Bay-liver webcap

Mystinarius badiohepaticus is a medium-sized webcap recognised in the field by two features working together: the viscid, glutinous cap that gleams when wet, and the characteristic two-tone colouration - a rich chestnut-bay to liver-brown centre contrasting with a paler buff to tan margin.

The name could hardly be more descriptive: 'badius' is Latin for bay or chestnut-brown, 'hepaticus' for liver-coloured.

Cap

When fresh and young, the cap has an almost lacquered, deep reddish-brown centre that lightens conspicuously toward the edge; as the cap ages or dries, this contrast diminishes and the whole cap fades toward ochre-tan.

The cobwebby cortina stretched between the cap margin and upper stem is the genus-level identification marker for all webcaps - look for it in young specimens before the veil collapses, and for the rust-stained zone it leaves on the stem in mature specimens.

Gills

The gills begin pale buff and reliably turn rust-brown as spores ripen.

This shift from pale gills to rust-brown is universal across the Cortinarius sensu lato family (now including Mystinarius) and is the most reliable feature distinguishing any webcap from superficially similar mushrooms: a rusty-brown spore print combined with a collapsed cobweb veil means webcap, every time.

Although no confirmed fatal poisoning case is attributed specifically to Mystinarius badiohepaticus in the published medical literature, the danger of this species derives not from its own confirmed lethality but from three compounding factors:

1. 1Its membership in a family with multiple confirmed deadly species.
2. 2Its occurrence in the same habitat as those confirmed-deadly species.
3. 3The impossibility of distinguishing safe from toxic Cortinariaceae by any field method.

The deadly Cortinarius rotundisporus and C. archeri - both confirmed orellanin-bearers - grow in the same southeastern Australian and New Zealand native forests, and foragers who misidentify a dangerous webcap as this species face potentially lethal kidney failure.

The appropriate response to encountering any webcap-type mushroom in Australasian native forest is not to eat it, regardless of the apparent species identity.

If ingestion of any webcap is suspected, seek emergency medical care immediately from a poisons centre - do not wait for symptoms.

Mystinarius badiohepaticus belongs to the family Cortinariaceae, which contains the most nephrotoxic fungi known.

The archetypal toxin of the family is orellanin - a polypyridine N-oxide that selectively destroys the proximal tubule cells of the kidneys, through a mechanism involving superoxide radical generation and inhibition of protein synthesis.

Orellanin is heat-stable and completely resistant to all standard food preparation methods. It has been confirmed analytically in multiple Australasian Cortinarius sensu lato species occurring in the same native forest habitat as Mystinarius badiohepaticus.

Published chemical analysis specifically for M. badiohepaticus (formerly Cortinarius badiohepaticus) is limited, and orellanin has not been confirmed in this species by name.

However, the precautionary consensus among Australasian mycological authorities is that all Cortinariaceae in native forest should be treated as carrying full orellanin-class risk until proven otherwise. This is the only defensible position given the severity of the syndrome and the absence of reliable field tests for orellanin.

Orellanin poisoning is defined by its extraordinarily prolonged latency - typically two to three weeks, and documented up to six weeks or more in some cases.

This delay is the defining and most dangerous feature: the victim may feel entirely well for weeks while progressive, irreversible destruction of renal tubular cells is occurring asymptomatically beneath the surface.

When symptoms finally emerge they are non-specific:

• Intense thirst
• Increased urination progressing paradoxically to decreased urination
• Nausea
• Vomiting
• Headache
• Severe fatigue
• Loss of appetite
• Pain in the back or flanks

These signs reflect developing acute kidney injury. Untreated, the condition progresses to oliguric or anuric renal failure requiring dialysis.

The extreme latency also complicates diagnosis: physicians examining a patient with unexplained kidney failure weeks after a foray may not be told about a mushroom meal, or the connection may not be made.

If any Cortinariaceae has been consumed - including species resembling Mystinarius badiohepaticus - inform medical staff immediately, even if the meal was weeks ago.

DO NOT EAT. Mystinarius badiohepaticus must be treated as a dangerous poisonous species.

The species belongs to the Cortinariaceae - the family responsible for the greatest number of mushroom-related kidney failures in the world - and grows in the same native Australian and New Zealand forest as confirmed orellanin-bearing deadly species.

No field test can confirm whether a given specimen of this or any similar species carries nephrotoxic compounds. The toxin, if present, is fully heat-stable and cannot be removed by any cooking method.

The characteristic delayed onset of orellanin poisoning means that ingestion of even a small amount can lead to severe, potentially irreversible kidney damage that does not become apparent for weeks.

If you suspect any webcap-type mushroom has been eaten, contact the Poisons Information Centre immediately without waiting for symptoms:

• Australia 13 11 26
• New Zealand 0800 764 766

This is a native ectomycorrhizal species of Australasian forests that cannot grow without a living host tree.

On the Australian mainland it associates primarily with Eucalyptus and Corymbia in dry to moist sclerophyll forest; in cooler, wetter sites in Tasmania and in New Zealand it extends into Nothofagus (southern beech) forest.

These habitat preferences mean it is always found in intact native forest with established old-growth or mature-regrowth trees - it will not appear in gardens, pine plantations, or farmland.

Among leaf litter on the forest floor, look for it in shaded positions where soil holds moisture between rain events. It fruits singly or in small scattered groups from established mycelial mats that may be decades old beneath the soil surface.

Fruiting occurs through Southern Hemisphere autumn and into early winter, broadly March to July, with the main flush in April-May.

The trigger is the arrival of significant post-summer rainfall combined with cooling soil temperatures - as air temperatures fall after summer, soil temperatures begin descending through the 10-16 °C range that most ectomycorrhizal Cortinariaceae favour.

In practice this means watching for the first substantial autumn rain event (20+ mm over one to two weeks) after the long dry Australian summer. Fruiting bodies typically emerge 10-20 days after the triggering rain event.

In higher-altitude or wetter sites in Tasmania and New Zealand, fruiting can continue into June or July; at low-elevation mainland sites the season is compressed into April-May.

The species is absent in spring and summer.

Like all ectomycorrhizal fungi, Mystinarius badiohepaticus spends most of its life as a network of fungal hyphae woven into the fine absorptive roots of its host trees - a partnership in which the fungus supplies the tree with soil minerals (particularly phosphorus) in exchange for photosynthate (sugars).

This relationship can persist for many years or decades, and the same patch of forest floor may produce fruit bodies each autumn from the same mycelial network.

What foragers see above ground - the cap, gills, stem - is only the reproductive structure, the equivalent of a fruit on a tree.

Fruit bodies appear singly or in small scattered groups; dense clustering is not characteristic of this species.

Southern Hemisphere autumn species. Fruiting triggered by substantial post-summer rainfall (20+ mm over 14 days) as soil temperatures drop below approximately 16 °C. Flush lag typically 10-20 days after triggering rain event. Peak April-May; may extend to June-July at higher-altitude or wetter sites in Tasmania and New Zealand. Absent in spring and summer.

The most dangerous confusion is with other brown webcaps in the same habitat:

• Cortinarius rotundisporus (deadly, orellanin confirmed)
• C. archeri (deadly, orellanin confirmed)
• C. australiensis (deadly, orellanin confirmed)

All three occur in southeastern Australian and New Zealand native forest and share the rusty-brown spore print, cobwebby cortina, and Cortinariaceae growth habit.

Where Mystinarius badiohepaticus is brown-to-liver coloured, these deadly species tend toward violet or blue-violet, but colour varies with age, weather conditions, and individual specimen variation to an extent that colour alone cannot be trusted as a separator.

The only reliable distinction from these deadly species requires spore measurement and chemical analysis by a specialist.

Galerina marginata (deadly, amatoxin) is another deadly native-forest webcap with rusty-brown spores and a ring zone on the stem, but is much smaller (cap typically 1-4 cm), grows in dense clusters on dead wood or buried wood, and has a true membranous ring rather than a cortina ring-zone.

Hebeloma crustuliniforme and related Hebeloma species (inedible/toxic) have brown caps but lack viscidity, have a mealy-fishy smell, brown (not rusty cinnamon) spore prints, and no cortina remnant.

Pholiota and Flammulina species with brown caps lack the Cortinariaceae viscid-glutinous surface and have a ring rather than cortina.