Fig. Male house fly mating attempts towards E. muscae cadavers. A healthy male house fly trying to mate with E.muscae sporulating. White bands of fungal growth (conidiophores containing conidia) can be seen extending from the abdomens of the deceased female. The conidia that are actively being released cover large areas of the female cadaver's wings and body and create a halo around it (Photo by Filippo Castelucci). b. Male mating attempts toward uninfected freeze-killed (Em), or infected (+Em), E. muscae killed cadavers in the early (3-8 hours after death) and late (26-28 hours after death) sporulation stages. (n = 15 per treatment). c. Total mating attempts of a male towards any cadaver, when presented with a choice among two female cadavers. One was uninfected (-Em), Em), and one was infected or uninfected in the early sporulation stages (-Em and +Em). (n = 9-19 per therapy). Credit: DOI: 10.1101/2021.10.21.465334
Researchers from the University of Copenhagen, the Swedish University of Agricultural Sciences and the University of Copenhagen reported that a certain fungus uses chemicals in order to trick male flies into mating with infected females. The researchers have published a paper detailing their findings on the bioXiv preprint site.
Research has shown that certain types of fungus may infect insect victims with what is now known as summit disease. In this case, the victim's nervous system becomes infected and they climb to the highest point. Once the victim is infected, their wings spread out wide and they begin to spew spores. Researchers have discovered a fungus which can cause summit disease by making female victims emit chemicals that attract males.
Researchers discovered that the fungus Entomophthora Muscae could infect other insects with summit disease. Female victims are infected by airborne spores that penetrate their skin. They soon infiltrate her entire body, including her brain and nervous system. The spores produce chemicals that incite the female to climb until she reaches the top, like a leaf on the tree. She then opens her wings and ends up dead. The spore-filled cannons of fungus cover her body while she is still alive. A male comes by at some point and touches her body. The cannons then light up, infecting all nearby people with the spores.
Researchers captured both infected and uninfected flies in their laboratory. Males had the option of mating with an infected or uninfected female. More often than not, they chose the infected one. The fungus may have been making the female infected more attractive than the male, even though she was already dead. The researchers discovered unusual volatile compounds in the females. These chemicals, called sesquiterpenes were not usually associated with houseflies, but they were found to attract many kinds of insects including houseflies.
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More information: Andreas Naundrup and colleagues, Pathogenic fungus uses volatiles for male flies to incite them into fatal matings, bioRxiv (2021). Andreas Naundrup and colleagues, Pathogenic fungus uses volatiles in order to lure male flies into fatal matings, (2021). DOI: 10.1101/2021.10.21.465334
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