Latin American death cap

Cap

Cap 4-12 cm, convex at first then flattening, whitish to pale olive-grey or greenish-grey, smooth and somewhat viscid when moist, with radial fibrils giving a silky sheen.

Colour is unreliable as a sole field mark - pale white to yellow-green forms all occur.

Gills / Pores

Gills white, free, crowded. Spore print white.

Stem

Stem 6-14 cm, white, bearing a fragile white pendant ring that may shred and collapse.

The bulbous base is wrapped in a sac-like white volva - the single most important feature - that is frequently buried and easily lost when the mushroom is pulled up carelessly.

Smell & taste

Odour is mild in fresh specimens; older ones develop a faint sweetish-unpleasant smell.

Amanita arocheae is responsible for a significant proportion of fatal mushroom poisonings in Mexico and Central America. Because it grows in regions where edible Amanita and Volvariella species are traditionally harvested, the risk of misidentification is high.

Poisoning incidents have been documented in Oaxaca and other Mexican states, in Guatemala and Costa Rica, and in Colombia.

If any amount of arocheae has been eaten, call emergency services immediately - do not wait for symptoms. Bring the mushroom remains or a photograph.

Treatment requires:

• hospital admission
• IV fluids
• silibinin (silymarin)
• N-acetylcysteine
• in severe cases, liver transplantation

There is no antidote once liver failure begins.

Amatoxins (principally alpha-amanitin), the same class of cyclopeptide toxins as in Amanita phalloides.

Alpha-amanitin inhibits RNA polymerase II, shutting down protein synthesis in liver and kidney cells.

Heat-stable: no cooking method renders the mushroom safe.

Latency 6-24 hours after ingestion. The delayed onset is characteristic and means victims often do not connect their illness with the meal.

1. 1Phase 1 (6-24 h): severe nausea, vomiting, profuse watery diarrhoea and abdominal cramps.
2. 2Phase 2 (1-3 days): apparent recovery - the patient may feel better, but liver and kidney damage is progressing silently.
3. 3Phase 3: acute liver failure, coagulopathy, hepatic encephalopathy and renal failure; without intensive medical care death follows within 4-8 days.

A single mushroom can contain a lethal dose for an adult.

A single mushroom can deliver a lethal dose to an adult.

The 6-24 hour latency between eating and first symptoms means victims frequently do not connect the meal with the illness - do not wait for symptoms to appear before seeking help.

If there is any possibility of ingestion, call emergency services immediately and bring the mushroom or a photograph.

No preparation method - boiling, frying, drying, fermenting - removes the toxins.

In the field, never harvest any pale-gilled mushroom in Neotropical oak or cloud forest without fully exposing the base. The sac-like volva is the single most important safety character and is easily left in the ground if the fruiting body is snapped rather than dug.

Mycorrhizal with oaks (Quercus) and tropical broadleaf hardwoods in montane and premontane cloud forests, from Mexico through Central America and into the northern Andes of South America.

It grows on well-drained mineral soils in both mature forest and forest edges, and can appear in coffee plantations or shaded gardens where native oaks remain.

The wet season in the Neotropics (broadly May-November), peaking at the height of the rainy season in June-September.

Altitude and local rainfall timing shift fruiting by weeks.

Solitary or in small groups, emerging from a buried volva.

Mycorrhizal, so it recurs in the same spots around the same host trees year after year.

It often appears when the rains are well established and soil moisture and warmth are both high.

Wet-season ectomycorrhizal fruiter; flushes follow sustained rainfall once soil is warm. At higher montane elevations (1500-2500 m) fruiting concentrates in June-September; at lower premontane sites it can extend from May through November.

Young button-stage specimens can be confused with edible Volvariella volvacea (paddy straw mushroom), which also has a volva but lacks a ring and has pink gills and a brown-pink spore print.

Local edible Amanita species such as Amanita rubescens can superficially resemble arocheae at early stages, but rubescens reddens where damaged and has a non-saccate volva.

The introduced Amanita phalloides (European death cap) also occurs in South America around ornamental and planted trees. Both phalloides and arocheae are deadly and can be confused with each other; phalloides tends more greenish-yellow, arocheae more pallid-grey, but colour is unreliable.