Zombie Toadstool attracts healthy male flies to mate with female corpses

Zombie Toadstool attracts healthy male flies to mate with female corpses

A male fly attempting to mate with a female corpse held in place by a dab of petroleum jelly. The fungus has outgrown the posterior segment of the body and is visible as large white spots from which spores are expelled. Credit: Filippo Castelucci

Entomophthora muscae is a common pathogenic fungus that survives by infecting common house flies with deadly spores. Now research shows that the fungus has a unique tactic to ensure its survival. The fungus “enchants” male houseflies and drives them into necrophilia with the fungus-infected corpses of dead females.

After infecting a female fly with its spores, the fungus spreads until its host was slowly consumed alive from the inside. After about six days, the fungus takes over the behavior of the female fly and forces her to the highest point, be it vegetation or a wall, where the fly then dies. When the fungus has killed the female zombie, it begins releasing chemical signals known as sesquiterpenes.

“The chemical signals act like pheromones, enchanting male flies and inducing an incredible urge to mate with inanimate female carcasses,” explains Henrik H. De Fine Licht, associate professor at the Institute of Environmental and Plant Sciences at the University of Copenhagen and one of the study authors.

When male flies mate with dead females, the fungal spores are spilled onto the males, who then suffer the same gruesome fate. In this way, Entomophthora muscae spreads its spores to new victims and ensures its survival.

That’s the conclusion of a new study conducted by researchers from the University of Copenhagen and the Swedish University of Agricultural Sciences in Alnarp.

“Our observations suggest that this is a very deliberate strategy for the fungus. He is a true master of manipulation – and that is incredibly fascinating,” says Henrik H. De Fine Licht.

Fly corpses become more attractive as the hours go by

By tracking fly behavior, the researchers were also able to show that dead female flies become more attractive over time.

Specifically, 73 percent of the male flies in the study mated with female fly carcasses that had died from the fungal infection between 25 and 30 hours earlier. Only 15 percent of males mated with female cadavers that had been dead for 3–8 hours.

“We see that the longer a female fly is dead, the more enticing she becomes to males. Because the number of fungal spores increases over time, which intensifies the seductive scents,” explains Henrik H. De Fine Licht.

In addition to the insight into the fascinating mechanisms of nature, the study provides new insights that may lead to effective fly repellents in the future. Henrik H. De Fine Licht adds:

“Flies are pretty unsanitary and can make people and animals sick by spreading E. coli and all the diseases they carry. Therefore, there is an incentive to limit housefly populations, for example in areas where food is produced. This is where the Entomophthora muscae fungus can come in handy. It might be possible for us to use the same mushroom scents as a biological pest control that lures healthy males to a flytrap instead of a corpse,” he concludes.

The study was published in The ISME Journal.

The research explained

  • The researchers used a variety of methods. These included chemical analysis of odorants emitted by the fungus and amplified in dead female flies, and studying the fungus’s genetics through RNA sequencing.
  • They also studied the sexual habits of male flies through behavioral experiments in which they were exposed to dead female flies that were at various stages of fungal infection, as well as females that had died from other causes. Here, research observations showed that male flies preferred to mate with fungus-infected females that had been dead for some time.

More about the zombie toadstool

  • Entomophthora muscae is a fungus that survives by controlling and infecting its host, namely flies.
  • The fungus secretes special enzymes that break down a fly’s body over the course of about seven days. The fungus can eject its infected spores at up to 10 meters per second, which is among nature’s fastest movements.

A fungus that uses chemicals to trick male flies into mating with infected dead females


More information:
Andreas Naundrup et al, Pathogenic fungus uses volatiles to lure male flies into lethal mating with infected female carcasses, The ISME Journal (2022). DOI: 10.1038/s41396-022-01284-x

Provided by the University of Copenhagen

Citation: Zombie fly fungus lures healthy male flies to mate with female corpses (2022 July 15) retrieved July 16, 2022 from https://phys.org/news/2022-07-zombie-fungus-lures-healthy- male.html

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