A parasitic fungus called Entomophthora muscae manipulates the behavior of common house flies ( Musca domestica ) by releasing a chemical mixture that causes males to turn into necrophilia-addicted zombie insects.
A zombie potion of lust
The need to reproduce is an irrepressible urge in nature. This has been witnessed by a new study carried out by scientists from the University of Copenhagen (Denmark), which has discovered a fungus that modifies the behavior of the insect to increase its own propagation potential, altering the chemical signals of another corpse – another victim of the fungus – to attract the attention of males . Involuntary necrophilia leaves the male vulnerable to infection while mating with already dead insects, allowing further spread of the fungus.
The researchers analyzed the pathogenic fungus Entomophthora muscae and its influence on the house fly, noting that by exposing infected and uninfected dead females to male flies to see if they would attempt to mate with either, the chances that the male would mate with both dead females they increased if one of the dead flies was in the last stages of sporulation (swollen corpses, literally full of spores) of the infection.
“This is advantageous for the fungus , since the proximity between the hosts leads to a higher probability of infection,” the authors explain.
The sporulating females, the most attractive
To confirm the observation, the researchers incubated the male flies for 10 days. Almost 75% of males exposed to late-stage sporulating females became infected, compared with 15% of males who attempted to intercourse sexually with early-stage sporulation carcasses. They also measured the responses of the male housefly to volatile compounds that surround live flies, uninfected carcasses, and sporulating carcasses. Dead spore-laden females were still more attractive to male flies.
“Healthy males are attracted to corpses as a result of the action of fungi and are involved in courtship and mating attempts , which significantly increases the infection of new host individuals and, therefore, ensures the transmission of the fungal pathogen” say the authors. “Infection with E. muscae induces changes in volatile chemistry that attract house flies by altering the fly’s cuticular hydrocarbon levels and by producing several unusual volatile compounds.”
These compounds include a class of chemicals called sesquiterpenes, which have not previously been associated with house flies (but have been associated with Asian honey bees and bumblebees, for example).
The fungus invades the fly’s nervous system and forces it to ascend to the highest possible point, something known as ‘summit disease’, spewing the spores with its hugely swollen abdomen, before the malevolent fungus devours the brain and the muscles of the victim.
Referencia: A pathogenic fungus uses volatiles to entice male flies into fatal matings with infected female cadavers
Andreas Naundrup, Björn Bohman, Charles A. Kwadha, Annette B. Jensen, Paul G. Becher, Henrik H. De Fine Licht
doi: https://doi.org/10.1101/2021.10.21.465334
This article is a preprint and has not been certified by peer review yet.
