Mycena crocata is a long-known species of fungus frequently reported from Europe and Japan, which was considered non-luminescent until now.
Heinzelmann et al. report evidence for bioluminescence in Mycena crocata and show that the genome of this species is fully equipped with the genes associated with fungal bioluminescence. Image credit: Heinzelmann et al., doi: 10.47371/mycosci.2024.03.001.
Mycena crocata is a species of the fungal genus Mycena known from Europe, Northern Africa, Asia and North America.
It predominantly occurs on leaf litter and woody debris of beech, and occasionally other hardwood trees like oaks, ashes, alders and birches.
Mycena crocata’s fruiting bodies appear in summer to autumn and are easy to identify.
They reach a height of 5-15 cm and have a slender stipe, which shows a characteristic color gradient ranging from bright orange-red at the base to a pale yellow or cream color at the top.
In addition, yellow-red or orange-red stains may be present on the whitish gills.
Most strikingly, however, Mycena crocata exudates a distinctive saffron-red sap when cut, which is also reflected in its common name saffrondrop bonnet mushroom, as well in the Latin species epithet crocata which means saffron-colored.
The evidence for bioluminescence in Mycena crocata was discovered by Zurich-based artists Heidy Baggenstos and Andreas Rudolf.
“We wanted to show that bioluminescent mushrooms are present in Swiss forests and that we do not have to travel far to find them,” Baggenstos said.
“One evening, while walking through the forest in Albisrieden, a neighborhood in Zurich, we observed some green light through the camera.”
“Sometimes the fungi’s bioluminescence is so weak it cannot be seen with the naked eye.”
Baggenstos, Rudolf and Dr. Renate Heinzelmann from the Swiss Federal Institute for Forest, Snow and Landscape Research further examined a large collection of Mycena crocata.
They investigated the bioluminescent properties of its fruiting bodies and mycelium using digital imaging and a photomultiplier.
In addition, they captured the bioluminescence spectrum emitted by the species and confirmed the presence of bioluminescence-related genes in its genome.
“The light measurements revealed that the fruiting body of Mycena crocata, apart from the stipe base, is non-luminous, while the mycelium showed the most bioluminescence,” they explained.
“As a result, the decaying wood Mycena crocata grows on can also emit a green glow when split open, lasting up to 4 hours, until the wood dries up.”
“When we grew pure mycelia cultures, under optimal conditions, these remained bioluminescent for up to 164 days.”
According to the authors, the ecological role of bioluminescence in fungi is still a mystery.
“In some fungal species with fruiting bodies with intense luminescence, bioluminescence attracts arthropods during night, which may promote spore dispersal,” they said.
“The spores of Mycena species are usually dispersed by wind and in species that do not have luminous fruiting bodies, such as Mycena crocata, bioluminescence likely plays a different, yet unknown role.”
“We conclude from our study that it is highly likely that there are other possibly well-known Mycena species whose bioluminescent properties have not yet been discovered,” they added.
“Consequently, existing studies on fungal bioluminescence may underestimate the frequency of bioluminescence in the mycenoid linage.”
“Further studies on the evolution of luminescence within the mycenoid linage are recommended to verify the luminescent properties of putative non-luminescent species in the absence of clear evidence for their lack of bioluminescence.”
A paper on the findings was published in the journal Mycoscience.
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Renate Heinzelmann et al. 2024. Is the bioluminescence in many Mycena species overlooked? – A case study from M. crocata in Switzerland. Mycoscience 65 (4): 173-179; doi: 10.47371/mycosci.2024.03.001