''Butyriboletus fuscoroseus'' is a pored mushroom in the family

Boletaceae The Boletaceae are a Family (biology), family of mushroom-forming fungi, primarily characterised by small pores on the spore-bearing hymenium, hymenial surface (at the underside of the mushroom), instead of Lamella (mycology), gills as are found ...

. It was formerly considered a species of ''

Boletus ''Boletus'' is a genus of mushroom-producing fungi, comprising over 100 species. The genus ''Boletus'' was originally broadly defined and described by Carl Linnaeus in 1753, essentially containing all fungi with hymenial pores instead of gills. ...

'', but in 2014 was transferred to the newly created genus ''

Butyriboletus ''Butyriboletus'' is a genus of fungi in the family Boletaceae. The genus was circumscribed in 2014 by mycologists David Arora and Jonathan L. Frank to accommodate "butter bolete" species that were shown by molecular phylogenetics, molecular anal ...

''. ''Boletus pseudoregius'', a European taxon originally described as a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

of '' Boletus appendiculatus'' in 1927, is a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

. ''B. fuscoroseus'' is considered

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

in the Czech Republic.

Description

''Butyriboletus fuscoroseus'' produces a robust

basidiocarp In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do no ...

with a convex cap ( pileus) up to 20 cm across. Young caps are hemispherical before flattening, and display colours ranging from violet-brown to reddish-brown, occasionally dull red; older specimens often fade to beige with a faint pink tint. The margin typically retains remnants of the

partial veil In mycology, a partial veil (also called an inner veil, to differentiate it from the "outer", or universal veil) is a temporary structure of tissue found on the fruiting bodies of some Basidiomycota, basidiomycete fungus, fungi, typically agarics. ...

(appendiculate). Beneath the cap, the

tubes Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/electronica producers Arndt Röri ...

measure up to 1.5 cm long and are bright yellow, developing an olive tinge with age; both tubes and pores bruise blue when handled. The stipe is stout, up to 10 cm long and 3 cm thick, cylindrical to club-shaped, yellow near the apex and tinged pink to red towards the base, usually with a well-developed reticulation of the same colour; it too bruises blue on handling. The context (

flesh Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, ...

) is whitish in the cap and lemon yellow in the stipe, shading to clay pink at the stipe base and turning blue on exposure. The odour is indistinct in young fruit bodies but in maturity may become medicinal or paint-like, and when dried can resemble smoked meat or chicory; taste is mild to slightly acidic. Microscopically, the

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s are

ellipsoid An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional Scaling (geometry), scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a Surface (mathemat ...

, measuring about 10–14.5 × 4–5.5

micrometre The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a uni ...

s (μm), each containing one to three large oil droplets. The

basidia A basidium (: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies are also ...

(spore-bearing cells) are club-shaped and four-spored, and the

cystidia A cystidium (: cystidia) is a relatively large cell found on the sporocarp of a basidiomycete (for example, on the surface of a mushroom gill), often between clusters of basidia. Since cystidia have highly varied and distinct shapes that are o ...

measure roughly 36–52 × 9–14.5 μm. The cap surface (

pileipellis The pileipellis is the uppermost layer of hyphae in the pileus of a fungal fruit body. It covers the trama, the fleshy tissue of the fruit body. The pileipellis is more or less synonymous with the cuticle, but the cuticle generally describes ...

) is a trichoderm of interwoven, slightly incrusted

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e with rounded terminal cells. Chemical spot tests produce only slight reactions with

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

(NH₄OH) and

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

(KOH) solution, and no change with

iron(II) sulphate Iron(II) sulfate or ferrous sulfate (British English: sulphate instead of sulfate) denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7), but several values for ...

(FeSO₄) or

Melzer's reagent Melzer's reagent (also known as Melzer's iodine reagent, Melzer's solution or informally as Melzer's) is a chemical reagent used by mycologists to assist with the identification of fungi, and by phytopathologists for fungi that are plant pathogens ...

Habitat and distribution

The fruiting bodies of ''Butyriboletus fuscoroseus'' develop in warm, dry to moderately moist broadleaf woodlands, most often under oak (''

Quercus An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

'' spp.), and frequently on

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

soils at elevations from near sea level up to about 800 m. In Bulgaria, it typically appears from June through September, corresponding with the summer season. Within Bulgaria, confirmed localities extend along the Southern

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...

coast, the Eastern Forebalkan, the western and eastern flanks of the

Stara Planina The Balkan mountain range is located in the eastern part of the Balkan peninsula in Southeastern Europe. It is conventionally taken to begin at the peak of Vrashka Chuka on the border between Bulgaria and Serbia. It then runs for about , first ...

mountains, the

Sofia Sofia is the Capital city, capital and List of cities and towns in Bulgaria, largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Is ...

region and the Eastern

Rhodope Rhodope may refer to: * Rhodope (mythology), several figures of Greek mythology * Rhodope Mountains, in Bulgaria and Greece * Rhodope (regional unit), of Greece * Rhodope (province), a Roman and Byzantine province * 166 Rhodope, an asteroid * Rhodop ...

range. Beyond Bulgaria, it occurs across much of southern and central Europe—including Austria, Belgium, Czech Republic, France, Greece, Hungary, Italy, Spain and the Balkan states—and its range reaches into Turkey.

References

{{Taxonbar , from1=Q26203758 , from2=Q11774727 fuscoroseus Fungi described in 1912 Fungi of Europe Fungus species