A new study shows that a creepy parasitic fungus transforms necrophiles into ‘zombies’ by emitting a powerful chemical.
Researchers in Denmark discovered that the Entomophthora species of fungus, Entomophthora mucae, releases a powerful mix of fungal compounds after it infects a female housefly.
Healthy male houseflies respond to the interesting mix of chemical compounds by mating the dead zombie female, which ensures the spread of the fungus.
E. muscae infects houseflies. It penetrates their skin, spreads spores throughout their bodies, and then kills them in five to 7 days.
A fly killed by the killed by Entomophthora muscae fungus, which ascend to a high point and spread their wings to spew spores from their abdomen
The fungus infects both male and female houseflies, but the new study, led by researchers at the University of Copenhagen, looked at the effect of female infection to attract male flies.
The scientists gave male flies the option to mate with infected and non-infected dead females.
“Healthy males are attracted by fungus-killed corpsvers [dead bodies]The authors state that courtship and mating efforts can increase the risk of fungal infection in new hosts and thereby increase the transmission of the pathogen.
“Infection with E. Muscae causes changes in volatile chemistry that attract houseflies by altering the levels cuticular fly hydrocarbons as well as by producing unusual volatile compounds.
Sesquiterpenes are a class of chemicals that have never been associated with house flies.
Sesquiterpenes have already been found to be attractive in several other insects, the researchers report, including the Asian honey bee and bumblebees.
Previous studies have shown that E..muscae is capable of infecting a host of insects with a brutal and relentless manner. Its genus name, Entomophthora translates to ‘destroyer of insects’ – and it’s no surprise why.
Once infected, spores called conidia are produced from the fly – a process called sporulation.
E. muscae causes flies t to rise to a high point, spread their wings like marionettes on a string, and eventually to spew the spores out of their swollen abdomen.
The fungus infects the fruit fly’s nervous systems and forces it to climb the fatal climb, also known as “summit disease”, before eventually devouring its brain and muscles.
Entomophthora.muscae makes its victim a living, breathing zombie. E. muscae infects flies and causes them to rise to a high point, spread their wings like marionettes on a string, and then spew spores out of their swollen abdomens.
The fungi forms a series of micro-sized stalks from the corpse of the fly after it is dead. Each one is a pressure cannon filled with liquid and a spore that can then be ejected.
Unfortunate male flies are attracted to ‘zombie’ female fly corpses – and when they accidentally trigger the cannons, they end up coated in a spray of infectious spores.
This ensures that the fungalspores are spread as widely as possible, so that the horrifying process can occur again.
Researchers now show that it’s not just the altered appearance and size of the dead fly that attracts males, but also the potent compounds that act as a kind of love potion.
The fungi that lives on the fly corpse creates a number of tiny spore guns to infect any other flies near it.
Researchers gave male flies the option of mating with ‘early-killed’ dead females (equivalents to an early sporulation phase) or ‘late-killed’ dead females in a laboratory setting.
They found a significant increase in mating attempts when the dead female was in a late stage of sporulation – a crafty trick to maximise chances of further infection.
The team explained that close contact in the late stage of infection increases the likelihood of fungal transmission. This happens because there is more infectious conidia than at the beginning stage, where conidiophores are still maturing.
Results also showed that 73 per cent of male flies had become infected after exposure to the late killed flies, compared to 15 per cent of males exposed to early killed flies.
Genome analysis also revealed that late-killed patients had higher levels of key enzymes that trigger the production and release of many compounds, including ‘long chained alcohols’ and ‘esters’.
It is possible that the release of chemicals during infection and the initial volatile attraction of fungus’s next victim could be related to food.
The team says that the negative effects on mating suggest that male houseflies feed off the conidia around them rather than being stimulated by mate-making.
This research is described as a preprint and will be peer-reviewed on bioRxiv.