Magic mushrooms have been providing transformative experiences for thousands of years. Researchers suggest that fungi developed hallucinogenic compounds like psilocybin as a biological defense against insect herbivores.

Psilocybin is the main psychoactive component in magic mushrooms, present in various species found on every continent except Antarctica. Historically, these mushrooms have been utilized by shamans in traditional cultures. Recent studies are investigating psilocybin’s potential as a therapy for mental health disorders, including depression and PTSD.

This psychedelic compound primarily interacts with serotonin receptors in the human brain. However, the evolutionary reasons that lead fungi to produce compounds similar to animal neurotransmitters remain unclear. As John Ellis from the University of Plymouth points out, “There’s speculation that psilocybin serves a protective role against invertebrate fungivores, but these ideas need further exploration.”

To explore the effects of psilocybin on insects, Ellis and his team fed fruit fly (Drosophila melanogaster) larvae with dried magic mushrooms (Cylocyber cubensis). The researchers monitored the larvae’s survival rates, growth rates, and adult size and development.

Additionally, the team created liquid extracts from the mushrooms, combined them with a minimal amount of sucrose, and observed the larvae’s movements after exposure. “It resembled immersing them in a sweet magic mushroom solution,” says team member Kirsty Matthews Nicholas.

“By quantifying how rapidly the insects crawled, the distances traveled, and their overall movement coordination, we assessed the immediate impacts on their nervous systems,” Nicholas explains.

Results showed that larvae exposed to a magic mushroom diet exhibited significantly reduced survival rates. At lower doses, more than half of the larvae did not survive to adulthood. At higher doses, survival rates dropped to just about 25%.

“Among the flies that did reach adulthood, the consequences were evident. Adult flies were smaller, had shortened bodies, and asymmetrical wings – all indicators of developmental stress,” Nicholas reported. “They crawled shorter distances, moved less overall, and displayed erratic movement patterns, leading to slower and less coordinated motion.”

However, it is unlikely that insects experience psychedelia as humans do. “Our findings imply that compounds like psilocybin disrupt essential insect physiology and behavior in ways that could be detrimental rather than psychedelic,” she notes.

The research team also collected and analyzed seven mushroom species from Dartmoor, UK, and found that the DNA of invertebrates present varied according to the psilocybin-producing fungi—indicating a specific interaction pattern between these fungi and their insect hosts.

Unexpected outcomes highlighted the complexity of psilocybin’s ecological role. For instance, fruit flies with decreased serotonin receptor counts, typically impacted by psilocybin, were found to be more affected. Furthermore, the flies also showed adverse reactions to extracts from control mushroom species devoid of psilocybin.

Fabrizio Alberti from the University of Warwick indicates that their findings demonstrate that non-psilocybin mushrooms also generate other metabolites that harm insects’ speed and survival.

“Ongoing research utilizing pure psilocybin on insects will be essential to clarify its ecological significance and explore whether this psychedelic compound evolved as an insect deterrent,” Alberti emphasizes.

This study raises critical challenges in understanding the evolutionary implications of psilocybin-producing fungi. Bernhard Rupp from the University of Innsbruck, Austria, suggests, “Mushrooms producing psilocybin and similar compounds may have significant evolutionary advantages, such as deterring consumption by insects and snails.”

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