Cortinarius xiphidipus

A medium to large brown-capped webcap.

Cap

Cap 4-10 cm across, convex at first then broadly umbonate or flat with a low boss. Dull ochre-brown to tawny rust-brown, smooth and slightly greasy when moist, drying paler.

Flesh

Firm, pale buff to ochre, unchanged on cutting.

Gills

Attached, crowded, initially ochre then rust-brown as spores mature. Spore print rusty-brown.

The cortina - a fine cobweb of white fibres covering the gills when young - is the genus hallmark; its spore-stained remnant on the stipe forms a distinctive rusty-brown ring zone.

Stem

4-9 cm × 1-2 cm, fibrillose, whitish to pale brown.

Smell & taste

Odour faintly earthy or indistinct.

The combination of rusty-brown spores, cortina remnants, and mycorrhizal habit under Nothofagus defines the genus here.

High. Even a single moderate serving can cause permanent renal damage.

The long delay to symptom onset means the causal link to mushroom consumption is often missed by treating physicians. Always inform emergency services of possible Cortinarius ingestion if any webcap has been consumed and renal symptoms develop weeks later.

There is no antidote; treatment is supportive.

Given the incompletely characterised Cortinarius flora of South America, no regional webcap species should ever be consumed.

Orellanin (suspected; consistent with the broader Cortinarius taxonomy). This heat-stable, water-soluble compound causes nephrotoxic renal tubular necrosis.

It is not destroyed by cooking, drying, or other food preparation.

The latency period of 2-21 days (rarely up to 3 months) before symptom onset is the most dangerous aspect, as it prevents clear causal attribution.

• Early phase (days 1-7): may be asymptomatic, or mild nausea, thirst, and abdominal discomfort.
• Intermediate phase (1-3 weeks): flu-like symptoms, excessive thirst, frequent urination, nausea, headache, fatigue.
• Late phase (2-8 weeks): progressive renal failure with reduced urine output, severe fatigue, back and flank pain, nausea, and vomiting.

Severe cases progress to anuric renal failure requiring dialysis. Hepatotoxicity is sometimes also observed.

Cortinarius xiphidipus contains orellanin, or is at minimum suspected to contain nephrotoxic compounds consistent with the orellanin family.

Orellanin is a bicyclic peptide, unique among fungal toxins for its extreme delay between ingestion and the onset of symptoms: kidney failure typically manifests 2-3 weeks (sometimes up to 3 months) after eating the mushroom, long after the meal is forgotten.

By the time renal impairment is diagnosed, the damage may be severe and irreversible, sometimes requiring dialysis or kidney transplant. No antidote exists. Even small amounts can cause permanent injury.

The genus Cortinarius as a whole contains hundreds of species; safe identification to species level requires microscopic examination and expert knowledge. Any brown agaric with a rusty-brown spore print and cobweb-veil remnants must be treated as a potential orellanin-containing webcap.

The RULE: do not eat any Cortinarius in southern South America.

Grows singly or in scattered groups on the forest floor under Nothofagus (southern beech), in the Patagonian and Valdivian temperate rainforests of southern Chile and adjacent Argentina.

Prefers humid, shaded sites with deep leaf litter and slightly acidic soils.

Like all webcaps, it is strictly ectomycorrhizal - its mycelium threads through the roots of Nothofagus trees in a partnership that can span decades, and it simply cannot fruit without that living tree connection.

Southern Hemisphere autumn: March through June, peaking April-May.

Fruiting is triggered by the cooling that follows late-summer rains. Soil temperatures dropping below 12-14 °C and sustained soil moisture from autumn rainfall combine to initiate the main flush.

Solitary or in small scattered groups on humus-rich forest soil; it does not form dense clusters.

Because it is mycorrhizal, the fungus lives unseen for most of the year as mycelium woven into Nothofagus roots. When autumn conditions are right, fruiting bodies push up from the same spots year after year, marking where those underground partnerships run.

Mycorrhizal webcap; fruiting triggered by sustained autumn rainfall and cooling soils below 13 °C in the Patagonian and Valdivian forest belt. Flush lag is longer than for saprotrophic species. Estimates follow general cortinarioid ecology.

Several dangerous confusion risks exist in Patagonian forests.

1. 1Cortinarius rubellus (deadly) and Cortinarius orellanus (deadly) - primarily Northern Hemisphere but serve as a reference for the hazard pattern: rust-brown spore print, cortina veil remnants, and earthy smell with no distinctive chemical odour. If a foraged brown mushroom under beech shows a rusty-brown spore print and cobweb-veil remnants, it is a webcap and must not be eaten.
2. 2Descolea antarctica and other Descolea species - brown caps and brown spores, growing under southern beech; they are similarly inedible or of unknown toxicity.
3. 3Pholiota-like species with brown scales and ring, separated by their lack of a cobweb cortina and their preference for decaying wood rather than soil.
4. 4Cortinarius caperatus (Gypsy mushroom, edible in Europe) - this species does occur in South America and is considered edible, but it should never be collected based solely on resemblance to a known edible without expert confirmation, as webcap species can share the same habitat.