Fungus Fact Friday

Tagged: taxonomy

how fungi are related to one another and other organisms

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Fungus Fact

#011: Characteristics of Fungi

What is a fungus?  That question has been answered many ways over the years, reflecting an evolving understanding of this strange group of organisms.  Initially, fungi were classified as a class in kingdom Plantae.  As our understanding of the chemistry, life history, and evolution of fungi improved, Fungi was elevated to the rank of kingdom.  Kingdom Fungi is placed in domain Eukarya and belongs to the major clade Opisthokonta.  Opisthokonta also includes the kingdom Animalia, which makes animals close relatives of the fungi.  But going beyond taxonomic definitions, what makes a fungus a fungus?  It’s hard to answer that question because the fungal kingdom is very diverse and there are many similar organisms in other kingdoms.  As a simple answer, Fungi are heterotrophic filamentous (or unicellular) eukaryotes with a chitin cell wall that reproduce by spores and digest their food externally.

arbuscules in root 2

Fungus Fact

#015: Characteristics of Division Glomeromycota

The Glomeromycota are unusual and poorly understood organisms. Fungi from this division rarely produce easily visible structures and cannot be grown without a plant host, so investigating them is very difficult. Glomeromycotan fungi are some of the most important fungi on Earth because they form arbuscular mycorrhizas, which provide essential nutrients to the vast majority of terrestrial plants.

Mycena leaiana 4

Fungus Fact

#027: Gilled Mushrooms (Agarics)

The gilled mushrooms, informally referred to as ‘agarics,’ are the type of mushroom with which we are most familiar. The most common edible mushrooms (white/button/portabella mushrooms, oyster mushrooms, and shiitake mushrooms), Amanita muscaria – the most recognizable mushroom in the world and the inspiration for almost all mushroom art – and the ‘magic mushrooms’ are all gilled mushrooms. All these mushrooms share one feature: vertical plates of spore-producing tissue stacked under a sterile cap.

Hypomyces chrysospermus 2

Fungus Fact

#158: Hypomyces chrysospermus, the Bolete Eater

Occasionally, you encounter something that has the stature and shape of a bolete but is completely smooth underneath its cap. “What can this be?” you ask. “No crust fungi are this fleshy or have such a well-defined cap and stem.” It turns out that you did find a bolete, only it is being parasitized by another fungus! Hypomyces chrysospermus is a common parasite of all kinds of boletes. It forms a crust that often completely engulfs its host. The “Bolete Eater,” “Bolete Mold,” or “Golden Hypomyces” is easy to identify, thanks to its preference for boletes and its white to yellow color scheme.

#048: Mushroom Morphology: Jelly Fungi 0

Fungus Fact

#048: Mushroom Morphology: Jelly Fungi

As you might guess, jelly fungi are distinguished by their gelatinous consistency. Their external appearance varies widely, so their texture is the only macroscopic feature that defines this group.  These fungi are placed within the phylum Basidiomycota, but they produce basidia (spore-bearing structures) unlike those of most other basidiomycetes (for more on basidia see FFF#013).  Because of this, they are often placed in the artificial group of fungi called heterobasidiomycetes.  The heterobasidiomycetes also include rusts and smuts, which do not form mushrooms.  Jelly fungi produce three different variations on the normal basidium (holobasidium) morphology.  Holobasidia have a bulbous, undivided base topped with spore-bearing steritmata.  The first variaition on this model is the cruciate basidium.  Cruciate basidia have a bulbous base divided into four cells by septa (cell walls).  The septa are at right angles to one another, making a cross shape when the basidium is viewed from above.  A good...

#047: Mushroom Morphology: Truffles 1

Fungus Fact

#047: Mushroom Morphology: Truffles

Truffles are ascomycetes that form below-ground (hypogeous) fruiting bodies. These mushrooms look like small, lumpy potatoes on the outside.  When cut open, truffles have a marbled appearance.  Like the false truffles and sequestrate basidiomycetes, true truffles have evolved to retain moisture in arid climates or other harsh conditions.  Truffles evolved from cup-shaped ascomycetes with a spore surface exposed to the air.  To keep the spores moist, the cup became closed.  Eventually, the interior surface became wrinkled and condensed, creating the marbled interior.  There are a number of truffle species that exhibit various stages along this evolutionary path.  Many of these truffles are hollow on the inside, as the gleba (interior, spore-producing tissue) has not fully become compacted.  All truffles rely on animals – usually small mammals – to dig up the fruiting bodies and eat them.  Truffles attract these animals by producing various scents.  These scents are what give edible...

#044: Mushroom Morphology: Earthstars 1

Fungus Fact

#044: Mushroom Morphology: Earthstars

In celebration of Independence Day, I will be discussing the festively-shaped earthstars. Earthstars are characterized by a puffball-like sphere surrounded by a star-shaped base.  The earthstars all have a three-layered peridium (the surface that covers the developing spore tissue).  At maturity, the two outer layers split into rays and peel back to form the star-shaped base.  The endoperidium (interior layer) then develops an ostiole (pore) ringed by a peristome through which spores are discharged.  Earthstars are included in the gastromycetes, which all form their spores internally and cannot forcibly discharge their spores.  Instead, like the puffballs, spores of earthstars are forced out of the pore when raindrops land on the endoperidium.  All earthstars have capillatum, a network of cells designed to help spores move to the pore when a raindrop strikes the mushroom.  If you cut open an earthstar you will find that it looks nothing like the interior of...

#043: Mushroom Morphology: Bird’s Nest Fungi 2

Fungus Fact

#043: Mushroom Morphology: Bird’s Nest Fungi

These small (< 1.5cm) fungi are easily recognizable by their striking resemblance to a bird’s nest with eggs inside. The “eggs” are actually spore-containing sacks called peridioles.  As in the other gasteromycetes, the bird’s nest fungi produce spores internally and have lost the ability to forcibly discharge their spores.  To overcome this obstacle, the bird’s nest fungi developed their unique morphology to act as a splash cup.  The basic splash cup mechanism works as follows: a raindrop falls into the cup, which propels one of the peridioles (“eggs”) out of the cup.  The next challenge for the bird’s nest fungi is to stick to whatever they land on.  These fungi have evolved two different mechanisms in order to accomplish this.  Fungi in the genera Mycocalia, Nidula, and Nidularia have peridioles that are covered in sticky mucilage, which allows them to adhere to surfaces on contact.  Fungi in the genera Crucibulum...

#042: Mushroom Morphology: Earthballs 2

Fungus Fact

#042: Mushroom Morphology: Earthballs

This group of mushrooms goes by a variety of common names, including “earthballs,” “earth balls,” and “false puffballs.” Additionally, all of these mushrooms belong to the family Sclerodermataceae and could casually be referred to as “sclerodermas.”*  Using these terms to distinguish earthballs from puffballs is a fairly recent development, so many earthballs are still commonly called puffballs.  Visually, immature earth balls can look similar to puffballs.  If you are collecting puffballs to eat, make sure you know how to tell the difference between true puffballs and the usually poisonous earthballs.  The main difference between earthballs and puffballs is that, unlike the puffballs, earthballs do not release their spores through a regular pore.  Instead, the peridium (outer layer) cracks and tears irregularly.  Like all gasteromycetes (fungi whose spores mature internally), earthballs have lost the ability to forcibly discharge their spores.  The spores mature in the center of the earthball, enclosed by...

#041: Mushroom Morphology: Puffballs 5

Fungus Fact

#041: Mushroom Morphology: Puffballs

The puffball is probably the second most familiar mushroom morphology. Many people can remember finding one of these as a child and giving in to the uncontrollable desire to kick the ball-shaped mushroom.  Anyone who has tried this knows that your efforts are rewarded with a fabulous puff of spores.  This puff is not just for the amusement of small children but is actually a rather ingenious spore dispersal mechanism.  Puffballs are gasteroid fungi, meaning that spores develop inside the mushroom.  All gasteroid fungi have lost the ability to forcibly discharge their spores, so they have to come up with other ways to release their spores.  Puffballs achieve this by puffing their spores out of small openings.  When the spores are mature a small opening (or a few small openings) called an ostiole develops on the surface of the mushroom.  When a raindrop (or an animal’s/ someone’s foot) lands on...