Drugged, Castrated, Eager to Mate: the Lives of Fungi-Infected Cicadas

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Science|Drugged, Castrated, Eager to Mate: the Lives of Fungi-Infected Cicadas


“This really has all the elements of a sci-fi horror story,” a mycologist said.

ImageDrugged, Castrated, Eager to Mate: the Lives of Fungi-Infected Cicadas
When cicadas are infected by a parasitic fungus, the insect’s innards get digested and their rear ends are replaced by a chalky white plug of spores.CreditCreditKasson et al.

Beneath the soil, cicadas wait — as long as 17 years — until the right temperature beckons them to the surface. At once, they emerge, like zombies rising from graves. They greet the sun, preparing to molt into adults in coming weeks and then fly off to mate.

Such is a cicada’s simple life — unless it’s been infected.

Massospora, a parasitic fungus, has lurked just below the surface, awaiting the cicada’s exit. When a nymph digs through infected soil, fungal spores cling to its body. As the cicada matures, massospora multiplies, digesting the insect’s insides, castrating it and replacing its rear end with a chalky white plug of spores.

The cicada buzzes on, seemingly unaware it’s a mushroom’s moving minion. It flies, attempting to mate with unusual vigor. Some males even mimic females to attract and spread their spores to male partners — the more infected, the better. And as their hijacked bodies copulate, spores sprinkle to the earth and massospora spreads.

“This really has all the elements of a sci-fi horror story,” Matthew Kasson, a mycologist at West Virginia University, said. “How does an organism function even though two-thirds of their body is no longer theirs?”

Perhaps, he thinks, the fungus dopes it with psychoactive drugs.

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As reported last year in a paper that had not yet been through peer review and in the Atlantic, Dr. Kasson and colleagues discovered the infected cicadas’ plugs were laced with an amphetamine called cathinone, found only in the khat plant of the Horn of Africa and the Arabian Peninsula, and psilocybin, the hallucinogen that makes magic mushrooms magic.

At the time, his team assumed massospora synthesized these drugs on its own, following the same recipes in khat and magic mushrooms. But a follow-up genomic analysis, published recently in Fungal Ecology, revealed massospora didn’t have the right ingredients. Its drug lab had evolved independently. It also shows that for prospectors seeking pharmaceutical advances in nature, there are more drugs to be found in unexpected places.

We think of most fungi as having fruiting bodies that rise from the soil like umbrellas. But massospora has none. To transport its spores, it uses the cicada’s living body, which spreads the fungus as it mates, like an STD.

But how does the fungus get the cicada to ignore the damage to its body and carry on mating?

Dr. Kasson and his team collected cicadas and measured the mass of their spore plugs, comparing it with known chemicals.

He was shocked to find psilocybin and cathinone, both schedule 1 drugs, and even informed the federal Drug Enforcement Administration, which allowed the team to continue.

These drugs, used recreationally as mind-alterers or stimulants, are also appetite suppressants. Psilocybin eases depression and anxiety in cancer patients, and cathinone in ADHD medications improves concentration. Dr. Kasson suspected they might act similarly on cicadas.

It turned out that infected annual cicadas, which rise each year, were under the influence of psilocybin, while infected periodical cicadas, which emerge after more than a decade, were drugged with cathinone.

And the cicadas infected when emerging from their dirt naps had significantly higher amounts of narcotics in their plugs than the less-active cicadas they infected as adults while copulating. The drug-fueled focus on mating could maximize the critical spore dispersal of those cicadas infected as nymphs.

The team had found the drugs. But they wondered what made them.

When they sequenced the genomes of massospora fungi species that infect cicadas, they expected to find the genes used by magic mushrooms or khat to produce the narcotic substances. But those genes were missing. One possible explanation is that the fungus and cicada, maybe including the microbes living in its gut, co-evolved a unique interaction to produce these substances.

But what would the cicada get out of it?

Dr. Kasson can only speculate. Maybe drugs make cicadas less desirable to predators. Maybe they make cicadas fearless. “Maybe the cicadas just want to feel numb,” he said.

Earlier reporting on parasites and fungi