Chapter 18: Phylum Basidiomycota: Gasteromycetes—The Puffballs, Earthstars, Stinkhorns, and Bird's Nest Fungi

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When we think fungi,

you know, our minds usually jump straight to the classic mushroom shape, right?

The kind you put on a pizza.

Right, the standard cap and stem.

Exactly.

But what if I told you there's this whole other world of fungi out there, under our feet, sometimes right out in the open, that look?

Oh.

Just bizarre.

Oh, absolutely.

Forms you wouldn't even recognize as fungi at first glance.

We're talking things that look like tiny bird's nests or puff balls that literally puff smoke, or even some that smell.

Famously bad to attract insects.

You're setting the scene perfectly.

It's a really diverse group.

Welcome to the deep dive.

Today we're jumping into the honestly fascinating world of the gastromyces.

The stomach fungi, literally.

Right, and we're using a key chapter from introductory mycology as our guide.

So our mission today, to explore this really varied group within the Basidia mycota, we'll look at their unique structures, their incredible ways of reproducing and getting spores out there.

Their ecological roles, which are super important.

And crucially, how scientists are rethinking where they fit in the fungal family tree.

Because the big thing, the defining trait, is that their spores mature inside the fruiting body.

Yep, and they are not forcibly shot out, unlike many other mushrooms.

That's the key.

So stick with us and you'll get a real shortcut to understanding these hidden wonders.

Expect some surprises, maybe a few aha moments about fungi that are way more dynamic than they look.

It's fascinating how that one single thing maturing spores inside completely changed their game plan, evolutionarily speaking.

Now so.

Well, unlike your average gilled mushroom that just, you know, shoots spores into the wind, these gastromyces had to invent totally different ways to disperse.

Some are pretty spectacular, actually.

It's like a whole series of natural experiments and getting offspring out.

Pfft.

Pfft.

Pfft.

Pfft.

Pfft.

Pfft.

Pfft.

Completely different from a gilled mushroom where spores are just dropping constantly, carried off by air currents.

And you see this even though they look so different on the outside, right?

You mentioned puffballs.

Puffballs, earth stars,

the very fragrant stinkhorns and those charming little bird's nest fungi, they look nothing alike sometimes.

But internally.

Internally they share that core strategy, spores made on the inside.

Okay, let's talk structure.

They all have this outer layer, the peridium.

What is that exactly?

The peridium is basically the skin, the outer wall, but it's incredibly varied.

Sometimes it's paper thin, other times thick and tough, almost rubbery, and it can have layers one, two, or even three distinct layers, exo, endo, sometimes a mesoperidium in between.

So it's not just a simple covering.

Not at all.

And how it opens, or if it opens, is key to releasing the spores.

It might split, form a little pore, or in some species it just breaks down over time.

It's their protective shell, but it's also part of the dispersal plan.

Got it.

A strategic shell.

And inside that shell is the glaba.

Exactly.

The glaba is the fertile bit inside, packed with the spore -producing tissue.

Think of it like the spore factory floor.

And the texture inside can vary, too.

Some are just made of thin -walled hyphae.

Others have these thick -walled supportive structures called capillitium mixed in.

Capillitium.

Yeah, they're like internal scaffolding.

They give the glaba structure.

And they're actually really important for telling different species apart.

Mycologists look closely at those.

So internal details matter for identification.

What about the actual cells making the spores, the basidia, and the spores themselves, the basidiospores, are they different, too?

They all have these single -celled hollow basidia.

That's pretty standard.

But the spores, the basidiospores, sometimes called status myspores, are positioned symmetrically on their little stalks, the sterigmata.

Symmetrically, why does that matter?

Because it means they aren't built for being shut off.

They just detach, fall off when mature.

No forceful ejection.

Ah, okay, so they don't launch, they drop.

Precisely, and that simple difference dictates everything about how they get around.

Many also produce loads of spores, often more than the standard four per basidium, and the spores themselves are often thick -walled, packed with lipids, probably helps them survive the journey.

Which brings us to how they do get around.

Since they don't shoot spores, how do they disperse?

You called it a remarkable series of experiments.

It really is.

For the ones growing above ground, the apidus ones, it can be pretty straightforward.

Wind, rain, just the fruiting body weathering away.

Like a puffball drying out and the wind carrying the dust away.

Exactly.

Simple but effective for many.

But then you get the stinkhorns.

Yeah.

They're definitely not simple.

Oh, the stinkhorns.

Yeah, species like dictyphora or phallus, their strategy is, well, pungent.

Understatement.

They produce this incredibly strong, fedded, odor -thick rotting meat.

It's full of chemicals like hydrogen sulfide, methyl mercaptan.

Designed to attract flies.

Exactly.

Flies are drawn in, land on the sticky, spore -filled gleba.

The spores glom onto their bodies, their mouth parts.

And get this, the spores can often survive passing right through the fly's digestive system.

No way.

Yep.

So the fly lands somewhere else, does its business, and boom, dispersed spores, ready to go.

It's brilliantly effective, if a bit gross.

And that smell and their distinctive shape have certainly gotten them noticed by humans over the years, right?

Didn't Darwin's daughter have a thing about them?

Oh, the famous story about Eddie Darwin.

Yes, apparently she used to hunt down phallus imputicus, the common stinkhorn, because its shape was considered, well, indecent.

Unashamedly phallic, I think, is the term.

Right, and she'd burn them, supposedly to protect the morals of the local young women.

It just shows how these unusual fungi have always caught our eye, often for slightly scandalous reasons.

A great anecdote, but okay, that's above ground.

What about the ones under the ground, the hypogeous ones?

Right, the underground crew, like false truffles.

If they're buried, how on earth do spores get out?

That seems like a huge challenge.

Animal helpers are key here.

These fungi often produce specific smells to attract certain animals, mammals, sometimes invertebrates.

Smells, like the stinkhorns.

Sometimes, but not always bad smells.

Some, like protubera, are described as smelling fruity, like passion fruit or apples.

Quite appealing, actually.

So animals dig them up and eat them.

Exactly.

They munch on the basidiocarps, break them open, and the spores get spread around.

Sometimes animals even carry them back to their burrows first.

And I bet those spores are tough, too.

Incredibly tough.

Just like with the fly dispersal, spores from many of these hypogeous gastromyces, and true truffles, too, can survive the trip through a mammal's digestive system.

So they germinate from, well, from droppings.

Precisely.

It's a really effective way to disperse and start a new life cycle, perfectly integrated into the ecosystem.

These dispersal tricks are just amazing.

But let's talk impact.

What do these fungi actually do out there, ecologically,

economically?

Well, ecologically, most are either sap robes, breaking down dead stuff, recycling nutrients, super important.

The cleanup crew.

Kinda, yeah.

Or they're mycorrhizal forming those essential partnerships with plant roots, helping plants get nutrients and water.

Mostly on land, I assume.

Mostly.

But there are weird exceptions.

Remember Neovabrissa?

That's a marine gastromycid, a woodrotter.

It actually got famous from munching on the wood of Henry VIII's warship, the Mary Rose, after it was salvaged.

Wow, fungi making Tudor history.

That's wild.

But you mentioned mycorrhizal ones.

Isn't there one that's really important for forestry?

Yes, you're thinking of Pissolithis tincturius.

Absolutely crucial.

What makes it so special?

It's an amazing ectomycorrhizal partner, especially for pines, but other trees too.

It's used commercially in a big way for reforestation and reclaiming land.

How does it help?

It helps trees survive and grow in really tough conditions.

Hot soil, poor nutrients, acidic soils, like on old strip mines.

It gives them a massive advantage.

So people actually use it.

Oh yeah.

There was pioneering work done by D .H.

Marks at the USDA Forest Service,

developing ways to inoculate seedlings with P.

Tincturius before planting them out.

Huge success.

Won awards for it.

It's a real workhorse fungus for restoration.

That's a massive impact.

What about eating them?

Any good edibles in this group?

Definitely.

Puffballs are the main ones.

Things like Calvasia cyphiformis, or the giant puffball, Calvasia gigante.

That's giant, are we talking?

Seriously giant.

They can get over 70, maybe 80 centimeters across, like beach balls.

And one of those monsters can produce something like, wait for it, seven trillion spores.

Seven trillion.

I can't even comprehend that number.

It's astronomical.

But yeah, edible when they're young and pure white inside.

Crucial safety point though.

Always slice a puffball top to bottom before even thinking about eating it.

Why is that?

To make sure it's not actually the egg stage of a different possibly poisonous mushroom, like an Amanita.

The inside of a true puffball should be uniform,

undifferentiated tissue when young.

An Amanita egg will show the silhouette of a tiny mushroom inside.

Very important check.

Good tip.

Always be sure.

And didn't you mention a stinkhorn being eaten somewhere, despite the smell?

Yes, surprisingly.

Dictyophyr duplicata, the one with the lacy skirt, is commercially grown and eaten in parts of Asia, usually in its egg stage before the smell develops, I believe.

And historically, those dusty spores from puffballs were apparently used to start bleeding.

Kind of a folk remedy.

Fascinating uses.

Okay, let's dive into the different types now.

The structural variety is huge, starting with Lycopridales puffballs and earth stars.

Right, so in the Lycopridaceae family, you have your classic puffballs.

Calvaceae species often just have a thin outer wall, the peridium, that flakes away.

And Lycopriden.

Lycopriden is the one where the outer layers often wear off, leaving a tougher inner layer with a definite hole at the top, the osteal.

The puffer.

Exactly, you tap it or rain hits it and puff go the spores out the osteal, hence the name.

Makes sense.

And the earth stars, geez, Tracy, they look amazing.

They really do, they have three peridial layers.

When it gets wet, those outer layers split and peel back into star -like rays, it's beautiful.

Like geostrum.

Yep, geostrum is the classic example.

This exposes the inner spore sac.

And amazingly, they actually found a fossil geostrum recently, which is super rare for fungi because they usually decay so fast.

A fossil fungus.

Cool.

Okay, next up.

Tulostoma tails,

stocked puff balls.

Yeah, these typically grow above ground, but some start underground.

That Hypotesia star might help them survive dry spells.

Then they send up the stalk, sometimes really tall, like in Bataria over 30 centimeters.

Why so tall?

Lifts the spore sac way up high.

Yeah.

Better chance for wind dispersal.

Clever.

Then Scleroderma tails, earth balls, false earth stars.

They sound tough.

They often are.

Scleroderma, the earth balls, have this really thick, tough peridium.

It doesn't usually form a neat osseal.

It just splits irregularly when mature, revealing this dark, powdery spore mass inside.

And you mentioned they can explode.

Well, I've heard stories from herbarium curators.

If you collect one that's still closed and it dries out completely on the shelf, poof!

Spore cloud everywhere when it finally bursts.

Must be quite a cleanup.

I bet.

And the false earth stars?

Estreus.

They look a bit like geostrum with the star rays, but their rays show this amazing hygroscopic movement.

They open up when it's wet,

exposing the spore sac, but clamp down tight when it's dry.

Like a little moisture -sensitive door.

Exactly.

Protects the spores until conditions are good for release.

And Pissolithis tincturius, our reforestation friend, is also in this order.

Structurally, it's interesting because its young glaba has these distinct little packages of spores called peridials, like peas in a pod, almost.

Okay, let's go back to the phallales, the stinkhorns.

You said they start as an egg.

Yeah, this whitish sort of gelatinous egg stage looks innocent enough.

You could mistake it for a puffball or maybe an Amanita egg if you weren't careful.

Inside, though, the whole stinkhorn structure, the receptacle has already formed, just compressed.

Waiting to emerge.

Exactly.

And when it's ready, the internal pressure builds, ruptures the egg shell, the peridium, which stays at the base as a vulva, and the receptacle expands incredibly fast, sometimes in just a few hours.

And carries the smelly glaba up with it.

Right.

Once it's exposed to air, the glaba starts to autodigest, breaks down into that slimy, green, foul -smelling goo that the flies just love.

It's quite the performance.

It really is, and the shapes vary so much.

From the simple column of phallus to dictyophora with that amazing lacy skirt nendusium to clathrospecies that look like intricate hollow lattices, incredible forms.

Truly bizarre and beautiful.

Uh -huh.

Okay, one more group.

Nidularialis, bird's nest fungi, and the cannonball fungus.

These are delightful.

The bird's nest fungi look just like tiny nests or cups.

And the eggs inside.

Those are the peridials, little lens -shaped packages containing the spores.

How do they get out?

Raindrops.

It's called splash cup dispersal.

A raindrop hits the cup at just the right angle.

And flings the eggs out.

Exactly, ejects the peridials, and in general, like sciathus and crucivulum, it's even more clever.

Each peridial is attached by this tiny cord, the funiculus.

Yeah, cord.

Yeah, and it has this sticky end called the hapturon.

When the peridial gets splashed out, the force breaks part of the funiculus, the sticky hapturon flies out, hits a twig or a leaf, and sticks.

Like a tiny grappling hook.

Pretty much.

The peridial then swings around and wraps the cord around whenever it hit.

Amazing precision.

That is brilliant.

And the cannonball fungus, ferroblus.

Does it splash too?

Oh no, ferroblus is all about power.

It violently ejects a single sticky gleeble mass, the cannonball.

You can actually hear a little ping sometimes when it goes off.

Seriously, how far can it shoot it?

The record is apparently 569 centimeters.

That's almost 19 feet.

For a tiny fungus, that's incredible ballistic power.

Unbelievable.

What a tour of weird and wonderful fungi.

But now, the plot twist.

You mentioned our understanding of their classification is changing.

Right, this is where it gets really interesting for mycologists.

Based on all those shared features, especially internal spore maturation, they were grouped together for a long time.

But modern tools, especially RDNA sequencing, looking at their genetic code, have completely shaken things up.

It turns out the gastromycetes are what we call a polyphyletic assemblage.

That's a key concept.

It means they don't all share a single, unique common ancestor that defines the group.

They arrived at similar solutions independently.

Wow, so that internal spore thing, the stomach fungus idea, it evolved multiple times.

It's not a sign they're all one big happy family.

Exactly.

It's a case of convergent evolution.

Similar lifestyles or environmental pressures led to similar forms, but their deep evolutionary roots are often elsewhere.

So where do they belong?

Well, the molecular data shows that the closest relatives of many gastromycetes are actually outside this group.

For example, some of those odd sacotioid fungi, kind of like mushrooms that forgot how to open and many false truffles, turn out to be closely related to regular gilled mushrooms, agarics or boletes.

Really, like which ones?

A classic example is Rhizopogon, a common false truffle often found with pines.

Genetically, it's super close to soulus, which is a type of bolete mushroom that also associates with pines.

So a false truffle is basically just a bolete that decided to live underground and not shoot its spores.

In evolutionary terms, pretty much, it suggests that maybe only a few key gene changes, possibly driven by adapting to a dry or underground habitat, could lead to these massive changes in form and function relatively quickly.

That's mind blowing.

Evolution working fast.

It seems so.

There's even one wild case, gastroceulis laricinus.

Molecular evidence suggests it might have evolved from a normal soulus species, soulus pravillae, incredibly recently, maybe within the last 60 years or so, just a local mutation that became a gastromycete form.

60 years, that's an evolutionary eye blank.

It really is.

Now, these sacocioid forms, while they represent these interesting evolutionary shifts, often have a bit of a disadvantage.

They aren't good at air dispersal anymore, but they also might lack the really specialized animal dispersal strategies of the true hypogeous fungi, sort of caught in the middle.

So the big picture here is the term gastromycetes, while useful descriptively, is actually highly artificial from an evolutionary standpoint.

That's the modern understanding, yes.

Our view of fungal relationships is constantly being updated, refined by this molecular data.

It keeps things exciting.

Okay, let's try and wrap this up.

We've journeyed through the gastromycetes, the stomach fungi.

We saw incredible shapes, from puff balls to stinkhorns to bird's nests.

We looked at their ingenious ways of getting spores out there, wind, rain, flies,

mammals, even explosive cannons.

We touched on their vital ecological roles, decomposing and partnering with plants, and that amazing reforestation fungus, basalithus.

And maybe the biggest aha moment, realizing that this group, as traditionally defined, isn't really a natural group based on shared ancestry.

It's a collection of fungi that arrived at similar solutions independently.

Which really makes you think, doesn't it, about how we categorize life, how many other groups that seem obvious based on appearance might turn out to be, well, not what they seem, as our tools get better.

Absolutely, the fungal kingdom especially still holds so many secrets and surprises.

We're constantly learning.

It really drives home how much more there is to discover.

Well, thank you for joining us on this deep dive into the absolute wild world of gastromycetes.

We hope you stay curious.