Fungal Fragrance

 

Published in: Spore Prints - Bulletin of the Puget Sound Mycological Society #459, p.4, February 2010
 
Offbeat Fungal Fragrances
By Daniel Winkler

December's Spore Prints article by Brian Luther regarding fungal odors was highly informative and very interesting. I am happy to see that after retirement Brian can dedicate even more time to fungal research and that he is sharing his insights with us. Personally, I always smell mushrooms, whether to help identification, try to label an odor or just to experience an interesting aroma.
 
However, in his long listing of smells Brian omitted one of the most common and evocative odors, the spermatic smell, which is quite common among fungi. Using Matchmaker, a free software tool for keying out PNW mushrooms, especially helpful when searching for a fungal identity by using smells, one just needs to open the odor page and check one of the 71 smells listed. Checking the “spermatic” box, 75 mushroom species will pop up. The list is very diverse and includes species of the following genera: Cortinarius, CystodermaGalerinaHygrophorusHypholomaInocephalusInocybe (42 species!)LepistaLeptoniaLeucopaxillusLyophyllumMelanoleucaMycenaMyxomphaliaPholiota, and Russula. Please note that so far Matchmaker's odor search function only works for gilled mushrooms and there might be non-gilled mushrooms oozing this smell as well [Brian's list of garlic & onions scented fungi included only a fraction of gilled mushrooms, most alliaceous smelling fungi were actually truffles]. Furthermore, double checking on Matchmaker's list, not all mushrooms listed as having a spermatic odor contain this trait. For example, the Hygrophorus species are just described as smelling of green corn.
 
Talking about odors it is important to remember that our olfactory sense is by far not as well developed as our sense of sight and it is sadly feeble compared to that of many animals. Even if we can smell certain odors it does not mean we could label them. Furthermore, some people can not detect certain smells and often are not aware of such a lack of olfactory capacity, since we do not conceptualize smells like many other environmental stimuli. Mushrooms however, use chemicals to communicate, although what we might be smelling [or tasting] might not be messenger chemicals, since our olfactory sense is not very sensitive and tiny amounts seem sufficient for communication between fungi. Less subtle are the communication efforts of truffles to help animals to sniff them out underground so that they will spread their spores. And interestingly the aroma of a mature culinary truffles ready to be eaten and spread is á-Androstenol, a sex pheromone that attracts sows, since it is usually in the saliva of rotting boars. This illustrates that the scent of fungi changes through their life-cycle, just like the multitude of scents produced by humans vary through their stages of life or their activities of day or night.
 
Interestingly, besides mushrooms I also came across several shrubs and trees, which produce profusely this odor when in flower. Most often I detect it from Rowans or Mountain ashes (Sorbus sitchensis, S. aucuparia etc.) I have encountered in the mountains of North America, Europe and High Asia. These white-flowering small trees of the Rose family (Rosaceae) have a circumpolar distribution growing commonly in subalpine habitats. Another white-flowering, spermatic smelling Rosaceae is Ocean spray (Holodiscus discolor), which is a common shrub in coastal PNW forests. Susan Goldhor, after reading the manuscript, pointed out to me that Ginkgo (Ginkgo biloba) also shares this scent as does the edible European chestnut (Castanea sativa) in the beech family (Fagaceae) in flower. Interestingly Joe Ammirati describes the odor of several Inocybe - Fiber caps as “reminiscent of catkins of chestnut”, which other label as spermatic.
 
However, I think I am onto something much bigger here, and yes, size matters. In short I suspect some mycologists are still unnecessarily inhibited about facing our human, or maybe more general our animal nature. In several mushroom guides, even recent ones, mushrooms with a spermatic smell are simply described as smelling disgusting or even putrid, two smells not found in Matchmaker's odor listing. I do not want to be too judgmental, and I realize that many of us may be struggling with absurd Victorian ideas of decency. One can argue about smells just like about taste, somebody's favorite food triggers drooling in one person and gagging reflex in another person. However, science is not helped by expecting mushroom guide users to recognize the spermatic odor in terms as general as disgusting or disagreeable. It might as well be described by terms as very natural, earthy or intense. Such evasive classification just reeks of repressed sexuality or maybe even a sad love life, when the smell of the male reproductive essence is associated with negative memories and not with blissful experiences.
 
It is no coincidence that this odor is present in the context of reproduction in humans, plants and fungi alike [the mushroom being the spore producing organ of the fungus]. When it comes to the odor of human sperm, and I was not able to find a study on this odor in mushrooms, four amino acids seem to be major players: spermidine, spermine, putrescine and cadaverine. This does not sound like an assortment of truly fragrant substances. However, they also represent a line of decay and probably spermidine and spermine smell much less offensive than what I fantasize to be the odor of putrescine and cadaverine. Also some people argue that this smell should be rather referred to as “semenatic” and not spermatic, but that is just semantics. However we want to call it, in fungi this odor is at least an odor I can clearly identify and thus helps me to identify a mushroom with the right keys.
 
All this points me to the conclusion that the chemicals responsible for the spermatic smell must have been around for a long, long time, since this smell is to be found in reproductive processes in such divergent organisms as animals, plants, fungi and also bacteria. And it turns out that spermidine and spermine have important functions in metabolic processes. Spermidine reduces aging in immune cells of yeasts, insects and humans and spermine seems to protect nucleic acids. I would not be surprised if there are other life forms that also carry that smell in reproductive processes, but do not expect me to start smelling out insects, algae, slime molds and bacteria. For me it is sufficient to call a spade a spade, and use whatever characteristics there are to recognize all things alive [and throbbing].
 
 
About the author
Daniel Winkler grew up collecting wild mushrooms in the Alps. He received a Diploma (= master) in Geography, Ecology, and Biology at FU Berlin. He lives in Kirkland, Washington, and works as researcher and NGO consultant on environmental issues of the Tibetan Plateau and Himalayas. He has published on forest ecology, forestry, land use, medicinal plants and fungi [see www.danielwinkler.com].
Working in Tibet, Daniel realized that mushrooms play a crucial role in Tibet. Since 1998, he has been researching Tibet's diverse mushroom industry and its importance for rural people, and he also leads “MushRoaming” tours to Tibet [visit www.mushroaming.com].

Posted: April 25, 2010
Last edited Thu, 09/06/2012 - 12:56