''Rubroboletus pulcherrimus''—known as ''Boletus pulcherrimus'' until 2015—is a species of mushroom in the family

Boletaceae The Boletaceae are a family of mushroom-forming fungi, primarily characterised by small pores on the spore-bearing hymenial surface (at the underside of the mushroom), instead of gills as are found in most agarics. Nearly as widely distributed ...

. It is a large

bolete {{refimprove, date=July 2020 A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surf ...

from Western North America with distinguishing features that include a netted surface on the stem, a red to brown

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...

and stem color, and red pores that stain blue upon injury. Until 2005 this was the only bolete that has been implicated in the death of someone consuming it; a couple developed gastrointestinal symptoms in 1994 after eating this fungus with the husband succumbing. Autopsy revealed

infarction Infarction is tissue death ( necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from th ...

of the midgut.

Taxonomy

American mycologists Harry D. Thiers and Roy E. Halling were aware of confusion on the west coast of North America over red-pored boletes; two species were traditionally recognised—'' Boletus satanas'' and '' Boletus eastwoodiae''. However, they strongly suspected the type specimen of the latter species was in fact the former. In reviewing material they published a new name for the taxon, which Thiers had written about in local guidebooks as ''B. eastwoodiae'', as they felt that name to be invalid. Hence in 1976 they formally described ''Boletus pulcherrimus'', from the

Latin Latin (, or , ) is a classical language belonging to the 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 the power of the ...

''pulcherrimus'', meaning "very pretty". It was transferred to the genus ''

Rubroboletus ''Rubroboletus'' is a genus of bolete fungi in the family Boletaceae. It was circumscribed by Chinese mycologists in 2014 with '' Rubroboletus sinicus'' as the type species. Species are characterized by having a reddish cap surface, yellow tubes ...

'' in 2015 along with several other allied reddish colored, blue-staining bolete species such as ''B. eastwoodiae'' and ''B. satanas''.

Description

Colored various shades of olive- to reddish-brown, the cap may sometimes reach in diameter and is convex in shape before flattening at maturity. The cap surface may be smooth or velvety when young, but may be scaled in older specimens; the margin of the cap is curved inwards in young specimens but rolls out and flattens as it matures. Boletus pulcherrimus 8405

The cap may reach a thickness of when mature. The adnate (attached squarely to the stem) poroid surface is bright red to dark red or red-brown and bruise dark blue or black; there are 2 to 3 pores per mm in young specimens, and in maturity they expand to about 1 or 2 per mm. In cross section, the tubes and

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, but ...

are yellow. The tubes are between long, while the angular pores are up to 1 mm in diameter; pores can range in color from dark red in young specimens to reddish brown in age. The pores will stain a blue color when cut or bruised. The solid, firm stem is long and thick—up to in diameter, at the base before tapering to at the top. It is yellow or yellow-brown in color and bears a network of red reticulations on the upper 2/3 of its length. The

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 pinkish-tan spore print. A 3.5-centimeter ...

is olive-brown. The taste of the

is reportedly mild, and the odor indistinct, or "slightly fragrant". ; Microscopic characters The

spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

are spindle-shaped or elliptical, thick-walled, smooth, and have dimensions of 13–16 by 5.5–6.5 μm. The

basidia A basidium () is a microscopic sporangium (a spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycelium, developed from secondary mycelium. Tertiary mycelium is highly- ...

, the spore-bearing cells, are club-shaped (clavate), attached to 1 to 4 spores, and have dimensions of 35–90 by 9–12 μm. The

cystidia A cystidium (plural 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 ar ...

(sterile, non-spore-bearing cells found interspersed among the basidia) in the hymenium have dimensions of 33–60 by 8–12 μm.

Clamp connection A clamp connection is a hook-like structure formed by growing hyphal cells of certain fungi. It is a characteristic feature of Basidiomycetes fungi. It is created to ensure that each cell, or segment of hypha separated by septa (cross walls), rec ...

s are absent in the hyphae of ''B. pulcherrimus''.

Similar species

Although the relatively large fruiting bodies of ''R. pulcherrimus'' are distinctive, they might be confused with superficially similar species, such as '' Rubroboletus eastwoodiae''; the latter species has a much thicker stalk. Another similar species is '' R. haematinus'', which may be distinguished by its yellower stem and cap colors that are various shades of brown. Its darker cap and lack of reticulation on the stipe differentiate it from ''R. satanas''. '' Neoboletus luridiformis'' grow with oaks but is smaller and have non-reticulate stipe.

Distribution and habitat

''Rubroboletus pulcherrimus'' is found in western North America, from

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ke ...

and

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

, and may feasibly occur in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Canada. One source notes it grows at low altitudes in the Cascade Range and

Olympic Mountains The Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest at ; however, the easte ...

; another claims it grows at high elevations, over . Fruiting in autumn, it grows singly or in groups (although another source claims "never in groups") in humus in mixed woodlands. In the original publication describing the species, Thiers and Halling note that it is associated with forests containing

tanbark oak ''Notholithocarpus densiflorus'', commonly known as the tanoak or tanbark-oak, is a broadleaf tree in the family Fagaceae, and the type species of the genus ''Notholithocarpus''. It is native to the far western United States, particularly Orego ...

s (''Lithocarpus densiflora''), Douglas fir (''Pseudotsuga menziesii''), and

Grand Fir ''Abies grandis'' (grand fir, giant fir, lowland white fir, great silver fir, western white fir, Vancouver fir, or Oregon fir) is a fir native to the Pacific Northwest and Northern California of North America, occurring at altitudes of sea leve ...

(''Abies grandis'').

Smith Smith may refer to: People * Metalsmith, or simply smith, a craftsman fashioning tools or works of art out of various metals * Smith (given name) * Smith (surname), a family name originating in England, Scotland and Ireland ** List of people wi ...

and Weber mention increased fruitings after warm heavy fall rains following a humid summer.

Toxicity

In general, blue-staining red-pored boletes should be avoided for consumption. Thiers warned this species may be toxic after being alerted to severe gastrointestinal symptoms in one who had merely tasted it. Years later, in 1994, a couple developed

gastrointestinal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

symptoms after eating this fungus and the husband died as a result. A subsequent autopsy revealed that the man had suffered an

of the midgut. ''Rubroboletus pulcherrimus'' was the only bolete that had been implicated in the death of someone consuming it, in: It is known to contain low levels of

muscarine Muscarine, L-(+)-muscarine, or muscarin is a natural product found in certain mushrooms, particularly in '' Inocybe'' and '' Clitocybe'' species, such as the deadly '' C. dealbata''. Mushrooms in the genera '' Entoloma'' and ''Mycena'' have ...

, a

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain ...

toxin. A 2005 report from Australia recorded a fatality from muscarinic syndrome after consuming a mushroom from the genus ''Rubinoboletus''.

References