- A parasitic fungus called Entomophthora muscae manipulates the behavior of the housefly
- The ferocious fungus kills insects from the inside out once it infects house flies
- Danish experts have shown that it releases a mixture of compounds to entice another prey
A creepy species of parasitic fungus turns flies into ‘zombie’ necrophiles by emitting a powerful chemical aphrodisiac, a new study shows.
Researchers in Denmark have found that the fungal species, Entomophthora muscae, releases a potent mixture of fungal compounds once lethally infects a female housefly.
Healthy male flies respond to a tangled mix of chemical compounds by mating with dead zombie females, ensuring the spread of the fungus.
When E. musca infects house flies, it enters their skin, produces spores throughout their bodies, digests their guts, and kills them in five to seven days.
A fly killed by the Entomophthora musky fungus, which climbs to a high point and spreads its wings to expel spores from its abdomen
How do E. muscae use houseflies?
Entomophthora muscae infects house flies by penetrating their skin.
It grows in the body of the flies, digests their guts and kills them in five to seven days.
The fungus can also hijack the brains of insects – forcing them to descend to a surface and crawl upwards to give the parasite a better shot at spreading.
On a fly corpse, the fungus develops a series of tiny spore cannons to infect other flies that are nearby.
The fungus infects both male and female house flies, but the new study, led by researchers at the University of Copenhagen, focused on the effect of female infection on attracting male flies.
The scientists gave male flies the option to mate with infected and non-infected dead females.
‘Healthy males are attracted to carcasses killed by fungus’ [dead bodies] and engage in courtship and mating efforts, which significantly increase infection of new host individuals and thereby ensure transmission of the fungal pathogen,’ the authors state.
‘e. muscae induces changes in volatile chemistry that attract house flies by altering cuticular fly hydrocarbon levels and producing a number of unusual volatile compounds.’
‘Unusual volatile compounds’ include a class of chemicals known as sesquiterpenes, not previously associated with house flies.
Sesquiterpenes have already been found to be attractive in many other insects, including the Asian bee and bumblebee, the researchers report.
Previous studies have already detailed the ruthless process of infection of E. muscae. Its genus name, Entomophthora, translates to ‘destroyer of insects’ – and that’s no surprise.
Once infected, spores called conidia are produced from the fly – a process known as sporulation.
E. muscae causes flies to climb to a high point and spread their wings like a puppet on a string, to eventually spew spores from their swollen abdomen.
The fungus invades the fruit fly’s nervous system and swallows the brain and muscles before forcing it to climb a deadly climb, known as ‘peak disease’.
Entomophthora muscae turns its prey into a zombie. Once infected, E. muscae causes flies to climb to a high point and spread their wings like a puppet on a string to expel spores from their swollen abdomen
When the fly dies, the fungus develops a series of microscopic-sized stalks on the corpse, each a spore with a pressurized cannon of liquid that can be ejected.
Unlucky male flies are attracted to the corpses of ‘zombie’ female flies – and when they accidentally trigger the cannons, they become coated in a spray of infectious spores.
This ensures that the fungal spores are spread as widely as possible so that the grueling process is repeated on another fly.
Overall, the E. muscai infection process itself does not differ between male and female houseflies.
Now, researchers show that it is not only the changed shape and form of the dead fly that attract unsuspecting males, but the powerful compounds, which act as a love potion.
In a laboratory setting, researchers offered male flies the choice between mating with ‘early killed’ dead females (equivalent to the early sporulation stage) and ‘late killed’ dead females (equivalent to the late sporulation stage) .
They observed a significant increase in mating attempts when the dead female was in the final stages of sporulation – a clever ploy to maximize the chances of further infection.
On the corpse of a fly, the fungus develops a series of tiny spore cannons to infect other flies that are nearby.
The team explains, ‘Close physical contact in the late stage of infection increases the likelihood of fungal transmission because there are more infectious conidia than in the early stage where the conidiophores are just maturing.
The results also showed that 73 percent of male flies were infected after exposure to late-killed flies, while 15 percent of males were exposed to early-killed flies.
Genome analysis also revealed that there was high expression of several key enzymes known to trigger the production of various compounds, including ‘long-chained alcohols and esters’, of late-killing.
After infecting the males as well, the researchers found several fungus-produced volatile compounds that were similar between the infected male and female carcasses.
However, there were differences in the amounts of some of these compounds between males and females.
Study leader Andreas Naundrup told MailOnline: ‘Certain compounds that are associated with female sex-pheromone function that can stimulate male sexual behavior were increased in infected female cadavers.
The study focused on females because males are believed to be more likely to come into contact with the spores through sexual contact with an infected female.
‘Therefore in addition to being attracted to both male and female conidia, males would also have a sexual attraction to being prone to conidia…