Sarah Brown
Mushrooms are known for their distinctive gills, which are the papery hymenophore ribs found under the cap of some mushroom species, most often agarics. These gills serve as a means of spore dispersal and are important for species identification. The formation of gills increases the surface area available for spore production, with some species exhibiting a 20-fold increase in surface area due to the presence of gills. The gills are also involved in the ejection of spores, either through a mechanism called Ballistospory or Buller's drop, which involves the formation of a water droplet that forcibly ejects the spores into the air. While most mushrooms rely on gravity for spore dispersal, some species have evolved gills that enhance the efficiency of this process. The variety of gill shapes, spacing, and arrangements contributes to the diversity of mushroom species, with some gills even producing latex. Understanding the role of gills in mushrooms provides insights into their reproductive strategies and evolutionary adaptations.
| Characteristics | Values |
|---|---|
| Purpose of gills | Used by mushrooms as a means of spore dispersal |
| Gills' surface area | Relative to a flat surface, the formation of gills increased the hymenium surface by a factor of 7.0 (lowest) in Russula citrina and 20.0 (highest) in Agaricus campestris |
| Spore dispersal | Spores are ejected out of the gills through a process called Ballistospory |
| Gravity's role | Most spores are not sticky, so they simply fall out of the gills |
| Types of gills | True gills, false gills, and partial gills |
| True gills | Refers to the structure of the fertile surface ("hymenium") that continues uninterrupted over the gill edge |
| False gills | Refers to rudimentary lamellar structures that are little more than folds, wrinkles, or veins |
| Partial gills | Lamellulae are partial gills that do not reach the stipe |
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What You'll Learn
Gills increase the surface area for spore production
The presence of gills in mushrooms is a result of evolution. The gills, or lamellae, are papery hymenophore ribs found under the cap of some mushroom species, most often agarics. They are used by the mushrooms as a means of spore dispersal and are important for species identification.
The formation of gills increases the hymenium surface area, which is the spore-producing surface. Buller (1909) found that relative to a flat surface, the formation of gills increased the hymenium surface area by a factor of 7.0 in Russula citrina (the lowest increase) and 20.0 in Agaricus campestris (the highest increase). This increase in surface area allows for a greater number of spores to be produced, which can then be forcibly ejected from the gills into the air.
The spacing between the gills is also important for the successful release of spores. The spores are propelled horizontally from the gill surface by a mechanism called the surface tension catapult and then fall vertically between the gills before reaching the airflow swirling underneath the cap. The branching of the gills and the addition of lamellulae (small lamellae filling gaps between gills) further increase the surface area for spore production.
The evolution of gills in mushrooms has likely occurred through convergent evolution, where similar structures evolved separately in different species. This is supported by the diversity of gill anatomy and development in mushroom-forming fungi. The formation of gills greatly increases the surface area for spore production, which may explain why this morphology has been selected for during evolution.
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Gravity and force are needed to eject spores from gills
Mushrooms have gills as a means of spore dispersal. The gills, or lamellae, are papery hymenophore ribs under the cap of some mushroom species, most often agarics. The spores are developed on the spore-producing hymenium, which is organised on the surface of the gills.
Gravity and force are indeed needed to eject spores from gills. Firstly, the spores are microscopic and have very little mass, so they require a significant amount of force to be ejected. The spores experience over 5000 Gs of force when shot out of the mushrooms. This process is called ballistospory.
Additionally, while gravity is a factor, it is not the only force at play. Mushrooms use ballistospory to eject spores out of their gills forcefully. This mechanism involves the basidia (the sexual reproductive structure where spores are developed) producing Buller's drop, a water droplet that causes the spores to be forcibly ejected off the basidia and into the air.
The gills also play a role in maximising the surface area for spore production. The branching of gills can increase the surface area by up to 20 times compared to a flat surface, allowing for more efficient spore production and dispersal.
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Gills are important for species identification
The structure of the gills can also provide clues about the evolution of the fungus. For instance, the presence of false gills in the related genera of chanterelles, Cantharellus and Craterellus, suggests that these structures are an intermediate step in the evolution of true gills. The patchy distribution of lamellate basidiomata across the phylogeny of mushroom-forming Agaricomycetes also indicates that the morphology of gills has likely evolved independently in different fungal lineages.
Furthermore, the arrangement and spacing of gills can have important functional implications for successful spore release. Buller's classic experiments in 1909 demonstrated that the formation of gills increased the surface area available for spore production, with the highest increase observed in Agaricus campestris (a 20-fold increase relative to a flat surface). The spacing between gills is also important for the effective release of spores, as demonstrated by Turner and Webster in 1991 who showed that spores are propelled horizontally from the gill surface by a mechanism called the surface tension catapult.
The presence or absence of gills can also provide information about the toxicity of a mushroom species. For example, the Deadly Webcaps (Cortinarius rubellus), native to Northern Europe, and the Deadly Dapperling, found in parts of Europe and Asia, are both gilled mushrooms known to contain amatoxins. On the other hand, some of the most toxic mushrooms, such as the Destroying Angels (Amanita verna) and the Galerina marginata, are not gilled. Therefore, while gills can provide important clues about species identification, other features and characteristics must also be considered for accurate identification and assessment of toxicity.
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'False gills' are folds, wrinkles or veins
False gills, also known as rudimentary lamellar structures, are found in members of the two related genera of chanterelles: Cantharellus and Craterellus. These false gills are distinguishable from "true gills" as the structure of the fertile surface, or hymenium, continues uninterrupted over the gill edge. Thus, false gills are essentially folds, wrinkles, or veins that do not significantly increase the surface area for spore production.
False gills are considered primitive lamellae that provide insight into the evolution of true gills. While they do not possess the same spore-dispersing functionality as true gills, false gills indicate that the evolution of gill-like structures occurred independently in different fungal lineages. This is known as convergent evolution, where similar structures arise separately rather than from a shared anatomical feature.
The presence of false gills in certain mushroom species, such as Cantharellus, Craterellus, and Gomphus, showcases the gradual development of gill-like structures. These false gills may have evolved into more complex structures in response to the need for increased spore production and dispersal efficiency.
The distinction between false gills and true gills lies in the continuity of the hymenium, which is the spore-producing surface. In false gills, the hymenium extends beyond the gill edge, blurring the distinct gill formations. This structural difference results in reduced efficiency in spore dispersal compared to true gills, which are optimized for maximizing surface area and facilitating spore release.
In summary, false gills are folds, wrinkles, or veins that represent an intermediate stage in the evolution of gills in mushrooms. Their presence in certain species highlights the diverse anatomical adaptations that have arisen independently in different fungal groups. By studying false gills, mycologists gain valuable insights into the evolutionary trajectory of gill development and its impact on spore production and dispersal strategies in fungi.
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Gills are formed by multiple orders within the Agaricomycetes
Gills are a key feature of mushrooms, and they are formed by multiple orders within the Agaricomycetes, a class of fungi that includes most of the familiar mushroom-forming species. The presence of gills is one of the key characteristics used to identify and classify mushrooms, and they play a
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Frequently asked questions
Mushrooms have gills as a means of spore dispersal. The gills increase the surface area for spore production and help in the identification of the species.
The spores are ejected out of the gills using a mechanism called the surface tension catapult. Some mushrooms also produce a water droplet called "Buller's drop" that causes the spores to be forcibly ejected into the air.
The formation of gills increases the surface area for spore production. Relative to spore production over a flat surface, gills achieve a maximum 20-fold increase in surface area.
No, not all mushrooms have gills. While gills are important for species identification, there are other categories of undersides besides gills.
In mycology, a gill is called a lamella (plural: lamellae). Lamellulae are small lamellae that fill the gaps between gills as the radius of the cap grows.
