''Tricholoma equestre'' or ''Tricholoma flavovirens'', commonly known as the man on horseback or yellow knight, is a species of

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

of the genus ''

Tricholoma ''Tricholoma'' is a genus of fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms ...

'' that forms

ectomycorrhiza An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobio ...

with pine trees. It has been treasured as an

edible mushroom Edible mushrooms are the fleshy fruit bodies of numerous species of macrofungi (fungi that bear fruiting structures large enough to be seen with the naked eye). Edibility may be defined by criteria including the absence of poisonous effect ...

worldwide and is especially abundant in

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

and

Central Portugal The Central Region (, ) or Central Portugal is one of the statistical regions of Portugal. The cities with major administrative status inside this region are Coimbra, Aveiro, Viseu, Leiria, Castelo Branco and Guarda. It is one of the seven Regi ...

. Although it is regarded as quite tasty, cases of

poisoning Poisoning is the harmful effect which occurs when Toxicity, toxic substances are introduced into the body. The term "poisoning" is a derivative of poison, a term describing any chemical substance that may harm or kill a living organism upon ...

from eating the species have been reported from Europe.

Taxonomy

''Tricholoma equestre'' was known to

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, who officially described it in Volume Two of his ''

Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genus, genera. It is the first work to consistently apply binomial nomenclature ...

'' in 1753, giving it the name ''Agaricus equestris'', predating a description of ''Agaricus flavovirens'' by Persoon in 1793. Thus this

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

meaning "of or pertaining to horses" in

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

takes precedence over ''Tricholoma flavovirens'', the other scientific name by which this mushroom has been known. It was placed in the genus ''

'' by German

Paul Kummer Paul Kummer (22 August 1834 – 6 December 1912) was a Minister (Christianity), minister, teacher, and scientist in Zerbst, Germany, known chiefly for his contribution to mycological botanical nomenclature, nomenclature. Earlier Taxonomy (biology), ...

in his 1871 work ''Der Führer in die Pilzkunde''. The generic name derives from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''trichos''/τριχος 'hair' and ''loma''/λωμα 'hem', 'fringe' or 'border'. Common names include the ''man-on-horseback'', ''yellow knight'', and ''saddle-shaped tricholoma''.

Description

The cap ranges from in width and is usually yellow with brownish areas, particularly at the centre. The skin layer covering the cap is sticky and can be peeled off. The yellow stem is 4–10 cm long and 1–2 cm wide, and brownish at the base. The gills are also yellow and the spores are white, producing a white

spore print 300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing warm orange ("tussock") color spore print. ...

Similar species

It can easily be mistaken for a variety of other members of the genus ''Tricholoma'', such as '' T. auratum'', '' T. aestuans'', '' T. intermedium'', '' T. sejunctum'', and '' T. sulphureum''. Other similar species include '' Floccularia albolanaripes'' and '' F. luteovirens''.

Toxicity

This species was for a long time highly regarded as one of the tastier

edible An edible item is any item that is safe for humans to eat. "Edible" is differentiated from " eatable" because it does not indicate how an item tastes, only whether it is fit to be eaten. Nonpoisonous items found in nature – such as some mushroo ...

species (and by some authors still is) and was sold in European markets. Medieval French knights allegedly reserved this species for themselves, leaving the lowly bovine bolete ('' Suillus bovinus'') for the peasants. Concern was first raised in southwestern France. People who have been poisoned have all had three or more meals containing ''T. equestre'' within the last two weeks prior to treatment. One to four days after their last meal containing the fungus, the patients reported weakness of the muscles, sometimes accompanied by pain. This weakness progressed for another three to four days accompanied by a feeling of stiffness and darkening of the

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

. Periods of nausea, sweating, reddening of the face were also registered, but there were no fevers. As yet, there have been no reported cases of poisoning in North America, and there is speculation that the respective mushrooms may in fact be different species that are very similar in appearance. Molecular research shows that multiple species may have been identified as the synonym ''T. flavovirens'' on the West Coast. There are reports where patients treated for ''T. equestre'' poisoning have died, likely as a result of the poisoning. The poison in this mushroom has remained unknown. The basic mechanism of poisoning is suspected to be

rhabdomyolysis Rhabdomyolysis (shortened as rhabdo) is a condition in which damaged skeletal muscle breaks down rapidly. Symptoms may include muscle pains, weakness, vomiting, and confusion. There may be tea-colored urine or an irregular heartbeat. Some o ...

, damaging of the cell membrane of skeletal muscle fibres. In this disorder, the oxygen-carrying muscular protein

myoglobin Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle, skeletal Muscle, muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compar ...

is released and appears in urine, resulting in symptoms such as

muscle pain Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, espec ...

and brownish coloration of the urine. A 2018 research conducted in Poland with the recruitment of ten healthy volunteers, who ate 300 grams per head (about twice the normal dose) of fried ''T. equestre'' in a single meal, with no reported consequences or alterations. However, a 2020 systematic review highlights several studies indicating elevated plasma creatine kinase (CK) pro-inflammatory activities, in addition to its effect on other liver function biomarkers, underlining a cause for concern and suggestions "not to harvest and consume this species". From the same 2020 study, they registered the same level of plasma CK using different edible mushrooms. For example the same level obtained by ''T. equestre'' was also obtained by ''

Boletus edulis ''Boletus edulis'' (English: cep, penny bun, porcino) is a basidiomycete fungus, and the type species of the genus ''Boletus''. It is prized as an edible mushroom. The fungus produces Basidiospore, spore-bearing basidiocarp, fruit bodies ...

''.

In culture

It is known as ''Grünling'' in German, ''gąska zielonka'' in Polish, ''míscaro'' in Portuguese and ''canari'' in French.

Footnotes

External links

Food for Thought: Mushrooming Concerns
"Science News Online" article on ''T. flavovirens'' (''T. equestre'').

"About Health Canada" article on ''Tricholoma equestre'' poisoning.

A report on a few new kinds of mushroom poisoning.
Riddarmusseronen kan vara giftig
Swedish article on ''T. flavovirens'' and its toxicity.
Matportalen: Matsoppen som ble giftsopp
Norwegian article on ''T. equestre''. {{Taxonbar, from=Q312756 equestre Fungi described in 1753 Fungi of Europe Poisonous fungi Taxa named by Carl Linnaeus Fungus species