Cortinarius rubellus Cooke - Deadly Webcap

Distribution - Taxonomic History - Etymology - Toxicity - Poisoning - Identification - Reference Sources

Cortinarius rubellus - Deadly Webcap

Taxonomy

Phylum: Basidiomycota

Class: Agaricomycetes

Order: Agaricales

Family: Cortinariaceae

Cortinarius rubellus (syn. Cortinarius speciosissimus) is a fairly rare but deadly poisonous mushroom. It is found from late summer to early winter in coniferous woodland and is most common in northerly parts of Europe.

Distribution

Rarely found in the south of England and Wales but becoming increasingly more common as you go further north, this mushroom is very common in Scandinavia and other countries on the mainland of northern Europe. The Deadly Webcap is also found in parts of North America.

Taxonomic History

Cortinarius rubellus - Deadly Webcap, distinctly umbonate

Cortinarius rubellus was described and named by Mordecai Cooke in 1887.

Synonyms of Cortinarius rubellus include Cortinarius speciosissimus Kühner & Romagn, and Cortinarius orellanoides Rob. Henry.

Etymology

The generic name Cortinarius is a reference to the partial veil or cortina (meaning a curtain) that covers the gills when caps are immature. In the genus Cortinarius most species produce partial veils in the form of a fine web of radial fibres connecting the stem to the rim of the cap rather than a solid membrane.

Not surprisingly, the specific epithet rubellus simply means reddish, and the same sense that a red fox is actually reddish brown. Even more obvious is the common name Deadly Webcap, which required no explanation.

Toxicity

This mushroom contains the toxin orellanine, which if eaten destroys the kidneys and liver.

Poisoning incidents, symptoms and treatment

Despite a very different shape, the orange cap of this attractive mushroom has resulted in it being mistaken for Cantharelus cibarius, the highly prized edible Chanterelle mushroom - with serious and in some cases fatal consequences.

A group of Deadly Webcaps, Cortinarius rubellus, only slightly umbonate

The Deadly Webcap is reputedly the poisonous mushroom collected in mistake for chanterelles by Nicholas Evans, famous author of (among other works) 'The Horse Whisperer' - subsequently made into a highly acclaimed film by Robert Redford -and 'The Loop.' Mr Evans and three members of his family suffered serious kidney damage and were hospitalised in Scotland.

The initial symptoms of orellanine poisoning are usually delayed by two or three days, after which flu-like symptoms, headache and vomiting occur. Renal (kidney) failure follows and if not treated can result in death.

Dialysis and other kidney and liver treatments, if received quickly enough, can usually save the lives of people who eat these dangerous Cortinarius mushrooms - as it did in the case of Nicholas Evans - but full recovery is a very long and unpleasant process.

Several other fungi from the Cortinarius genus, including Cortinarius orellanus, are now known to contain the same toxin, and so most experts advise that no webcap fungi should ever be eaten.

Identification guide

Young caps of Cortinarius rubellus

Cap

The tawny-brown to orange cap is at first convex, flattening at maturity but retaining a slight or sometimes pronounced umbo; its surface is dry and slightly scaly.

Cap diameter is typically 4 to 8cm when fully expanded, and the margin is often slightly rolled down even in fully mature specimens.

Gills of Cortinarius rubellus

Gills

The gills, which are covered by a cortina (a cobweb-like veil) in young specimens, are pale yellowish at first, becoming rusty brown as the spores mature.

Stem

Often slightly bowed rather than straight, the stem is usually somewhat paler than the cap and sometimes retains fibres from the cortina, mottled with red; it is fibrous and tapers in slightly towards the base. Stems are typically 7 to 15mm in diameter and 5 to 10 cm tall.

Spores of Cortinarius rubellus

Spores

Ellipsoidal to sub-globose, 9-12 x 6.5-8.5µm; with a rough surface.

Spore print

Rusty reddish-brown.

Basidia of Cortinarius rubellus

Basidia

4-spored.

Odour/taste

Faint smell of raddish. DO NOT TASTE EVEN A SMALL PIECE OF THIS MUSHROOM: it is deadly poisonous and even a small amount can cause serious or even fatal kidney and liver damage.

Habitat

Mycorrhizal with conifer trees - pine and spruce in particular - on damp acid soil; often fruiting in small groups.

Season

August to November in Britain.

Deadly Webcap, New Forest, Hampshire

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2011

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

British Mycological Society, English Names for Fungi

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.