I'm David Hibbett, professor of mycology.

I'm here to answer your questions from Twitter.

This is Mushroom Support.

[upbeat music]

Okay, first up from nicolesimoneau3 who says,

Why do mushrooms have to look like that?

I'm trying to enjoy them,

but their physique makes me uncomfortable.

A mushroom has one function and that is to liberate spores.

The shapes of mushrooms that have evolved

through natural selection have been optimized

for spore dispersal.

So a spore is a cell that's designed to be disseminated,

to be distributed by wind

or water or insects or some other means.

A bracket fungus, like this,

might produce a billion spores a day.

A giant puff ball can produce literally trillions of spores

and an awful lot of mushrooms

have a shape like this, with a cap and a stalk,

maybe gills underneath,

maybe pores, maybe teeth, and that tells us that,

this must be the right shape for a mushroom.

This must work really well for spore dispersal.

Most spores don't make it.

They don't end up germinating and forming a new fungus,

but the fungus makes many, many spores

in order to maximize its chances

of reproducing successfully.

Shelia Crimmins asks,

What's the difference between Cremini,

Button, and Portobello Mushrooms?

Well, the difference is really just a matter of age,

because all of these types of commercial mushrooms

are the same species, Agaricus bisporus.

They're all the same thing.

They're just harvested at different stages of the lifecycle.

The classic little, white Button mushroom

with the closed cap is harvested very early in its life,

before the cap has started to open,

before the spores are mature.

So the gills are gonna be just a pale pink

and not particularly flavorful.

Cremini mushrooms are harvested a little bit later on,

they've started to turn brown, developed some pigmentation.

The cap has started to open,

started to turn brown as the spores have matured.

And the Portobellos are the fully mature Agaricus bisporus,

the cap has opened up, it become kind of flattened out.

The veils that conceal the gills as they develop,

have broken away, and the gills

have that beautiful, dark brown chocolate color

and they've also started to develop a lot more flavor.

Fabrice Senger asks,

A carnivorous mushroom, how scary is that?

So first of all, yes, there are carnivorous mushrooms.

In fact, this innocent looking fungus,

the Oyster mushroom, is a carnivore.

It's also a wood decay fungus.

This naturally grows in nature on tree trunks,

but this fungus also is able to trap, kill,

and consume tiny worm-like animals, called nematodes.

And it does this at the level of the mycelium.

This fungus produces tiny little protuberances

off the sides of the hyphae, microscopic little projections,

from which it secretes a droplet of fluid

and that fluid contains a potent neurotoxin.

When the nematode, this tiny little worm-like animal,

comes in contact with that neurotoxin,

it's esophagus, it's throat basically,

you can see it contort

and then the fungus grows into that nematode

and digests it from the inside out.

Fuzzysemi asks,

Why did mushrooms evolve to have psychedelic properties?

You shouldn't assume that magic mushrooms evolved

to have hallucinogenic properties for the benefit of humans.

In fact, magic mushrooms probably don't care

about humans at all.

Lots of fungi and plants for that matter,

produce chemicals whose primary function

is to deter grazers.

In the case of psilocybin mushrooms,

I've heard an idea suggested recently,

that psilocybin may actually interfere

with the digestion of slugs.

Slugs are major grazers on mushrooms.

So if that is true, then it is just a happy accident

of evolution that we can get high

feeding on what is essentially slug poison.

Okay, now we have something from the FUNBIT_project.

How do mushrooms defend themselves?

Defend themselves against what?

I mean, the way that mushrooms defend themselves

from animals that would like to eat them,

is by producing chemicals called secondary metabolites

that effectively act as poisons.

Fungi also need to defend themselves against other fungi.

You can see this in a culture in the laboratory on agar.

You can also see it if you take a slice through a log

that's been colonized by multiple species of fungi,

and you'll see these dark black interaction lines.

That's what spalted wood is,

which is very highly prized by wood workers,

because the fungi, in the process of fighting over turf,

make beautiful patterns

from the interaction zone lines in wood.

The next question comes from FemdomFarm.

Do you happen to know if there are any major differences

between mushrooms that grow on wood [dead or living]

versus mushrooms that grow from the ground?

So if a mushroom is growing out of a log,

it's a pretty good bet

that that's a wood decay fungus, right?

If a mushroom is growing out of the ground,

it might also be decaying dead organic matter

that's in the soil, like buried roots or wood or something.

But it could also be mycorrhizal.

So mycorrhizal fungi grow in partnership with trees.

The fungi deliver mineral nutrients to the trees,

and in return, the trees provide sugars,

which they make through photosynthesis, to the fungus.

Ellamking asks, How do zombie ants become zombies?

I'm gonna push back on this question just a little bit,

because I think it's a misuse of the word zombie.

Zombie ant fungi do not reanimate ant corpses.

They're what we call necrotrophs.

They're fungi that can infect, kill,

and then eat another organism,

an ant, in the case of the zombie ant fungi.

But when the zombie ants are dead,

they are truly dead and they are not coming back.

Rhcm123 asks,

Could a parasitic fungus evolve to control humans?

If you're asking, could Cordyceps or one of its relatives

make the jump from an insect to a human

and control us and kill us,

I'm not terribly worried about that myself,

because our biology is so wildly different

from that of arthropods, like insects and so on.

Now, it's true that the group of fungi

that include the zombie ant fungi,

have made lots of host jumps,

but most of those are host jumps to other kinds of insects,

like onto cicadas or grasshoppers

or moth larva or something like that.

There are other fungi that I am worried about, however.

There's something called Candida auris, which is a yeast,

related to the yeast that we make beer and wine from,

and this is an emerging pathogen, that is drug resistant,

that crops up in lots of hospital settings

and it's a very serious concern.

But I'm not afraid of Cordyceps.

Im_tired_yall says,

Do any of you grow mushrooms at home? How?

With a cultivation kit? Is it worth it?

Any tips/advice/recommendations?

It's tremendous fun growing mushrooms.

It's kind of miraculous to watch them emerge

from a block of sawdust.

If you buy one of the commercial kits,

they make it very easy, because what you get

is a fully colonized block of substrate,

which is usually based on sawdust,

and you just have to set it up and the mushrooms will come.

The challenge is providing the right environment

for the mushrooms.

And the big challenge there is humidity.

Mushrooms like about 90 to 95% humidity

in order to fruit optimally.

Luke Greensmith asks, Fungus is never not nightmare fuel.

Why is it neither plant nor animal?

Let's just take a step back and point out

that not all of life is plants or animals.

That's a really old idea.

Fungi are on this branch of the tree of life,

called the Opisthokonts,

which also contains animals, plants are very far away,

in a group that's called the Archaeplastida,

that also includes algae and so on.

Plants also obviously have chloroplasts.

They can do photosynthesis

and that's something that both fungi and animals cannot do.

So this plants versus animals dichotomy

is something that is very old

and that we're still working hard to try to overcome.

Next question is from Hank Green.

Sometimes I think it would be nice

to be able to focus on a single thing,

but other times, I think what's the biggest mushroom?

There are some really big mushrooms out there,

but the largest mushrooms are wood decaying fungi

that grow on massive substrates, like trunks of trees.

So for example,

here's a wood decay fungus called Ganoderma applanatum.

It's also called the artist's conk

and it grows on tree trunks and it gets quite big.

Here's another similar one.

This is called Phellinus tremulae, or the Aspen bracket.

So these are pretty big,

but these are nowhere near a fruiting body

of a mushroom called Phellinus ellipsoideus.

That's 35 feet long, and it was discovered

on an island in China, on Hainan Island,

and it can get that big because it's feeding on

a very massive, persistent woody substrate,

that it can eat and fruit from over many years.

Pseudonym Jones says, I really like veiled lady mushrooms

because they're pretty and also alien looking,

but mainly because scientists are like, cool, right?

No idea why it does that.

The veiled lady mushroom goes by a number of names,

sometimes it's called the Veiled Stink Horn,

the Bridal Veil mushroom, the Bamboo mushroom.

The scientific name is Phallus indusiatus.

So the species name, indusiatus,

refers to a skirt or a tunic

and these fungi make a beautiful lace-like, veil-like

structure that hangs down from the fruiting body.

We have a pretty good idea for why it looks the way it does

and that is to attract insects.

Most mushrooms release their spores into the air

and they drift off on the wind

and hopefully land somewhere where they're gonna germinate,

grow, find a good habitat,

and eventually make more mushrooms.

Stink Horns exploit insects to disperse their spores.

The veil of that Veiled Lady must be a visual attractant

for spore dispersing insects.

And then on the head of the fruiting body,

the fungus produces a brown, slimy fluid

called the gleba that contains the spores,

and which smells like feces or decaying meat.

It's pretty repulsive,

but if you're a fly or a carrion beetle or something,

you'll find it very attractive.

Lou talks about nature asks,

Spooky. What's the weirdest mushroom in your opinion?

For my money, the spookiest mushroom

is something that's called Hydnellum peckii,

and the common name for this is the Bleeding Tooth.

What really makes this thing interesting

is that it exudes droplets of fluid

on the top of the fruiting body that are bright red.

So this is a tooth mushroom

that looks like it is dripping, oozing blood.

Bear Dooro says,

How can you tell if a mushroom is poisonous or not?

Well, sorry, Bear Dooro,

but there is no simple, foolproof universal test

to tell whether or not a fungus is poisonous or not.

You just have to know what you're dealing with

and it's really hard to learn how to identify mushrooms

from say, a book or from websites.

The best way to learn how to ID mushrooms

is to connect with somebody who's good at mushroom ID

and get them to take you out in the woods

and teach you a few edible mushrooms.

Okay, we have one now from my_real_name who says,

Mushrooms have 50,000 sexes. How many genders?

Most mushrooms, like the ones in front of me here,

have two different mating genes.

And in order for mushrooms to be mating compatible,

they have to have different variants of those genes.

We call those alleles.

So the number of sexes, so to speak,

is determined by the number of variant alleles

of each of those mating genes.

The most famous mushroom

in which this process has been studied

is something called the Common Splitgill,

or Schizophyllum commune.

This fungus can produce 28,000 unique sexes.

So fungi are non-binary in the extreme,

and the concept of gender

has absolutely no applicability in fungi at all.

Grace_hall313 says,

How am I supposed to believe my biology teacher

when she tells me that humans and mushrooms

are closely related?

Well, first of all, everybody knows that biology teachers

are among the most honest

and trustworthy people on the planet

and in this case, she's right.

So humans and mushrooms and other fungi and other animals

are all in a branch of the tree of life

that's called the Opisthokonts.

So when your biology teacher tells you

that mushrooms and humans are more closely related

to each other than either is to plants,

she's got it absolutely right.

So you should believe everything she says from now on.

Maoacdh13 who says,

What part of the mushroom are the spores?

I'm so disgusted.

Well, first of all,

I don't know why you find spores disgusting.

I find them beautiful, especially under the microscope.

The spores are produced on the underside

of the mushroom fruiting body, on the gills or in pores.

Individually, you can't see them.

They're microscopic, but in mass you can see them.

So sometimes mycologists make what's called a spore print,

where you turn a mushroom upside down

and put it on a piece of paper,

and then you can see the color of the spores

when they're deposited in huge numbers.

Now we have something from sassygayroot who says,

What is the mycelium and what does it do?

You can think of it as like the vegetative body

of the fungus, and it's really quite a miraculous structure.

It's composed of millions of tiny, microscopic

thread-like filaments that mycologists hyphae,

and they radiate out into the substrate

that the fungus is growing through.

The substrate could be soil, wood,

a loaf of bread in your kitchen, your toenail.

This is the part of the fungus

that explores its environment,

captures territory, captures resources,

fights with other fungi, and mates.

So the mycelium is really quite an amazing

and important phase in the life cycle of a fungus.

RSocPublishing, which is Royal Society Publishing, asks,

Can mushrooms talk to each other?

It depends on what you mean by talk.

So obviously mushrooms do not vocalize,

but they do communicate in some way

and they communicate biochemically.

So when mushrooms bump into each other,

when the mycelia of two different mushrooms interact,

they have to figure out who they're dealing with.

Maybe they're bumping into another member

of their own species with whom they might like to mate

or they're bumping into a different species

and they're gonna fight with that other individual.

And so they're going to exchange biochemical signals

and recognize self, non-self,

mating incompatible, not mating incompatible.

I don't know if you consider that talking,

but they certainly do exchange information biochemically

to determine who they're dealing with.

Pneumacia says, There are bioluminescent mushrooms?!

Yes, there are bioluminescent mushrooms

and they're totally cool.

We have come to understand a lot

about the biochemistry of how they produce that light.

It's an enzymatic reaction that does it.

A more mysterious question is why they do it.

It could just be a metabolic byproduct.

It could have no function at all.

But there have been at least a couple of studies

that have suggested that in some cases,

that light might actually help to attract insects

that might carry off the spores.

Legalizeshroom1 has two questions.

Why am I in this tyrannical police state called the US?

And, Why do magic mushrooms grow on cow poop?

So I cannot help you with the first question,

but for the second one, I will say,

that there are lots of fungi that grow on animal dung.

We call those Coprophilous fungi.

So dung loving fungi.

Dung turns out to be

a really nutritious substrate for a fungus.

It's got lots of nitrogen compounds,

it's got sugars, it's got carbohydrates.

It's the great place to be a Coprophilous fungus.

Rosie Boyd asks, Why do mushrooms grow in circles?

That shit is so cute!

We call that a fairy ring.

And in the olden days,

people thought that fairy rings represented places

where the fairies or the elves had been dancing

and people were nervous

to step into the middle of a fairy circle.

Now, we know that the reason that mushrooms

often fruit in a circle like that,

is because of the structure of the mycelium.

So the mycelium, that network of filaments

that makes up the vegetative body of the fungus,

all other things being equal,

in a uniform environment will grow out in a circle

and that's how you get a fairy ring.

That's how you get that circular arrangement of mushrooms.

Breadjamin201,

How many species of mushrooms are there?

You know, we've been studying fungi for centuries

and you would think that by now

we would know how many species of fungi

there are on the planet, but we don't.

So most of the mushroom forming fungi

are in a group that's called the Agaricomycetes

and there's about 30 or 35,000 described species

of Agaricomycetes.

But if you look at all of the fungi together,

including molds, yeasts, mildews, plant pathogens and so on,

there's about 145,000 described species.

The number of species that actually exists on earth

is certainly much, much larger.

Some people think that there might even be

as many as 165 million species of fungi on the planet.

So what that means is that if you're interested in mycology,

it's a great field to make lots of new discoveries.

And for me, that's very exciting.

Todd G Baker asks, Mowed my grass yesterday evening.

This morning this lone mushroom had appeared.

How can anything grow so fast?

The answer is that some mushrooms can grow very rapidly

by absorbing water and inflating their cells.

Probably when he mowed his lawn,

the primordia, the little structures

that are gonna give rise to the fungus,

were already there waiting for the right conditions

to absorb water and push up a mushroom.

So now we have something from Learning with Ms. A, who says,

Our science wondering question today,

how do mushrooms decompose organic matter?

Can they decompose inorganic matter?

When you say organic matter,

I assume that you're talking about

something like wood, leaf litter, something like that.

Fungi decompose that kind of organic matter

by growing into it with their hyphae,

those filaments that make up the mycelium,

and they release digestive enzymes

into the material they're going through,

digest the organic matter around it,

and then absorb the small molecules

that are the breakdown products of that digestion.

And that's not terribly different from what we do,

except that we digest our food inside our bodies,

whereas fungi digest their food

outside their filaments with these secreted enzymes.

To a scientist, organic compounds

are just carbon-based compounds, including a lot of things

that you might not think of as organic, including coal, oil,

various petroleum products, like plastics,

and also some pesticides, polycyclic aromatic hydrocarbons,

which can be very nasty pollutants in the environment.

And some fungi, in particular, White-Rot fungi,

which are a kind of fungi that decay wood,

have been shown to be able to break down

those kinds of organo-pollutants, at least in the lab.

And that's driven a lot of interest

in what's called myco-remediation,

the possibility that we could use fungi in the environment

to clean up some of the messes that humans have left behind.

SushiFox0 says,

Why is everyone obsessed with mushrooms all of a sudden?

Is there something I'm missing?

Everybody should be obsessed with mushrooms.

Mushrooms are incredibly beautiful, incredibly diverse.

They play critical roles in the ecosystem.

Some of them are delicious, some of them are deadly,

some of them are hallucinogenic.

And another great reason to be interested in mushrooms

is because of the people.

The huge community of amateur mycologists

and community scientists who get together

and form mushroom clubs

and go out and do forays and grow mushrooms

and they're eager to share what they know.

You should join a local mushroom club

and there are dozens of them all over North America

and then you too can become obsessed with fungi.

Okay, that's all the questions.

Hope you learned something.

Thank you for watching.

Until next time.