Mushrooms are not only valued for their culinary properties but also offer a wide range of health-supporting benefits. To fully appreciate the power of these fascinating organisms, it is essential to understand their anatomy. Mushrooms come in various shapes, sizes, and colors, and while several species may appear similar, a close inspection of the cap, gills, or pores can reveal crucial details for accurate identification (1).
Fruiting Body
Fungi are multicellular organisms with an anatomy consisting of interconnected structures that produce spores, called basidia or asci. There are two main groups of fungi: microfungi, which live within other organisms, and macrofungi, which are visible to the naked eye and have fruiting bodies and root-like structures called mycelium.
Unlike plants and animals, fungi do not have a fixed body plan and instead develop through an evolutionary process that allows for frequent morphological transformations. Mushroom-forming fungi have been observed to have various morphological forms, including resupinate, pileate-sessile, coralloid, gasteroid, and complex stipitate. Despite these apparent variations, the basic developmental program is similar in most species and is controlled by several genes.
Fruiting body formation is a dynamic process that requires the coordination of multiple genetically encoded cell types and cellular structures. The complexity and evolution of mushroom-forming fungi’s morphology has intrigued mycologists for decades. Phylogenetic approaches suggest general trends in natural selection, but they lack the mechanistic details needed to understand evolutionary patterns. Until recently, most of the work on fruiting body development in mushroom-forming fungi has been conducted at the genetic level using lab models and naturally occurring mutants.
One distinguishing feature of mushroom anatomy is the presence of gills or pores. These structures are used by the fungus to release spores and form when mycelia become mature. There are many different types of gills, found in a wide variety of mushroom species. Anyone interested can also check out this guide to learn the parts of a mushroom.
Mushroom gills not only release spores but also protect them as they travel through the air. This is important because the spores are not very durable and could otherwise get damaged by other forces, such as wind or rain. The spores produced by gills are dispersed by air currents and transported to other locations where the fungus may grow. When the spores land in an environment with the right conditions, they germinate and produce new mycelia. As these mycelia continue to grow and mature, they will eventually produce more spores that can be dispersed by the same method.
Gills or Pores
The gills (or pores) under the mushroom cap are a key feature used to distinguish different species. These thin flaps resemble fish gills but don’t help the mushroom breathe; instead, they produce the spores used for reproduction. They are arranged in a fan shape under the cap to increase the surface area available for spore production and to allow for easy dispersal. Not all mushrooms have gills—some have no gills at all and instead have sponge-shaped pores.
Gills appear as a network of pores in the hymenium, a whitish or brown liquid that makes up the interior of a mushroom. The number and configuration of these pores is important for determining the identity of mushrooms. The distance between gills and the size of pores are also useful in identifying mushrooms, as is the color of the gills or whether they bruise a color distinct from that of the mushroom.
Most mushrooms with gills have a partial veil that covers the gills when they are young, but once the mushroom matures, this veil ruptures, exposing the gills to air and making it easier for the fungus to disperse its spores. However, some mushrooms have ridges that look like gills on the underside of their caps but are not actually gills. For example, the hymenium in chanterelles and pig’s ears mushrooms (Gomphus clavatus) forms forked ridges that have been described as resembling gills.
Another important characteristic to examine in a mushroom is how the gills attach to the stem. The gills can be attached directly to the stem, or they may diminish and then fork toward the stem, which is referred to as decurrent gill attachment. Other mushroom gills are narrow and only attached to the stem for a small portion of their length, known as emarginate gills. This gill attachment can be very distinctive in some mushroom species, such as the blewit (Clitocybe nuda). Some mushrooms, like portobellos or amanitas, have notched gills similar to emarginate gills but with unique features that set them apart.
Mycelium
Fungi play a critical role in breaking down organic matter, recycling waste materials, and nutrient cycling in the soil. They also provide a natural alternative to animal meat. It takes seven to nine weeks for a broiler chicken and a year and a half for a beef cow to grow enough meat for consumption, while mycelial networks can produce protein in just days.
As the fungus consumes and absorbs nutrients, it secretes enzymes that break down biological polymers into their component parts. The mycelium then transports these monomers into its cells by facilitated diffusion and active transport. The fungus’ mycelium is also responsible for forming the fruiting body and spores.
The mycelium is a unique feature that distinguishes fungi from plants and animals. It is a cellular network that allows fungi to grow and spread more efficiently than any other organism. Mycelium is also capable of forming complex structures like rhizomes and crusts, as well as the unique features that define mushrooms.
While most fungi reproduce asexually, some can produce spores to create new mycelia. These spores are produced when two compatible mycelial clumps fuse together. The resulting diploid spores can then form either a new mycelia or a fruiting body.
Spores can be blown in the wind or transported by other fungi to a new location. The spores are then able to develop into a new mycelium and begin the process of self-replication, called sporogenesis.
In a study on the morphological properties of mycelium, researchers found that it has a network-like microstructure with randomly oriented and sized filaments. It was also determined that the mycelium exhibits two types of fractal dimension: mass fractal dimension (DM) and surface (or border) fractal dimension, which is a subset of DM and only describes edges/borders of the mycelial system.
These characteristics allow the mycelium to respond to spatial nutrient variability in the environment by increasing or decreasing branching, allowing it to fill the available space. In addition, mycelial systems with high DM and low DS are more resilient to nutrient stress, whereas mycelia with lower DM and higher DS are more susceptible to nutrient stresses.
Spores
A fungus grows in a network of tiny hyphae that branch off in different directions to search for food. This is called sporulation, and it allows the fungus to spread its haploid genetic material far and wide. It also enables the fungus to adapt to its environment and disperse into new territory.
Spores are not as complex as their parent cells, but they must still possess a number of essential features to survive and grow. They must have a reserve of energy, a way to respond to environmental stress, and the ability to germinate and grow into a new mushroom.
To achieve these goals, the spore must be able to recognize specific nutrient signals that tell it to become metabolically active and germinate. This is accomplished by a protein in the spore cell that reacts with a special type of nutrient known as a germinant. The type of nutrient that functions as the germinant varies from species to species, but it is almost always a molecule that contains amino acids.
Once a spore encounters the right trigger, it will become metabolically active within minutes and begin growing a new mycelium. The mycelium will eventually mate with another mycelium from the same species through hyphal fusion, forming a hermaphroditic dikaryon in which the two mycelia each have one of the same types of haploid nuclei. The dikaryon can continue sporulating and growing for as long as conditions remain favorable.
In the case of mushroom-forming fungi, this means that they can produce a lot of spores in a short amount of time. The spores are then ejected from the fruiting body through pores or gills, and they will quickly disperse into the surrounding air to start their own new mycelial networks.
The specialized processes and properties that enable fungal spores to form, persist, germinate, and spread across their environments give them enormous power over their surroundings. For example, they can become infectious agents for plants, animals, and humans.
In conclusion, understanding the anatomy of mushrooms is crucial for appreciating their diverse roles in nature and their potential benefits for human health and nutrition. By examining the fruiting body, gills or pores, mycelium, and spores, we can gain a deeper understanding of how these fascinating organisms grow, reproduce, and interact with their environment.
