Bizarre Mind-Controlling Fungus Entices Male Flies to Mate With Dead Females

A deadly, mind-controlling fungus infects male flies by making them mate with infected female cadavers as a part of their "gruesome reproductive strategy."

Study finds that the pathogen releases some kind of irresistible substance resembling those produced by females when they're ready to mate, which behaviorally manipulates house flies for fatal mating so the fungus can consume a new host inside and out.

The pathogenic fungus (Entomophthora muscae) uses spores to poke from the dead, infected female flies which emits the scent, alluring healthy male house flies (Musca domestica) to mate with the corpse. The chemical compels the susceptible host to climb to an elevated surface so when they die with their wings outstretched, dispersing the fungal spores sprouting from their bodies would be distributed widely, in the advantage of the fungus.

Hitchhiking: Unknown Aspect of the Fungal Infection

"The fungus-emitted volatiles thus represent the evolution of an extended phenotypic trait that exploit male flies' willingness to mate and benefit the fungus by altering the behavioral phenotype of uninfected healthy male host flies," authors wrote in a study which have not been formally peer-reviewed.

According to lead author Andreas Naundrup Hansen, also a microbiology researcher at the University of Copenhagen, this aspect of the fungal infection has been previously unknown.

"We were very curious about this odd behavior, as it obviously seemed dangerous to the copulating male to have intimate contact with cadavers that were actively discharging infectious conidia (spores)," he said in an email.

Scientists found that the fungal spores hitchhike on a fly's exoskeleton, breaking through the tough outer cuticle, and "starts growing inside."

Male flies become more driven into mating with the dead corpses and it has something to do with the fungus. Later on, analysis of chemical signatures revealed that the compounds produced were "simply irresistible."

Mind-controlling pathogenic fungi

This trait is not exactly new to some pathogenic fungi, specifically those from genus Massospora that infuses mind-altering chemicals in cicadas. Another mind-bending example is the fungus Ophiocordyceps unilateralis which infects carpenter ants in the genus Camponotus.

In the study, researchers found two compounds in the aromas of the dead flies known as ethyl octanoate and a group of chemicals known as sesquiterpenes, known for their insect-luring abilities, emerging just a few hours after the females died.

According to Hansen, the behavior manipulation and sexual mimicry exhibited by male house fly hosts "could be especially important for the fungus because it's a species-specific pathogen that infects only house flies."

"When the access to new hosts is limited, it's crucial for the fungus to ensure transmission to new suitable hosts of the right species," he added.

This blended fungal compounds that is generated alter the level of natural host cuticular hydrocarbons in dead female flies, which then responded to by the healthy males.

"This is advantageous for the fungus as close proximity between host individuals leads to an increased probability of infection," authors noted.