5 Aug 2016

Who Knew What Grew on Poo?

pilobolus lentiger growing on dung
A large colony of Pilobolus, also called the
Hat Thrower or Dung Cannon 

I don’t want to offend anyone’s delicate sensibilities (or maybe I do!), but this post is about poo. More specifically, it’s about a secret world that grows on poo, a secret world than can be fascinating and sometimes—of all things!—strikingly beautiful.
cheilymenia stercorea growing on deer dung
This Eyelash Cup (Cheilymenia stercorea) grew on deer droppings.

I'm talking about coprophilous, or dung-loving, fungi. These fungi are our friends, as are all decomposers. They help dispose of what we don't want to see, breaking it down until it's nutritious compost—for the forest floor, the field, the garden. 

Some coprophiles are big. A few, like portobello and button mushrooms are good edibles (you did know that they're grown on a pasteurized substrate that contains manure, didn't you?). But most are so tiny you need a magnifying glass to see them. These are the guys I'm interested in.

ascomycetes growing on deer pellets
This deer pellet has three species growing on it. The tiny white
ones  grew into the smallest gilled mushrooms I've ever seen.

Right now, in fact, I'm trying to grow some of these mini characters on what used to be our dining-room table. 

About a week ago I was given a few samples of dried animal dung that are older than I am. At one time, these bits of dung had been studied, and then dried and stored, because interesting little fungi had been growing on them. The question is, are the spores that this dung holds still viable? Will fresh fungi appear? I have a bit of cow, goat, deer and rabbit dung, each now rehydrated and sitting in a moist chamber. Not much is happening yet, but I have high hopes.
Podospora fungus growing on rabbit pellet
The wee black cones at the top of this rabbit pellet are a kind of Podospora.

These samples I'm nursing originally grew either nondescript lumps called Sporormiella (a Latin genus that when spoken aloud makes you sound drunk) or cuter ones from the genus Podostroma. I found some Podostroma a couple of years ago on a rabbit pellet. Though it's not the prettiest fungus, it has very nifty black spores that sport see-through tails.

podospora spore
Podospora spore—with see-through tails at both ends!

The Royal Ontario Museum's fungarium has an immense collection of fungi, over half a million, a large proportion of which are dung-lovers, because one of the early directors of the collection, Roy F. Cain, was a world-renowned dung-loving fungi lover. But what's to love about about these lowly characters? 

Phycomyces hairy fungus growing on raccoon dropping
I found this amazing furry Phycomyces fungus on raccoon scat.
Well, besides some being pretty, many have adapted to their chosen dung homes in downright astonishing ways.

My favourite is Pilobolus, also known as the hat-thrower or cannon fungus. These sparkling jewels don't look very fungal. Each has a skinny stem that rises only a few millimetres above the cow patty or horse puck it grows on. At the top of the stem there's a bulbous, transparent, fluid-filled "head," a head that wears a black "hat." Clustered beneath the hat are its spores.

Pilobolus lentiger hat thrower fungus dung cannon
Close up of the Hat Thrower or Dung Cannon
So how do the spores of these fungi get into the dung in the first place? They're ingested by the animal. And no, horses and cows don't eat poo. In fact, they shun it just like you do. Pilobolus's brilliant solution to this problem is to blast their spores away from the poo they grow on—up to two metres away. Recent research has determined that their spore-carrying "hats" can reach a speed of 25 metres a second. But the most amazing part is the acceleration, which is the greatest of any living thing! Pretty impressive for something that's less than a millimetre in diameter.

Pilobolus spore capsule
Pilobolus head & spore capsule "hat" under the microscope
Pilobolus lentiger spores
When I squashed it under a slide cover, the spores were released.
Not only do these little guys shoot their spore capsules a distance away, they're capable of aiming with the help of a light sensor inside their stems. On top of that, they also have a sticky coating on the exterior of their black "hats" that makes them stick to nearby plants, where they cling at the perfect height to be eaten by a passing quarter horse or Holstein. 

Pilobolus lentiger on manure
The black dots are Pilobolus spore capsules or "hats" that stuck to
the wall of the plastic container I put the horse dung in. 

How can you not love dung-loving fungi when there are characters like this around?

If you'd like to read more about Pilobolus and other fascinating fungi, (including a couple of other dung-lovers—Eyelash Cups on Moose and Deer Droppings and A Poop and Scoop Cup Fungus), check out my fungi blog, Weird & Wonderful Wild Mushrooms.

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