkura, but I don’t know if or what that might translate to.

This is a pile of horse dung. It is not a group of puffballs (stock photo)

Pisolithus is a type of puffball or earth ball fungus, from the family Sclerodermataceae. The name Pisolithus means “pea-stone” (pisum is Latin for pea, and lithos is Greek for stone). It is not a kind name to those afflicted with a lisp, and is rather difficult to say more than a few times in quick succession (though I can’t see any reason why you might want to do so!).

There are a number of species of Pisolithus around the world, and it appears there are several in Australia, with some only being recently discovered / described. And I’m not certain which species I’m dealing with in this post, but it may be Pisolithus arrhizus, or Pisolithus albus, or Pisolithus marmoratus, or Pisolithus tinctorius, or some similar species…

There is another type of fungus called ‘horse dung fungus’ but it is a very different type of fungus and it gets the name because it grows in horse dung rather than looking like horse dung. It is the common inky cap mushroom Coprinopsis cinerea, and it looks instead like a fairly typical small pixie-capped type of mushroom. But it has recently been in the limelight because it produces a novel antibiotic compound with much potential in the fight against the growing prevalence of antibiotic resistant bacteria as a result of the overuse of antibiotics (see for example http://www.natureworldnews.com/articles/10189/20141110/horse-dung-fungus-bizarre-help-vs-antibiotic-resistance.htm).

But I digress.

On a recent bird-banding trip to the Weddin Mountains in central NSW, we came across a dried out emu turd. It was fairly weathered, starting to crumble, and exposing a mass of barely digested seeds.

Old, dried and weathered emu dropping at Weddin Mountain National Park, NSW.

Other emu dung I have seen, in the wet mountain ranges near Canberra, have been wetter, greener and distinctly peaked from cloacal constrictive forces. 

Fresh, soft and moist emu droppings at Tidbinbilla Nature Reserve, ACT.

So there can be some variability in the appearance of emu dung, and I figure I can be excused for initially mistaking a large round Pisolithus for another emu dropping when I first rushed past it.

But it was sufficiently different for me to do a double-take and when I turned back for a closer look, realised it was a firm immature fungus with a rather spotted golden brown surface. 

Large, firm, immature Pisolithus puffball fungus at Weddin Mountain National Park, NSW.

I whipped out my baby Swiss army knife and sliced it cleanly in half (or nearly so) and was amazed by the incredible structure and pattern that was revealed.

The inside of an immature Pisolithus puffball presents an unexpected display of colour and pattern.

The pea-sized spore bundles or locuoles supposedly resemble peas!

The pattern results from the variable stages of development of the spore bundles, or locuoles - it is the appearance of these locuoles that prompted the name “pea-stone”.

It was pleasing to find that when we next returned to Weddin Mountains a month or so later, the half of the puffball that was still rooted (hyphaed?) to the ground had continued to grow and the cut surface had healed over – so it still had its chance to puff its spores into the wind when it ripened.

The scarred-over cut surface and continued growth of this Pisolithus puffball made me feel less guilty about having inflicted the damage on it in the first place.

And just to round out this post, below is a photo of another small clump of Pisolithus that I came across at the wetlands in West Wyalong, showing the more typical appearance that elicited the horse dung fungus appellation.

A small cluster of Pisolithus puffballs starting to resemble horse dung.

But to me, these things will now always be emu dung fungus.

Some references:

https://en.wikipedia.org/wiki/Pisolithus_arrhizus

https://en.wiktionary.org/wiki/ayinku%E1%B9%9Fa

http://blogs.scientificamerican.com/artful-amoeba/wonderful-things-the-hidden-beauty-of-the-horse-dung-fungus/