Agaricus abruptibulbus

Agaricus abruptibulbus is a species of mushroom in the genus Agaricus. It is commonly known as the abruptly-bulbous agaricus or the flat-bulb mushroom.

Physical characteristics

Cap:

Diameter: 5-15(18) cm.

Shape: Conical to convex-cuboid, then broadly convex to subflattened.

Color: Pale to dark gray-brown, especially dark at the center.

Texture: Smooth but breaking up into very fine scales or fibrillates when dry.

Margin: Sometimes long curved, sometimes slightly appendiculate with velar remains.

Young and fresh caps may be fleetingly bright yellow when crumpled.

Gills:

Free and distant from the stem.

Initially pale, briefly pink, then turning chocolate brown.

With entire awns.

Stem:

Length: 7-15 x 0.8-1.5(3) cm.

Slender, even to attenuated towards the apex.

Abruptly bulbous-marginate, flattened.

Whitish to cream, yellowing when crushed.

Initially stuffed, then becoming hollow.

Partial Veil:

Membranous, very elastic, white.

Leaves a pendulous ring.

Thin, very large, and persistent.

May exude droplets that turn brown with age.

Flesh:

Moderately thick, white.

Yellowing to slowly browning when cut.

Smell and Flavor:

Aniseed smell.

Pleasant flavor.

Spore Characteristics:

Dark brown to purple brown spores.

Spore size: 6-8 x 4-5 µm.

Basidia often with 4 sterigmata.

Cheilocystids:

Abundant, often subglobose to ovoid.

Thin-walled.

Size: (8.5)12.5-19.5 x (8)10-16 µm.

Ecology:

Saprotrophic (feeds on decaying organic matter).

Typically found on the forest floor, especially under coniferous trees.

Period of Growth:

August to October.

Frequency:

Occasional.

Chemical Reactions:

The mushroom's cap turns yellow with KOH (potassium hydroxide).

Agaricus abruptibulbus Edibility

Edible of choice but with caution. Consuming Agaricus abruptibulbus that has bioaccumulated cadmium can potentially be dangerous to your health. Cadmium is a toxic heavy metal, and its ingestion, especially in elevated concentrations, can lead to serious health issues. Cadmium toxicity primarily affects the kidneys and can also harm other organs. Therefore, if you know or suspect that the Agaricus abruptibulbus you have collected has grown in an environment with high cadmium pollution or has accumulated significant levels of cadmium, it is advisable to avoid eating it. Cadmium contamination is a serious concern, and the risks associated with consuming mushrooms with high cadmium content outweigh any potential benefits of consuming the mushroom.

Cadmium bioaccumulation

The ability of Agaricus abruptibulbus to bioaccumulate cadmium, a toxic heavy metal, is indeed a fascinating and unique characteristic. Bioaccumulation is the process by which an organism, in this case, a mushroom, accumulates and retains higher levels of a particular substance (in this case, cadmium) from its environment, often at concentrations greater than what is found in the surrounding soil or substrate. This property is of interest for several reasons:

Environmental Indicator: The ability of some mushroom species to accumulate heavy metals such as cadmium makes them valuable indicators of environmental contamination. Monitoring the cadmium levels in these mushrooms can provide insights into soil pollution and environmental quality.

Tolerance and Growth Stimulation: The observation that Agaricus abruptibulbus can not only accumulate cadmium but also experience growth stimulation in the presence of this heavy metal is intriguing. It suggests a level of tolerance or even a potential benefit to the mushroom in a cadmium-rich environment.

Cadmium-Binding Proteins: The presence of a low molecular weight metal-binding protein named "cadmium-mycophosphatin" is a significant finding. This protein may play a role in the mushroom's ability to sequester and manage cadmium. Understanding the mechanisms behind this interaction is important for both environmental and biotechnological applications.

Bioremediation Potential: The ability of certain mushroom species to accumulate heavy metals has led to research on their potential use in bioremediation, which is the process of using living organisms to clean up contaminated environments. In this case, mushrooms like Agaricus abruptibulbus could be employed to remove or sequester cadmium from polluted soil or water.

Simmilar spieces

Agaricus arvensis (The Horse Mushroom): Similar in appearance and edibility, but differences in features like the cap and spore size might help distinguish it.

Agaricus silvicola (Wood Mushroom): As mentioned, there may be some debate regarding the differentiation of A. abruptibulbus and A. silvicola, so comparing characteristics carefully is essential.

Agaricus campestris (The Meadow Mushroom): Another edible Agaricus species that is often found in grassy areas.

Agaricus semotus: A species within the Arvenses clade that is closely related to A. silvicola and may share similar characteristics.

References

1. MycoMatch (MatchMaker) Mushrooms of the Pacific Northwest
Version 2.4.1. 2023.