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Nature is terrifying: Zombie cicadas turning other cicadas into zombies

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Aug 3, 2020, 10:11 AM EDT

Zombified bugs taken over by a killer parasitic fungus is the stuff of retro B-horror at its finest — except it isn’t. Some things in nature are horror movies in themselves. Massospora is the star. It literally plays mind games with unknowing cicadas, forcing them to exhibit mating behavior just so they infect other cicadas and keep spreading fungal spores like a case of the worst STD ever.

Researchers from West Virginia University have now found out how the zombie fungus manipulates hordes of undead cicadas by injecting them with hallucinogens, all while eating them alive. It might not be tetrodotoxin, but psilocybin (the same stuff found in magic mushrooms) can make the brain do weird things. This is starting to sound like the spawn of Matango and Mimic.

“Active host transmission (AHT) is a form of biological puppetry in which the pathogen manipulates the behavior of its powerless host,” said Brian Lovett, who co-authored a study recently published in PLOS Pathogens. “AHT requires a living host and host behavior that facilitates pathogen transmission, thereby increasing pathogen fitness at the expense of host fitness.”

So maybe active host transmission isn’t a case of reviving dead things, but it is a living death. Rabies (which has been more sensationalized in horror movies) behaves in a similar way. Victims become hydrophobic, and their fear of swallowing only helps the virus multiply around their mouths — which is what makes them more likely to bite. By the way, zombie raccoons are a thing.

Massospora is thought to either be contracted by cicada nymphs as they crawl out of the ground or hang out in their bodies as they chew on tree roots underground. When the brood emerges, it gets in the males’ heads and abdomens. Infected male cicadas will exhibit wing-flicking behavior that is supposed to be an exclusively female behavior. Other males will see this and come running.

Unfortunately, because cicadas are not dimorphic, the attracted cicadas have no idea they’re being tricked by zombies that are about to zombify them. They also become more desperate later during the mating period. That makes them even more likely to get infected, and when they do, they are probably too busy flicking their wings to notice that the fungus is eating their entire abdomen from the inside. The infection isn’t always conspicuous. While zombies on TV and in the movies appear corpselike, cicadas in the early stages of Massospora infection may appear healthy while their guts are being devoured. They need to be kept alive long enough for the fungus to spread even if their innards literally fall out in the process.

“AHT parasites also modify host behaviors so that parasite reproductive structures appear when hosts are manipulated to increase their interactions with uninfected potential hosts. This synchronization could either exploit natural host behaviors or induce behaviors that increase the frequency of interaction between host insects,” Lovett said.

There is still some mystery around how microscopic monsters like this evolved. Studying them is a challenge because the fungi cannot be cultivated without the host, and because juvenile cicadas spend 13 or 17 years underground, depending on the species, providing a host is often impossible. What the WVU scientists can infer is that AHT fungi has somehow been able to purposely create its lifestyle, both in how it disfigures a particular insect and produces at least two types of spores. How this evolution occurred is still unknown. It is thought to have resulted in their enormous genomes, which contain the same DNA on repeat, which probably means Massospora are now hardwired to be cicada parasites.

At least cicadas aren’t in any real danger. They multiply so fast that the healthy ones far outnumber the zombies, so an insect apocalypse isn’t likely to happen because of mass zombification. At least not anytime soon.

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