and memories are stored, odors of any kind can trigger recollections of past encounters with secondarily defended prey that did not end well.33,2
A 1983
study that tested opossums’ reactions to Agaricus bisporus (the common button mushroom) treated with both an innocuous “mushroomy” volatile and the tasteless and odorless poison muscimol found that once the opossums associated illness with the treated mushrooms, they subsequently rejected, without tasting, all other untreated and muscimol laced A. bisporus. However, memories of the association did not last; after three months the opossums forgot about the odor as a warning signal and ate muscimol-treated and untreated mushroom alike.27
Maybe, the
short-term memory was enough given the short season and life spans of many mushrooms. Variable pungency in odor emissions
Figure 25. Amanita porphyria, Grey- veiled Amanita, is a nondescript poisonous mushroom with a radish smell. Although not unpleasant, does this distinct smell signal the mushroom’s unprofitability? Photo Pieter van Heerden.
Although field studies designed to test
olfactory aposematism in mushrooms are scarce, a 2005 study using cross- species comparisons of hundreds of mushrooms in European and North American guide books claimed that poisonous mushrooms are more likely to smell “unpleasant” (as judged by humans and maybe other mammals) than edible ones.29
is common in mushrooms and might, for different reasons, be important during the various stages of mushroom development.5
When spore-bearing
structures (gills, pores, and spines) develop, it is in the mushroom’s best interest to emit odors to discourage the premature consumption of unripened spores. During the adult stage when the spores are ripe, varying the odor might encourage mycophages to feed and aid spore dispersal. Some mushrooms are known to vary the pungency of their odors during various development stages, but whether this is an adaptation for spore dispersal, or a result of depleted resources remains an open question.29
It has been suggested
that olfactory aposematism might be especially important in white mushrooms. While a connection between being poisonous and white is true for some mushrooms (Figs. 24 and 25), it is not true for others—a situation that contributes to many accidental mushroom poisonings each year.32
Conclusions Te ability to detect and respond to
Consequently, there is no reliable
connection between odor and edibility other than pungency in odor might make the mushroom less appetizing, but not necessarily poisonous. Research has also shown that odors do not have to be unpleasant to be effective signals of unprofitability. Since they are processed in the same area of mammalian brains where emotions
odors is a primordial sensory ability common to most organisms across all kingdoms; most organisms, including fungi, use their chemical senses to explore and make sense of their environment. Fungi also use their elaborate bouquets to communicate readiness to mate, to establish various kinds of relationships with plants, microbes, and other fungi, and to attract vectors to disperse their spores. Fungi may also use odors to trigger olfactory flashbacks in animals to avoid predation. Life, it seems, communicates and cooperates as much— if not more—than it competes; perhaps odor may be the universal language between organisms, one we are beginning
Fall 2021 FUNGI Volume 14:4 53
to decipher only now.
Acknowledgments Special thanks to Andrus Voitk for
reviewing the article, and to those mycologists and photographers who made their mushroom images freely available. Tis article originally appeared in
Omphalina (Vol. 11, no.4), the newsletter of the Foray Newfoundland and Labrador.
References Cited
1. Schulz-Bohm, K., L. Martín-Sánchez, and P. Garbeva. 2017. Microbial volatiles: small molecules with an important role in intra- and inter- kingdom interactions. Frontiers in Microbiology (published online) doi:10.3389/fmicb.2017.02484
2. Hoover, K.C. 2010. Smell with inspiration: the evolutionary significance of olfaction. American Journal of Physical Anthropology 143(Suppl 51): 63–74. doi:10.1002/ ajpa.21441
3. Rowan, D.D. 2011. Volatile
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