zombie-fungus

A stalk of the newfound fungus species Ophiocordyceps camponoti-balzani, grows out of a “zombie” ant’s head in a Brazilian rain forest.

 Originally thought to be a single species, called Ophiocordyceps unilateralis, the fungus is actually four distinct species—all of which can “mind control” ants—scientists announced last week. (pics)

 

The fungus species can infect an ant, take over its brain, and then kill the insect once it moves to a location ideal for the fungi to grow and spread their spores.

All four known fungi species live in Brazil’s Atlantic rain forest, which is rapidly changing due to climate change and deforestation, said study leader David Hughes, an entomologist at Penn State University.

Hughes and colleagues made the discovery after noticing a wide diversity of fungal growths emerging from ant victims, according to the March 2 study in the journal PLoS ONE.

“It is tempting to speculate that each species of fungus has its own ant species that it is best adapted to attack,” Hughes said.

“This potentially means thousands of zombie fungi in tropical forests across the globe await discovery,” he said. “We need to ramp up sampling—especially given the perilous state of the environment.”

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Healthy Camponotus rufipes ants scamper across a Brazilian forest floor.

The four newly identified “zombie” fungi species use different techniques to spread after infecting an ant, the researchers found.

Some of the fungi species create thin “infection pegs” that stick out from a victim’s body and infect passing ants, Hughes said.

Other fungus species develop explosive spores on infected ants’ bodies. When other ants come near the cadavers, the shooting spores can hit the unwitting passersby, turning them too into zombie ants.

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Lodged in a zombie ant’s brain, the fungi species “direct” the dying ants to anchor themselves to leaves or other stable places, as pictured above—providing a stable “nursery” for the fungus.

For instance, as the Ophiocordyceps camponoti-balzani fungus is about to kill the ant, the insect bites down hard into whatever substance it’s standing on.

This attachment is so strong that a dead zombie ant can remain stationary even when hanging upside down, the scientists say.

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A white fungus stalk (left) of the Ophiocordyceps camponoti-rufipedis species begins to poke through the head of a zombie ant two days after death. Also noticeable are faint, white, slightly fuzzy fungal growths on the ant’s joints.

Once the insect dies, the fungus rapidly spreads through the body. During the first couple days, though, very little evidence of the fungus is visible from the outside.

During later stages of Ophiocordyceps camponoti-rufipedis infection, the fungus rapidly consumes the nutrients inside a zombie ant and begins to colonize the outside of the ant’s body.

The fungus stalk growing from the back of the head also becomes longer and more noticeable.

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The mature fungus stalk, shown growing from a zombie ant’s head during the final stage of infection, differs among fungi species.

For instance, Ophiocordyceps camponoti-rufipedis creates just a single stalk (pictured), while Ophiocordyceps camponoti-balzani forms a forked stalk.

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Ants aren’t the only zombie-fungi hosts—other insects also fall prey to fungus. Above, a wasp is infected by a Cordyceps fungus species that hasn’t yet been named or formally documented.

Fungi of the Cordyceps genus are the products of a tightly evolved arms race between hosts and parasites, study author Hughes noted.

That means the fungi are often locked into one type of host—a specialization that might spell doom for fungi species as host species die out.

Unlike ants, many insect species that fall victim to zombie fungi are very difficult to identify after the fungus has spread around their bodies the scientists noted.

Overall, fungi help keep nature working smoothly, Hughes added.

“They may be less cuddly than pandas … but for the overall health of the planet, fungi are inestimably more important.”

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Crickets too can fall prey to zombie fungi (as pictured), though little is known about the fungus species that brought this insect to its horrific end.  Hughes plans to remedy that—and expects to find many more zombie fungus species in the forests of Brazil.  “This is only the tip,” he said, “of what will be a very large iceberg.”

Via National Geographic

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