| Tricholoma ustale | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Agaricales |
| Family: | Tricholomataceae |
| Genus: | Tricholoma |
| Species: | T. ustale |
| Binomial name | |
| Tricholoma ustale | |
| Synonyms[1] | |
| |
Tricholoma ustale, commonly known as theburnt knight, is aspecies ofmushroom in the large genusTricholoma. It is found in Asia, Europe, and North America, though those from North America may represent one or more different species.[2]
Elias Magnus Fries described the fungus in 1818 asAgaricus ustalis.[3]Paul Kummer gave it its current name in 1871 upon transferring it to the genusTricholoma.[4]Lucien Quélet'sGyrodon ustale, published in 1886,[5] is asynonym.[1]Marcel Bon described thevarietyrufoaurantiacum from France in 1984.[6] Within the genusTricholoma,T. ustale isclassified in thesectionAlbobrunnea of thesubgenusTricholoma.[7]
Thespecies name is from theLatinustalis "burnt" and relates to the colour of the mushroom.[2] It iscommonly known as the "burnt knight".[8] In Japan, the mushroom is known asKakishimeji (Kaki-shimeji).[9]
The mushroom has a bell-shape to conical or convexcap that measures 3–10 cm (1.2–3.9 in) in diameter and is orange-red-brown. The cap margin is initially curled inward, but straightens in age as the edge become lobed wavy. Thegills are somewhat crowded together and have anadnate toemarginate attachment to thestem. They are cream to pale yellow when young, aging to pale brown with brown spots. The cylindrical stem, which measures 3–9 cm (1.2–3.5 in) long by 1–2.5 cm (0.4–1.0 in) thick, is somewhat thicker at the base. Theflesh is white but turns brown where it is bruised or otherwise injured. The roughly spherical to ellipsoidspores are typically 6.0–7.5 by 5.0–6.0 μm, and feature ahilum.[3]
Tricholoma ezcarayense, described from Spain in 1992, is similar in appearance toT. ustale, and also grows in association with beech. It can be distinguished in the field by its less robust stature, the minute, flat scales on the cap, and the green tints present in the reddish-brown colour of the cap. It can be more reliably distinguished by microscopic characteristics, as thehyphae in itscap cuticle have abundantclamp connections, unlikeT. ustale.[7]
Tricholoma ustale is one of the three species most commonly implicated withmushroom poisoning in Japan[10] (Other two areOmphalotus japonicus andEntoloma rhodopolium). Consumption of the mushroom causes gastrointestinal distress, including symptoms such as vomiting and diarrhoea.[9] Chemical analysis of Japanese populations has revealed the toxic principlesustalic acid and several related compounds. Force-fed to mice, ustalic acid causes them to sit still in a crouched position, hesitant to move, and induces tremors and abdominal contractions. High enough concentrations of the toxin (10 milligrams per mouse) cause death.[9] Ustalic acid, an inhibitor of the sodium-potassium pump (Na+/K+-ATPase) found in theplasma membrane of allanimal cells, has beenchemically synthesized.[11] The toxicity of North American populations is unknown.[2]
Tricholoma ustale is anectomycorrhizal species, and grows in association withbeech. In England, it can be locally common in the southerncounties.[7]