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This spring, billions of cicadas will emerge after more than a decade underground, ready to climb trees and make noise while singing to attract mates. However, some of these insects will not achieve their reproductive goals; Instead, they will be controlled like zombies to spread a strange fungus that has taken over the cicadas’ bodies and behavior.
The details of the fungus’ attack on insects—destroying the insects’ genitals, replacing their abdomens with a cavity filled with fungal spores, driving the insects into hypersexual behavior to further spread the fungus, and turning cicadas into what some scientists call “salt shakers of death”—like they belong in a creature-feature horror movie They may appear. But Dr., an associate professor of ecology and evolutionary biology at the University of Connecticut in Hartford. When it comes to the Massospora cicadina mushroom, “reality is actually much stranger than science fiction,” John Cooley said.
Periodic cicadas lay their eggs on tree branches, and when these eggs hatch, the resulting baby cicadas, or nymphs, fall to the ground and dig in the soil. Depending on the species, they spend 13 or 17 years underground drinking sap from tree roots until it is time for almost adult cicadas to emerge. At some point, the insects are exposed to spores of the fungus Massospora cicadina. It is not clear to scientists whether this happens when the cicadas enter or emerge from the soil, or how this exposure occurs.
How does Massospora cicadina control cicadas?
The spores enter the cicadas’ bodies, and from that point on, the cicadas are at the mercy of the fungal parasite. A mass of fungal spores accumulates in the abdomen of each infected cicada. Eventually the cicada’s rear end (including its genitals) falls off. Dr., an associate professor of mycology and forest pathology at West Virginia University. In its place, a white fungal plug was revealed, “a mass of spores protruding from where the genitals and abdomen once were,” Matt Kasson said. “It looks like these cicadas have gum left in the chalk dust and stuck to their backside.”
Despite having chalky gumdrop spores instead of genitals, infected cicadas still attempt to mate with gusto. The fungus manipulates the cicadas’ behavior, causing what researchers, including Kasson, call hypersexualization. Infected males attempt to mate with females and also change their behavior to attract other males. Healthy female cicadas flap their wings to indicate that they are ready to mate. Both male and female cicadas infected with Massospora flap their wings to attract amorous males that will soon be infected.
But trying to mate is only part of how infected cicadas spread the fungus.
“Periodic cicadas have interlocking genitals. So guess what happens when they get separated from each other? Rest in peace. And then there’s a cicada wandering around with someone else’s genitals stuck to it,” Cooley said. “And now the infected cicada has broken open.”
When the chalky cork plug breaks apart, the infected and disembowelled cicada flies around, showering soft, brown spores. “We call them the salt shakers of death,” Kasson said. The spores dispersed by these flying salt shakers continue to infect the next generation of cicadas, which will emerge more than a decade later and start the cycle again.
Zombie cicadas stimulated by amphetamine?
Animals with fragmented bodies require a lot of movement and mating. Kasson and his colleagues have found a potential explanation for what keeps these cicadas going. “We found an amphetamine in these cork plugs, which provides a plausible explanation for why the behavioral change occurred,” Kasson said. After all, amphetamines are powerful stimulants in humans.
Cooley noted that although amphetamines stimulate the central nervous systems of vertebrates, insects like cicadas (all invertebrates) have different nervous systems, and it’s unclear whether these stimulants would affect them the same way.
“We’re faced with the problem of producing a strong psychoactive chemical, but the strong psychoactive chemical may not do anything to the insects,” Cooley said. He suggested that the fungus might have a different means of controlling cicadas’ behavior, and that the amphetamines it produces might instead serve to ward off vertebrate predators of cicadas (and therefore the fungi that live on cicadas) such as birds.
This spring’s periodic cicada emergence is notable because two different broods will emerge simultaneously in neighboring areas—17-year cicadas concentrated in northern Illinois and 13-year cicadas concentrated throughout much of the Midwest and Southeast. These two hatchlings have not emerged above ground at the same time since 1803; however, scientists expect the two offspring to have little geographical overlap.
Kasson said he hopes to examine infected insects from two different broods and see if there are genetic differences between M. cicadina infecting 17- and 13-year-old hatchlings.
Although cicadas are edible, Kasson said people hoping to sample the insects should be selective about which ones to eat. If you find adult cicadas near the end of their lives or already dead, “you don’t want to put them in your mouth,” Kasson said, regardless of whether they are infected with M. cicadina. If a person, dog or cat eats an infected cicada, it will not be affected by the amphetamines it contains; The dose is too small. And for “The Last of Us” fans, M. cicadina is only capable of infecting cicadas (and only the 13- and 17-year-old strains of those bugs), so humanity is probably safe from zombification.
Kasson said he understands people’s concerns about the impending cicada emergence, not to mention the strange fungal infection that up to 10% of them may develop. “This is a biological demonstration,” Kasson said. “And I think we should appreciate it as one of the natural wonders of the world.”
Kate Golembiewski He is a freelance science writer living in Chicago with a particular interest in zoology, thermodynamics, and death.
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