What's already in the scientific literature?
Here's an excerpt from my graduate student first year exam, where I was asked to complete a brief review of the literature to provide background for my project proposal. Technical language is used, so I'll define some terms beforehand:
mycoparasite = a fungus which parasitizes other fungi
basidiomycete = a fungus belonging to Phylum Basidiomycota, a large evolutionary group of fungi containing most "mushrooms"
sporocarp = fruiting body (the actual "mushroom" seen aboveground)
taxa = groups of organisms (singular is "taxon")
entomopathogen = an organism which parasitizes insects (often meant to refer to arthropods in general)
ectomycorrhizal = a fungus exhibiting a mutually beneficial association with tree roots
mycelium = the underground network of thin cells called "hyphae" which comprise the fungal organism
anamorph = the asexual part of a fungal lifecycle, often mistaken for a completely different organism than the teleomorph (sexual part of the lifecycle). Not all fungi are separated into anamorph and teleomorph
“Lobster mushrooms” are a popular edible mushroom endemic to North America, easily spotted on the forest floor due to their bright orange coloration (Rochon et al. 2009). These conspicuous “lobsters” are understood to be a composite of two distinct fungi: a mycoparasitic mold of the species Hypomyces lactifluorum and the basidiomycete sporocarp that it attacks. Traditionally, these sporocarps were expected to belong exclusively to Russula brevipes (Rogerson & Samuels 1994) but other hosts within Russula and Lactarius have since been identified (Rochon et al. 2009). Hypomyces belongs to the Order Hypocreales (Phylum Ascomycota), which contains other parasitic taxa such as the mycoparasite Escovopsis (Man et al. 2016), which specializes on the fungal cultivars of attine ants, and the entomopathogen Ophiocordyceps (Rogerson 1970). Russula and Lactarius hosts belong to the major mushroom-forming Class Agaricomycetes (Phylum Basidiomycota) and are both known to be ectomycorrhizal on a wide variety of tree species (Rochon et al. 2009).
The genus Hypomyces contains mycoparasites with varying apparent degrees of specialization. Within the boleticolous (bolete-parasitizing) species of Hypomyces there is diversity in extent of specialization, but many are restricted to a certain family or genus (Rogerson & Samuels 1989; Douhan & Rizzo 2003). Agaricicolous (agaric-parasitizing) Hypomyces also range in demonstrated specificity with the many genus-specific members, such as H. hyalinus on Amanita, contrasting with the narrow host preference of H. lithuanicus for Lactarius torminosis (Rogerson & Samuels 1994).
The transformation of the host sporocarp by H. lactifluorum is one of the more visually dramatic extended phenotypes caused by Hypomyces parasites, as lobster mushrooms are characterized by their bright orange color and twisted, deformed shape caused by the parasite mycelium covering the sporocarp (Laperriere et al. 2018). Aborted gill tissue of the host is replaced by the parasite (Spooner & Roberts 2005), for which there is no known anamorph (Rogerson & Samuels 1994). “Albino” infections of Russulaceae resembling lobster mushrooms have been identified as H. macrosporus, a separate species closely resembling H. lactifluorum but distinguished by color and chemistry (Rogerson & Samuels 1994). However, this classification of apparent white morphs of H. lactifluorum as a separate species has not been corroborated with molecular data.
The edibility of the lobster mushroom stands in stark contrast to the unpalatable taste of the uninfected Russula brevipes sporocarp. Laperriere et al. (2018) found that compared to uninfected Russula brevipes, the lobster mushroom sporocarp has a notable absence of terpenoids and a marked increase in lipids, characteristics that explain the increased gustatory appeal of the parasitized fruiting body. No other Hypomyces-infected sporocarp is known to be edible (Laperriere et al. 2018). Spore dispersal by vertebrate ingestion and subsequent defecation is well-established for truffle-forming fungi, and could be an explanation for the unusually palatable and conspicuous extended phenotype of H. lactifluorum infection.
Commercial lobster mushroom consumption is based on wild-harvesting operations, as cultivation has been unsuccessful (Berch et al. 2007). Better characterization of the parasitic association that creates the lobster mushroom complex could improve sustainability of wild-harvesting, as well as give insight into fungal diseases of cultivated mushrooms such as Agaricus bisporus.
References:
Berch, S. M., Ka, K.-H., Park, H., & Winder, R. (2007). Development and potential of the cultivated and wild-harvested mushroom industries in the Republic of Korea and British Columbia. Journal of Ecosystems and Management, 8(3). Retrieved from http://jem-online.org/forrex/index.php/jem/article/view/372
Douhan, G. W., & Rizzo, D. M. (2003). Host-parasite relationships among bolete infecting Hypomyces species. Mycological Research, 107 (11), 1342–1349. https://doi.org/10.1017/S0953756203008542
Laperriere, G., Desgagné-Penix, I., & Germain, H. (2018). DNA distribution pattern and metabolite profile of wild edible lobster mushroom (Hypomyces lactifluorum/Russula brevipes). Genome, 61(5), 329-336.
Rochon, C., Pare, D., Khasa, D. P., & Fortin, J. A. (2009). Ecology and management of the lobster mushroom in an eastern Canadian jack pine stand. Canadian journal of forest research, 39(11), 2080-2091.
Rogerson, C. T. (1970). The Hypocrealean Fungi (Ascomycetes, Hypocreales). Mycologia, 62(5), 865–910. https://doi.org/10.1080/00275514.1970.12019033
Rogerson, C. T., & Samuels, G. J. (1989). Boleticolous Species of Hypomyces. Mycologia, 81(3), 413–432. https://doi.org/10.2307/3760079
Rogerson, C. T., & Samuels, G. J. (1994). Agaricicolous Species of Hypomyces. Mycologia, 86(6), 839–866. https://doi.org/10.2307/3760597
Spooner B., & Roberts, P. (2010). Fungi. UK: HarperCollins.
mycoparasite = a fungus which parasitizes other fungi
basidiomycete = a fungus belonging to Phylum Basidiomycota, a large evolutionary group of fungi containing most "mushrooms"
sporocarp = fruiting body (the actual "mushroom" seen aboveground)
taxa = groups of organisms (singular is "taxon")
entomopathogen = an organism which parasitizes insects (often meant to refer to arthropods in general)
ectomycorrhizal = a fungus exhibiting a mutually beneficial association with tree roots
mycelium = the underground network of thin cells called "hyphae" which comprise the fungal organism
anamorph = the asexual part of a fungal lifecycle, often mistaken for a completely different organism than the teleomorph (sexual part of the lifecycle). Not all fungi are separated into anamorph and teleomorph
“Lobster mushrooms” are a popular edible mushroom endemic to North America, easily spotted on the forest floor due to their bright orange coloration (Rochon et al. 2009). These conspicuous “lobsters” are understood to be a composite of two distinct fungi: a mycoparasitic mold of the species Hypomyces lactifluorum and the basidiomycete sporocarp that it attacks. Traditionally, these sporocarps were expected to belong exclusively to Russula brevipes (Rogerson & Samuels 1994) but other hosts within Russula and Lactarius have since been identified (Rochon et al. 2009). Hypomyces belongs to the Order Hypocreales (Phylum Ascomycota), which contains other parasitic taxa such as the mycoparasite Escovopsis (Man et al. 2016), which specializes on the fungal cultivars of attine ants, and the entomopathogen Ophiocordyceps (Rogerson 1970). Russula and Lactarius hosts belong to the major mushroom-forming Class Agaricomycetes (Phylum Basidiomycota) and are both known to be ectomycorrhizal on a wide variety of tree species (Rochon et al. 2009).
The genus Hypomyces contains mycoparasites with varying apparent degrees of specialization. Within the boleticolous (bolete-parasitizing) species of Hypomyces there is diversity in extent of specialization, but many are restricted to a certain family or genus (Rogerson & Samuels 1989; Douhan & Rizzo 2003). Agaricicolous (agaric-parasitizing) Hypomyces also range in demonstrated specificity with the many genus-specific members, such as H. hyalinus on Amanita, contrasting with the narrow host preference of H. lithuanicus for Lactarius torminosis (Rogerson & Samuels 1994).
The transformation of the host sporocarp by H. lactifluorum is one of the more visually dramatic extended phenotypes caused by Hypomyces parasites, as lobster mushrooms are characterized by their bright orange color and twisted, deformed shape caused by the parasite mycelium covering the sporocarp (Laperriere et al. 2018). Aborted gill tissue of the host is replaced by the parasite (Spooner & Roberts 2005), for which there is no known anamorph (Rogerson & Samuels 1994). “Albino” infections of Russulaceae resembling lobster mushrooms have been identified as H. macrosporus, a separate species closely resembling H. lactifluorum but distinguished by color and chemistry (Rogerson & Samuels 1994). However, this classification of apparent white morphs of H. lactifluorum as a separate species has not been corroborated with molecular data.
The edibility of the lobster mushroom stands in stark contrast to the unpalatable taste of the uninfected Russula brevipes sporocarp. Laperriere et al. (2018) found that compared to uninfected Russula brevipes, the lobster mushroom sporocarp has a notable absence of terpenoids and a marked increase in lipids, characteristics that explain the increased gustatory appeal of the parasitized fruiting body. No other Hypomyces-infected sporocarp is known to be edible (Laperriere et al. 2018). Spore dispersal by vertebrate ingestion and subsequent defecation is well-established for truffle-forming fungi, and could be an explanation for the unusually palatable and conspicuous extended phenotype of H. lactifluorum infection.
Commercial lobster mushroom consumption is based on wild-harvesting operations, as cultivation has been unsuccessful (Berch et al. 2007). Better characterization of the parasitic association that creates the lobster mushroom complex could improve sustainability of wild-harvesting, as well as give insight into fungal diseases of cultivated mushrooms such as Agaricus bisporus.
References:
Berch, S. M., Ka, K.-H., Park, H., & Winder, R. (2007). Development and potential of the cultivated and wild-harvested mushroom industries in the Republic of Korea and British Columbia. Journal of Ecosystems and Management, 8(3). Retrieved from http://jem-online.org/forrex/index.php/jem/article/view/372
Douhan, G. W., & Rizzo, D. M. (2003). Host-parasite relationships among bolete infecting Hypomyces species. Mycological Research, 107 (11), 1342–1349. https://doi.org/10.1017/S0953756203008542
Laperriere, G., Desgagné-Penix, I., & Germain, H. (2018). DNA distribution pattern and metabolite profile of wild edible lobster mushroom (Hypomyces lactifluorum/Russula brevipes). Genome, 61(5), 329-336.
Rochon, C., Pare, D., Khasa, D. P., & Fortin, J. A. (2009). Ecology and management of the lobster mushroom in an eastern Canadian jack pine stand. Canadian journal of forest research, 39(11), 2080-2091.
Rogerson, C. T. (1970). The Hypocrealean Fungi (Ascomycetes, Hypocreales). Mycologia, 62(5), 865–910. https://doi.org/10.1080/00275514.1970.12019033
Rogerson, C. T., & Samuels, G. J. (1989). Boleticolous Species of Hypomyces. Mycologia, 81(3), 413–432. https://doi.org/10.2307/3760079
Rogerson, C. T., & Samuels, G. J. (1994). Agaricicolous Species of Hypomyces. Mycologia, 86(6), 839–866. https://doi.org/10.2307/3760597
Spooner B., & Roberts, P. (2010). Fungi. UK: HarperCollins.
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