A fly goes about its day buzzing here, buzzing there, but then it starts acting weird. His movements slow down; his belly swells. White feathers are sprouting on his body.

Around sunset, there is a sudden burst of movement as the fly climbs or “peaks” to a high position, such as the top of a small plant or a stick, and extends its mouthparts. It sprays a sticky liquid that sticks tightly to its perch, then lifts its wings and dies.

Below, other unsuspecting flies are exposed to a shower of white spores emerging from the dead fly’s corpse. And the cycle starts all over again.

The white stuff that swallows these flies is a fungus called. Entomophthora muscae—Entomophthora means:destroyer of insects.” It is an obligate pathogen that is completely dependent on and infects the host. flies and turns them into “zombies” who do his will.

Discovered more than 160 years agoThe actions of the fungus are as mind-boggling as they are horrific. Scientists have long wondered: How can the fungus control the fly’s movements? brain? How does it “know” to do this at a certain time of day? What genes in his genome help him become a master manipulator?

Today, a series of experiments are underway to uncover the science behind this terrifying mind control.

fatal necrophilia

Henrik H. De Fine Licht, an evolutionary biologist at the University of Copenhagen, is one of the few people in the world working with “zombie” houseflies. Musca tame. Although initially drawn to the fungus E. muscle “Of course, I was also fascinated by the behavioral manipulation aspects and how that works,” he says, as he wants to study obligate pathogens.

These details are like fodder for a horror movie. Once the fungus infects the fly, it does not go directly to the vital organs, it first begins to consume fats and other nutrients, gradually starving the fly but ensuring its survival. However, when the non-vital organs it can eat are exhausted, it begins to control the fly’s behavior and thus ensures its continuity: By forcing the fly to seek a certain height and get stuck there, it allows its spores to spread over a wide area.

De Fine Licht was particularly intrigued by reports describing how the fungus was formed. female manipulates flies by making fly carcasses attractive to healthy males. Males fly to try to mate with infected cadavers and immediately become infected themselves. To investigate the nature of this deadly attraction, De Fine Licht and his team crushed infected and uninfected fly carcasses and examined the air surrounding the cadavers to extract and analyze the chemicals. In 2022, they reported: Fungi release volatile chemicals This attracts men.

De Fine Licht says it’s not entirely clear whether the volatiles attract male flies with the promise of sex or nutrition. A working hypothesis is that they may be attracted because they think it’s food. “But when they get closer, they start to smell the less volatile compounds in the cadaver, which then elicits sexual behavior,” he says.

Annette Jensen, an organismic biologist at the University of Copenhagen, also noticed something intriguing about how other insects react to the smell of dead flies. He and one of his students found that the earwig, an insect that feeds on other insects, was attracted to diseased fly cadavers. E. muscle and they prefer to feed on these rather than uninfected cadavers or cadavers infected with other types of fungi. The scientists came to their conclusion after conducting experiments in which earwigs were placed between two types of cadavers and were able to choose which one to move towards.

“It might have something to do with volatile substances Entomophthora muscaethis also attracts predators,” says Jensen, who wrote an overview fungi that are pathogenic to insects inside Annual Review of Entomology. “It’s probably super nutritious!”

Fruit flies join the list of victims

Most zombie fly studies have focused on houseflies, but Harvard University molecular biologist and zombiologist Carolyn Elya turned her research eye to fruit flies after serendipitously discovering some zombified flies in her backyard as a doctoral student at the University of California, Berkeley. He had used rotten fruit as bait to catch wild fruit flies for experiments, and was surprised to see some of the dead in that fairy-tale pose with their wings up, with white, feathery spores on their abdomens. He quickly extracted some DNA sequences from the spores and confirmed his hunch: These fruit flies, E. nov.

Elya continued to get infections Drosophila melanogaster It is a well-established laboratory model that researchers around the world have been working on for over a century. with this E. muscae-D. melanogaster systemeager to take advantage of the powerful DrosophilaExamine the fly brain to understand the genetic toolkit and how the fungus carries out its manipulation.

In a 2023 report, Elya and colleagues showed that the fungus may be secreting something into the fly’s “blood,” or hemolymph.which helps manipulate fly neurons. When he injected hemolymph from infected flies into uninfected ones, the latter began to behave as if they had been zombified.

Elya also discovered that circadian neurons, which help the fly follow its circadian rhythms, may play a role in time-sensitive altitude-seeking behavior. Silencing specific clusters of these neurons in the brain resulted in inhibition of peak activity in infected flies.

Elya also wants to understand this mind control from the mushroom’s point of view, and to this end he, De Fine Licht, and more recently others ranked huge E. musclegenome. Focusing on the strain that infects fruit flies, scientists reported finding genes similar to those carrying instructions for making a blue light sensor in a pattern called “white-collar 1.” Neurospora crassa. Inside N. crassa white collar 1 It plays a role in circadian rhythms, and so scientists suggest that this gene may play a role in directing the precise timing of infected flies’ peak-at-dusk behavior and subsequent death.

Scientists have also discovered many genes that may help the fungus take full advantage of the fly’s tissues and nutrients. These include specific genes encoding trehalase enzymes, which digest trehalose, the primary sugar in hemolymph; for proteins such as chitinases, which break down chitin in the fly’s exoskeleton; and for lipases that break down fats.

“That makes sense, right? Because these fungi are very specialized in using their hosts; “They grow inside the insects rather than by first killing them and then eating them, a strategy used by many generalist pathogens,” says Elya. “It’s important to be able to specifically target each tissue in the host.”

The search for more clues continues, with researchers moving beyond the static genome to examine RNA copies of genes that form when specific genes are active. In a research paper that has not yet been peer-reviewed, Sam Edwards, a postdoctoral researcher at Wageningen University in the Netherlands; De Fine Licht; and colleagues reported their analysis of RNA in housefly heads at different time points after a while E. muscleinfection. By finding which fly and fungus genes were active in the fly’s head, they hoped to gain insight into how the fungus manipulated the fly’s behavior.

The team detected the activity of a fungal gene called ecdysteroid UDP-glucosyltransferase, or “egt,” found in some zombified viruses. For example, these viruses E. muscle , they force their infected victims (in this case, caterpillars) to move to higher groundand, in a move more terrifying than their fungal counterparts, it causes the caterpillars to molt and release viral particles downward. Egt gene Plays a role in the caterpillar’s peak behavior caused by this virusSo researchers are now E. muscle is key to triggering peaking in infected flies.

In another change, both the preprint of De Fine Licht and A recent study at the University of California, Berkeley, co-authored by Elya find it E. muscle It may not work alone. Mushroom Looks like you’ve been infected with a virus It also parasitizes black flies and fruit flies. However, it is not yet known whether this virus helps the fungus control the fly.

Elya, De Fine Licht and others still want to know how the fungus begins its manipulation. One hypothesis is: E. muscle It secretes a chemical that activates neurons directly involved in the fly’s peaking behavior. But another hypothesis is that the all-consuming presence of the fungus and the resulting physiological changes in the fly trigger the fly’s own neurons to release chemicals to initiate the process.

De Fine Licht is keen for the zombie fly agaric system to be taught in schools to attract young science enthusiasts. He and Edwards recently issued these instructions: How to observe zombificating fungus in the laboratory. “It might encourage high school teachers and others to try it if they want,” says De Fine Licht.

Some of these involve collecting fly cadavers from the field and isolating the fungus from them.

“Or you could try to infect some healthy flies in the laboratory by putting them together with a cadaver,” says De Fine Licht. “This might be the most fun, right? “I’m trying to observe zombie behavior in a tiny box.”

Knowable MagazineIt is a work of journalism independent of the Annual Reviews.