Introduction to Fungi, Third Edition

540 HOMOBASIDIOMYCETES
is used in attempts to wean alcoholics from their
addiction, although it is different chemically.
Interference competition involving Coprinus
Many species of Coprinus are coprophilous, typically
with their basidiocarps appearing relatively
late in the succession of fungi on dung (Dix &
Webster, 1995). Certain species are known to
suppress the fruiting of other fungi. A good
example of this phenomenon is C. heptemerus,
which inhibits the fruiting of many species in
nature on rabbit dung and in culture. Its effect
on the sensitive ascomycete Ascobolus crenulatus
was tracked down to the moment when the
hyphae of the two fungi make contact. Within
minutes, the hyphal segment of Ascobolus
touched by a hyphal tip of Coprinus is killed.
There is a rapid loss of turgor, shown by the
bulging of the septa of adjacent cells into the
affected cell, which also loses the ability to
undergo plasmolysis, whilst adjacent cells readily
plasmolyse when bathed in hypertonic fluid.
This form of competition has been termed
hyphal interference or interference competition.
It occurs in a range of genera of coprophilous
basidiomycetes, but is not confined to this ecological
group, having been demonstrated to be
effective also in lignicolous fungi (Ikediugwu &
Webster, 1970a,b; Ikediugwu et al., 1970).
Cell damage is very similar to the effects seen
when self- and non-self hyphae of the same
species confront each other. An oxidative burst is
stimulated and hydrogen peroxide accumulates
in cells of the sensitive partner. This is interpreted
as a defence reaction (Silar, 2005).
19.4.3 Amanitaceae
Amanita (c. 500 spp.)
This is a large and important genus whose
species form sheathing mycorrhiza with trees.
Amanita muscaria (‘fly agaric’; Plate 9a) is often
associated with birch (Betula) but also grows in
mycorrhizal association with Abies, Pinus, Picea,
Quercus and other hosts. As is well known,
the basidiocarps of some species are poisonous,
especially those of A. phalloides (death cap),
A. virosa (destroying angel), A. pantherina (panther
cap) and A. verna, whilst those of A. muscaria are
more hallucinogenic than poisonous. There are
also species whose basidiocarps are excellent to
eat, most notably A. caesarea (Caesar’s mushroom;
Plate 9b), which has been hunted enthusiastically
in Southern European countries since Roman
times. Emperor Claudius was an early connoisseur
of A. caesarea and may have paid for his
mycophagy with his life, probably falling victim
to a poisoned mushroom dish manipulated by
his wife Agrippina in AD 54 (Ramsbottom, 1953).
Other edible species are A. rubescens (blusher),
A. vaginata (grisette) and A. fulva (tawny grisette).
In view of the possible confusion between edible
and poisonous species, it is obviously best to
avoid eating basidiocarps of any whose identity
is uncertain.
The characteristic features of Amanita include
a white spore print and the presence of a volva,
i.e. the torn remnants of a universal veil. The
volva persists as a cup at the base of the stipe and
broken volva fragments may also adhere to the
cap, as seen as the white scales on the red caps of
A. muscaria (Plate 9a). Most species also have
a ring (annulus) on the stem, the remnant of the
partial veil which protected the gills during fruit
body development, but there is no ring in
some species formerly classified in Amanitopsis
(e.g. A. vaginata and A. fulva).
Amanita poisoning
Symptoms after ingestion of fruit bodies of
A. phalloides follow a characteristic time course
over a period of 7 days (Faulstich & Zilker, 1994).
After a mushroom meal and symptom-free
interval (day 1), there is a period of emesis
(vomiting), abdominal cramps and diarrhoea
(day 2), followed by a period of remission (day
3) which is treacherous because it lures many
patients into believing that they have overcome
the poisoning. Meanwhile, severe liver damage is
ongoing and symptoms resume with a vengeance
with gastrointestinal bleeding (day 4), hepatic
encephalopathy (brain damage, day 5), kidney
failure (day 6) and death (day 7).
Amanita poisoning is caused by two toxins,
namely the amatoxin a-amanitin and the
phallotoxin phalloidin (Bresinsky & Besl, 1990;
Wieland & Faulstich, 1991; Chilton, 1994,
Wieland, 1996). Both are bicyclic oligopeptides