As we await the “cicada apocalypse” this spring and summer, when trillions will emerge in the South and Midwest United States, some of the bugs may be facing a predicament that sounds like science fiction. A sexually transmitted fungal pathogen, exclusive to these periodical insects, called Massospora cicadina can control them as a “puppeteer”. It causes infected cicadas to act hypersexually and infect other insects before eventually dying.
Bellies pierced by fungus
Massospora cicadina it can also affect both periodical cicada hatchlings that will emerge in the coming weeks and months. Brood XIII – the Northern Illinois Brood – will make its first appearance since 2007 and spans parts of Indiana, Wisconsin, Iowa and northern Illinois. Some of Brood XIX – the Great Southern Brood – will overlap with Brood XIII. The Great Southern Brood last appeared in 2011 and is found primarily in Arkansas, Missouri, Tennessee, Alabama, George, North Carolina, South Carolina, and southern Illinois.
When they emerge, the cicadas molt into adults. Within a week to 10 days, this fungus opens up the back of their abdomen. Scientists are still not sure when in their life cycle cicadas can initially become infected with Massospora cicadinabut the prevailing hypothesis is that they are infected on their way up from the earth.
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According to West Virginia University mycologist Matt Casson, infected cicadas look like they have “a drop of gum that got wet and fell into chalk dust” on them.
“If you look at a fungus-infected cicada, you’ll see that basically the back side of the body has been replaced by this chalky white fungal plug,” Casson says PopSci. “Now, if you or I had our bellies pierced by a fungus, or a third of our body replaced by some parasite, we probably wouldn’t feel well. We probably won’t try to mate. We would just feel awful, lay down and die.
However, the infected cicadas continue to fly around as if nothing is wrong with them, even though their genitalia have been engulfed by fungus. They can do this because the fungus has sent them into a period of extended wakefulness – a time of increased endurance.
“A hypothesis for this prolonged wakefulness is that the mushroom produces an amphetamine called a cathinone,” Casson says. Kasson says it’s similar to one of the synthetic stimulants commonly found in “illegal bath salts that have been banned because of the aggressiveness that [they] would cause.”
Silent Fungal “Puppeteer”
This causes cicadas to act hypersexually, where males will continue to try unsuccessfully to mate with females and also mimic female behavior to attract other males to mate with them. This then doubles the number of cicadas that will eventually become infected and can therefore be considered sexually transmitted.
Massospora cicadina’s the ability to keep the host alive long enough to maximize the number of infected cicadas makes it a biotroph. It doesn’t work like Ophiocordyceps unilateralis a fungus that takes over ants and makes them act like zombies or the fictional mushrooms from the TV show and video game The last of us which pops up in dramatic fashion.
[Related: The Cicadapocalypse is nigh. 7 cicada facts to know before it hits.]
“It’s a trick of the fungus and it’s like a puppeteer,” Casson says. “He’s pulling strings to maximize his own survival.”
Infection rates can be as high as 20 percent of cicadas if environmental conditions are perfect, but some older studies have shown that it affects about five percent of cicadas in a given brood.
Optimizing its genome
Massospora cicadina was first discovered in the mid to late 1800s. Because periodic cicadas only appear every 13 or 17 years, studying this fungus is difficult. It also can’t be cultured on a petri dish, so mycologists have a limited window to study them, and they’re still not sure where it came from.
In 2016, Brood V appeared near Kasson’s office in West Virginia, and some of his students suggested looking for signs of this fungus. They were able to sequence parts of his genome to see what made him special. What they found was the largest genome ever sequenced for a fungus at about 1.5 billion bases.
“It’s about 20 times the size of the average human genome, and it’s mostly filled with these repetitive sequences called transposable elements,” Casson says.
They point out that Massospora cicadina has essentially spent millions of years optimizing its genome right along with the cicada. The fungus and the insect seem to have co-evolved so that it can manipulate its host in a specific way, not to kill it, but to ensure its own survival. According to Kasson, their data on this coevolution is not yet published, but it shows some interesting evolutionary dynamics.
“What we’re seeing is a pattern where basically the cicadas have evolved in parallel with all the fungi,” Casson says.
Massospora cicadina it is not transmissible to humans, but you would be wise to avoid eating cicadas that have white, chalky plugs on their abdomens. Infected bugs won’t come with any cheer or buzz, but they do have several toxins that can be dangerous if eaten.
“We found 1,000 other chemical compounds, some of which are known mycotoxins,” Casson says. “So proceed with caution if you’re thinking of consuming one of these cicada mushrooms.”
