''Tricholoma equestre'' or ''Tricholoma flavovirens'', also known as man on horseback or yellow knight is a formerly widely eaten but arguably hazardous

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

of the genus ''

Tricholoma ''Tricholoma'' is a genus of fungus that contains many fairly fleshy white-spored gilled mushrooms which are found worldwide generally growing in woodlands. These are ectomycorrhizal fungi, existing in a symbiotic relationship with various s ...

'' that forms

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

with pine trees. Known as ''Grünling'' in German, ''gąska zielonka'' in Polish, ''míscaro'' in Portuguese and ''canari'' in French, it has been treasured as an

edible mushroom Edible mushrooms are the fleshy and edible fruit bodies of several species of macrofungi (fungi which bear fruiting structures that are large enough to be seen with the naked eye). They can appear either below ground ( hypogeous) or above gro ...

worldwide and is especially abundant in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

and

Central Portugal The Central Region ( pt, Região do Centro, ) or Central Portugal is one of the statistical regions of Portugal. The cities with major administrative status inside this region are Coimbra, Aveiro, Viseu, Caldas da Rainha, Leiria, Castelo Branco, ...

. Although it is regarded as quite tasty, cases of

poisoning A poison can be any substance that is harmful to the body. It can be swallowed, inhaled, injected or absorbed through the skin. Poisoning is the harmful effect that occurs when too much of that substance has been taken. Poisoning is not to ...

from eating ''T. equestre'' have been reported. Research has revealed it to have poisonous properties, but these claims are disputed.

Taxonomy and naming

''Tricholoma equestre'' was known to

Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

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 genera. It is the first work to consistently apply binomial names and was the ...

'' in 1753, giving it the name ''Agaricus equestris'', predating a description of ''Agaricus flavovirens'' by

Persoon Christiaan Hendrik Persoon (1 February 1761 – 16 November 1836) was a German mycologist who made additions to Linnaeus' mushroom taxonomy. Early life Persoon was born in South Africa at the Cape of Good Hope, the third child of an immig ...

in 1793. Thus this specific name 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 a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

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, teacher, and scientist in Zerbst, Germany, known chiefly for his contribution to mycological nomenclature. Earlier classification of agarics by pioneering fungal taxonomist Elias Ma ...

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

Greek Greek may refer to: Greece 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 ...

''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 stem is 4–10 cm long and 1–4 wide, is yellow, and brownish at the base. The gills are also yellow colour and the spores are white. The skin layer covering the cap is sticky and can be peeled off.

Toxicity

This species was for a long time highly regarded as one of the tastier edible species (and in some guides still is), and sold in European markets; medieval French knights allegedly reserved this species for themselves, leaving the lowly bovine bolete (''

Suillus bovinus ''Suillus bovinus'', also known as the Jersey cow mushroom or bovine bolete, is a pored mushroom of the genus '' Suillus'' in the family Suillaceae. A common fungus native to Europe and Asia, it has been introduced to North America and Aust ...

'') 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 in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...

. 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 ''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 (also called 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 of ...

, 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 tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compared to hemoglobin, myoglob ...

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

muscle pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another like ...

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, would rule out that this species contains any significant amount of toxic substances.

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 ''Floccularia albolanaripes'' is a species of fungus in the family Agaricaceae. Mushrooms are characterized by their yellow caps with a brownish center and scales over the margin, and the conspicuous remains of a partial veil that is left on the ...

'' and ''F. luteovirens''.

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

Taxonomy and naming

Description

Toxicity

Similar species

See also

Footnotes

External links