(ORDO NEWS) — The fungus Entomophthora muscae has a survival strategy – it infects and “zombifies” female houseflies, and then sends out irresistible chemical signals that induce male houseflies to necrophilia.
By luring these male flies to mate with zombified females, the fungus can transfer to the male fly and, in theory, have a better chance of spreading further. The unfortunate male fly is then captured in the same way by E. muscae.
Crucial to this process is the release of sesquiterpenes, or chemical messages, which are synthesized in the female’s corpse and sent as a seductive signal. According to the results of experiments conducted by researchers, the longer the corpse was dead, the more attractive it seems to males.
“The chemical signals act like pheromones that bewitch the male flies and cause them to have an incredible desire to mate with the lifeless corpses of the females,” says evolutionary biologist Henrik H. de Fine Licht of the University of Copenhagen in Denmark.
As soon as E. muscae infects the female fly with its spores, it begins to reproduce. After about six days, he can control the insect’s behavior by sending it to the highest possible height (up a wall or a plant) before it dies. The fungal spores then fly out of the dead fly, hoping to land on another.
But by luring a male, E. muscae can ensure that it gets at least one more host, which again spreads its spores far and wide, a new study shows.
The team used various methods of chemical analysis and genetic sequencing to find out exactly what the fungus did, and also exposed male flies to females that were in different stages of a fungal infection or had died of other causes.
“Our observations show that this is a very clever strategy for the fungus,” says H. de Fine Licht. “He’s a real master of manipulation – and it’s incredibly exciting.”
Tests showed that female fly carcasses that had been dead for 3-8 hours attracted 15 percent of male flies, while carcasses that had been dead for 25-30 hours attracted 73 percent. The more time passed, the more chemical signals were released.
This is not the only time scientists have observed the use of sesquiterpenes to attract the attention of insects. Chemical signals are one of the most effective ways to manipulate these tiny creatures.
There is a lot of room for further research here, not least in developing effective fly repellents – flies can infect people with various diseases, and sesquiterpenes can be used to repel flies from certain places, such as where food is prepared.
“This is where the fungus Entomophthora muscae can be useful,” says H. de Fine Licht. “Perhaps we can use these same fungal scents as a biological pest control that attracts healthy males to fly traps instead of corpses.”
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