Inocybe praetervisa — Overlooked fibrecap, overlooked fiberhead
Overlooked fibrecap2, photograph by Adolf Ceska.
Overlooked fibrecap13 photograph by Adolf Ceska.
Overlooked fibrecap12 showing gills and expanded bulb at base of stem, photograph by Adolf Ceska.
Overlooked fibrecap11, A. Habit; B. Cystidia; C. Basidiospores Inocybe praetervisa, sketches by Oluna Ceska.
Odour: Unknown.
Cap: 3–6 cm in diameter, conical when young, becoming flatter with age, usually with a knob (an umbo) in the middle. Colour orange-brown or yellowish-brown, sometimes paler around the margins. The surface is fibrillose, with radial cracks.
Gills: Close together, narrow and narrowly adnate; initially cream, becoming brownish as spores mature. Seen with a hand lens, gill edges are often paler than the sporulating gill surfaces.
Stems: 4–7 cm long x 0.4–1.0 cm wide, initially white, upper half often with a slight fuzz (pruinose, visible with hand lens), sometime becoming brown with drying. The base of the stipe is often marginate, which means that it flares out abruptly into a wider bulb at its base (see the photo above).
Ring: None obvious.
Cup: None.
Spores: 8–13 (14) x 6–8.5 µm, brown. Spores have 8–11 knobs; if you squint, their profiles look like animal crackers or gummy bears! See the sketch above.
Cystidia: Elongate, thick-walled cells and shaped somewhat like bottles with a cap of minute crystals. They are located on the gills. See the sketch above.
Habitat: On forest floor under Douglas fir (Pseudotsuga menziesii), grand fir (Abies grandis), and other conifers on Vancouver Island, British Columbia and probably elsewhere in the Pacific northwest. The species reportedly grows in mixed boreal forests in Europe, but due to difficulties with identification, the host range is poorly known3. Ectomycorrhizal.
Confirmed geographical distribution: BC, Italy, Spain5. Likely elsewhere in Europe and North America but this is difficult to confirm because records of occurrence of this species are so frequently based on misidentified specimens. Barcode DNA sequences are needed to verify specimen identity.
The overlooked fibrecap is perhaps one of the more common fibrecaps in BC coastal Douglas fir forests in summer. The flat-topped bulb at the base of its stem helps identify it. The shape and size of its microscopic cystidia and its relatively large, knobby basidiospores further rule out many alternative identifications. However, BC and the Pacific northwest are rich in as-yet undescribed Inocybe species.
Toxins7: Inocybe praetervisa probably contains muscarine8. Muscarine is a cholinergic toxin. It acts by mimicking the neurotransmitter acetylcholine and interfering with normal transmission of nerve impulses to smooth muscles. The presence of knobby spores (see sketch) in vomit would be good evidence that a fibrecap in this general group was eaten and that muscarine was causing the poisoning symptoms. However, many muscarine-containing fibrecaps have smooth spores so the absence of knobs on spores does not rule out poisoning by a fibrecap.
Symptoms9: Time of onset usually between 15 min and 2 hours, occasionally 5 hours or longer, usually ending in 24 hours. 'SLUDGE' symptoms result, Salivation, Lacrimation (excess tear formation); Urination; Diarrhoea; Gastrointestinal upset; Emesis (vomiting)10.
Treatment11: Contact your regional Poison Control Centre if you or someone you know is ill after eating fibrecaps. Poison centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.
Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.