Satan's Bolete

Appearance

The compact cap can reach an impressive 30 cm, extraordinarily 40 cm, very rarely 50 cm in diameter. At first it is hemispherical with an inrolled margin, but becomes convex at maturity as the fruit body expands, while in older specimens the margin might be slightly undulating. When young, the pileus is greyish white to silvery-white or buff, but older specimens tend to develop olivaceous, ochraceous or brownish tinges. The surface of the cap is finely tomentose, becoming smooth at maturity and is often slightly viscid in wet weather. The cuticle is tightly attached to the flesh and does not peel.

The free to slightly adnate tubes are up to 3 mm long, pale yellow or greenish yellow and bluing when cut. The pores are rounded, yellow to orange at first, but soon turning red from the point of their attachment to the stem outwards, eventually becoming entirely purplish red or carmine-red at full maturity and instantly bluing when touched or bruised. The stipe is 5–15 cm, extraordinarily 20 cm, very rarely 25 cm long, distinctly bulbous , and often wider than its length, becoming more ventricose as the fungus expands but remaining bulbous at the base.

Its colour is golden-yellow to orange at the apex, becoming increasingly pinkish-red to reddish-orange further down and deep carmine-red to purple-red towards the base. It is decorated in a fine, yellowish to reddish hexagonal net, sometimes confined to the upper half of the stipe. The flesh is thick, spongy and whitish, but may be yellow to straw-coloured in immature specimens and is sometimes reddish at the stem base. It slowly turns a faded blue colour when cut, bluing more intensely around the apex and above the tubes. The smell is weak and pleasantly musky in young fruit bodies, but becomes increasingly putrid in older specimens, reminiscent of carrion. Young specimens have a reportedly pleasant, nutty taste. The spore print is olivaceous green.

The spores are fusiform when viewed under a microscope and measure 10–16 × 4.5–7.5 μm. The cap cuticle is composed of interwoven septate hyphae, which are often finely incrusted.

Naming

Both ''Rubroboletus satanas'' and ''Suillellus luridus'' are known as ''ayimantari'' in eastern Turkey.Satan's bolete can be confused with a number of other species:

⤷ ''Rubroboletus rhodoxanthus'' is found predominantly on acidic soil, develops pinkish tinges of the cap, has a more or less cylindrical or clavate stipe with a very dense, well-developed net and lemon-yellow flesh that distinctly stains blue only in the cap when longitudinally sliced.
⤷ ''Rubroboletus legaliae'' is also acidophilous, has pinkish tinges on the cap, flesh that stains more extensively blue when cut and narrower spores, measuring 9–15 × 4–6 μm.
⤷ ''Rubroboletus pulchrotinctus'' has a variable cap colour often featuring a pinkish band at the margin, has a dull-coloured stipe without deep red tinges, pores that remain yellow or orange even in mature fruit bodies and somewhat narrower spores, measuring 12–15 × 4.5–6 μm.
⤷ ''Rubroboletus rubrosanguineus'' is associated with spruce or fir , has pinkish tinges on the cap and smaller spores, measuring 10–14.5 × 4–6 μm.
⤷ ''Caloboletus calopus'' is usually associated with coniferous trees, has pores that remain persistently yellow even in overripe fruit bodies, has a more slender, cylindrical or clavate stipe and narrower spores, measuring 11–16 × 4–5.5 μm.

Distribution

''Rubroboletus satanas'' is widely distributed throughout the temperate zone, but is rare in most of its reported localities. In Europe, it mostly occurs in the southern regions and is rare or absent in northern countries. It fruits in the summer and early autumn in warm, broad-leaved and mixed forests, forming ectomycorrhizal associations with oak and sweet chestnut , with a preference for calcareous soils. Other frequently reported hosts are hornbeam, beech and lime.

In the United Kingdom, this striking bolete is found only in the south of England. It is rare in Scandinavia, occurring primarily on a few islands in the Baltic Sea where conditions are favourable, with highly calcareous soil. In the eastern Mediterranean region, it has been reported from the Bar'am Forest in the Upper Galilee region of northern Israel, as well as the island of Cyprus, where it is found in association with the narrow-endemic golden oak . It has further been documented in the Black Sea and eastern Anatolia regions of Turkey,as well as Crimea and Ukraine, with its distribution possibly extending as far south as Iran.

In the past, ''R. satanas'' had been reported from the coastal areas of California and the southeastern US, however, these sightings are instead of the closely related species ''Rubroboletus eastwoodiae''.

Defense

Satan's bolete is poisonous, especially if eaten raw. The symptoms, which are predominantly gastrointestinal in nature, include nausea, abdominal pain, violent vomiting and bloody diarrhoea that can last up to six hours. A 2012 study on mushroom poisonings in Switzerland by Katharina M. Schenk-Jaeger and colleagues, found ''Rubroboletus satanas'' to have caused severe gastrointestinal symptoms, including recurrent vomiting and bloody diarrhoea.

The toxic enzyme bolesatine has been isolated from fruiting bodies of ''R. satanas'' and implicated in the poisonings. Bolesatine is a protein synthesis inhibitor and, when given to mice, causes massive thrombosis. At lower concentrations, bolesatine is a mitogen, inducing cell division in human T lymphocytes. Muscarine has also been isolated from the fungus, but the quantities are believed to be far too small to account for its toxic effects. More recent studies have associated the poisoning caused by ''R. satanas'' with hyperprocalcitonemia, and classified it as a distinct syndrome among fungal poisonings.

Controversially, English mycologist John Ramsbottom reported in 1953 that ''R. satanas'' is consumed in certain parts of Italy and the former Czechoslovakia. In those regions, the fungus is reportedly eaten following prolonged boiling that may neutralise the toxins, though this has never been proven scientifically. Similar reports exist from the San Francisco Bay Area of the United States, but probably involve a different fungus misidentified as ''R. satanas''. Ramsbottom speculated that there may be a regional variation in its toxicity, and conceded that the fungus may not be as poisonous as widely reported. Nevertheless, ''R. satanas'' is rarely sampled casually, not least because of the putrid smell of its mature fruiting bodies, which in addition to their bright colours and blue staining, make the fungus unappealing for human consumption.