Rubroboletus pulcherrimus
Description
Rubroboletus pulcherrimus (until 2015 known as Boletus pulcherrimus) is a species of mushroom in the family Boletaceae. It is a large bolete from Western North America with distinguishing features that include a netted surface on the stem, a red to brown cap and stem color, and red pores that stain blue upon injury. It is found in western North America, from New Mexico and California to Washington, and may feasibly occur in British Columbia, Canada.
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 symptoms after eating this fungus and the husband died as a result. A subsequent autopsy revealed that the man had suffered an infarction of the midgut. Rubroboletus pulcherrimus was the only bolete that had been implicated in the death of someone consuming it, It is known to contain low levels of muscarine, a peripheral nervous system toxin. A 2005 report from Australia recorded a fatality from muscarinic syndrome after consuming a mushroom from the genus Rubinoboletus.
Common names:Red-Pored Bolete.
Mushroom Identification
Cap
9-17 cm broad, convex, expanding to broadly convex; margin incurved when young, then decurved, often wavy, overlapping the pore surface; surface dry, uneven or pitted, matted-tomentose, at maturity occasionally appressed fibrillose-squamulose, in dry weather patchy-areolate; color: dull-brown to cream-brown, the pigments often mottled, frequently tinged reddish towards the margin; context cream-yellow, 3.0-4.0 cm thick at maturity, soft, bluing when cut, sometimes erratically, larval tunnels vinaceous; odor not distinctive; taste mild.
Hymenophore
Pores dull red, shading to reddish-orange at the margin, in age reddish-brown, when young, 2-3 per mm, 1-2 per mm at maturity, bluing when bruised; tubes up to 1.0 cm long, dull yellow-green, bluing when injured, adnate in youth, eventually depressed at the stipe.
Stipe
7.0-14.0 cm long, up to 8.0 cm thick at the base, clavate, gradually narrowing toward the apex; upper two-thirds of stipe covered with vinaceous-red reticulations over a pallid background, bruising blue, the stipe base dingy-buff, matted-tomentose, becoming blackish-brown where handled; context firm, fleshy, cream-yellow, sometimes pale-vinaceous at the base, the upper portion bluing when cut or injured, worm holes edged vinaceous.
Spores
13.0-15.5 x 5.0-6 µm, smooth, moderately thick-walled, narrowly ellipsoid in face-view, spindle-shaped in profile; hilar appendage inconspicuous.
Spore Print
Brown to dull olive-brown.
Habitat
Solitary to scattered in mixed hardwood/conifer woods; known from coastal forests north of San Francisco; fruiting from late fall to early winter.
Look-Alikes
Rubroboletus eastwoodiae
Similar, but it can be distinguished by an abruptly bulbous stipe, and short, squat stature. Microscopically, these two species are also distinct, the spores of Boletus pulcherrimus averaging several microns longer than those of B. satanas.
Suillellus amygdalinus and Boletus erythropus
They are differentiated from B. pulcherrimus by smaller size and nonreticulate stipes. Rubroboletus pulcherrimus was known for many years as B. eastwoodiae, a name which became invalid for this species when a study of the type collection proved it to be a specimen of what we had been calling B. satanas.
Rubroboletus haematinus
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.
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Grow with oaks but is smaller and have non-reticulate stipe.
History
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 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 pulcherrimus, meaning "very pretty". It was transferred to the genus Rubroboletus in 2015 along with several other allied reddish colored, blue-staining bolete species such as B. eastwoodiae and B. satanas.
Photo sources:
Photo 1 - Author: Ryane Snow (snowman) (CC BY-SA 3.0)
Photo 2 - Author: Ryane Snow (snowman) (CC BY-SA 3.0)
Photo 3 - Author: Darvin DeShazer (CC BY-SA 3.0)
Photo 4 - Author: MStruzak (CC BY-SA 3.0)
