Study

Psychoactive plant- and mushroom-associated alkaloids from two behavior modifying cicada pathogens

Boyce, Greg R.; Gluck-Thaler, Emile; Slot, Jason C.; Stajich, Jason E.; Davis, William J.; Kasson, Matt T.

Fungal Ecology, 2019

Peer-reviewedcomparative studylaboratory

What they did

Infected cicadas were analysed by mass spectrometry for small-molecule content, and the fungal genomes examined for the biosynthetic pathways that would be required to produce any compounds detected.

Studied in: Massospora cicadina, Massospora platypediae, Magicicada
Sample size: chemical analysis of infected cicadas across two Massospora species

Cathinone, an amphetamine, was detected in periodical cicadas infected with Massospora cicadina. Psilocybin was detected in banger-wing cicadas infected with a different Massospora species. Neither compound had previously been reported from these lineages, and in the case of psilocybin the fungus is unrelated to the mushrooms that normally produce it. The biosynthetic route in Massospora was not identified.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Two Massospora species independently produce or accumulate psychoactive alkaloids, which may contribute to the behavioural changes seen in infected cicadas.

How NatureHQ reads it

This is where the "zombie fungus drugs cicadas" story comes from, and the chemistry is real and strange — an amphetamine in one, psilocybin in another, in a fungal lineage with no known relationship to the organisms that usually make either. What has not been shown is any of the connecting steps. Nobody has established the concentrations reaching cicada tissue, nor that these compounds affect insect behaviour at those concentrations, nor that the observed behavioural changes are caused by them rather than by the extensive physical destruction of the animal. Insect and vertebrate nervous systems also differ in the receptors these compounds act on. The authors present a hypothesis and label it as one; the reporting converted it into a mechanism.

Limitations

Detection establishes presence, not concentration at a site of action or any behavioural effect.
No causal experiment links either compound to the observed behaviour.
The biosynthetic origin was not resolved, so acquisition from the host or environment is not excluded.
Small numbers of infected individuals, collected opportunistically.