Scientists in Denmark have discovered two new species of deadly fungi that devour from the inside, exploding from the abdomen of their prey still alive.
The parasites – Strongwellsea acerosa and Strongwellsea tigrinae – infect adult flies, which continue to buzz for days with massive holes in the body.
As they do so, the fungus rains spores from these holes into other unsuspecting flies.
Thousands of torpedo-shaped spores can fire like a single-fly rocket.
Researchers believe that flies are kept alive by potent drug-like chemicals secreted by fungi that also keep other microorganisms away from the wound site.
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The corpse of a fly with two large holes in the abdomen, caused by the fungus Strongwellsea tigrinae. After cutting its host, the parasite keeps it alive and doped, so it can buzz around and throw spores at other unsuspecting flies.
Researchers at the Museum of Natural History in Denmark and the Department of Plant and Environmental Sciences at the University of Copenhagen have reported on the two new fungi.
“They work like little rockets,” University of Copenhagen ecologist Jørgen Eilenberg told The Guardian.
“They’re almost torpedo-shaped and designed to go fast.”
“If they land on another fly, they stick to the cuticle and then head to the abdomen, where they begin to proliferate.”
“Thousands of spores will be released from a single fly.”
Strongwellsea acerosa spores. Fungi pass through cold Danish winters as thick-walled orange spores that germinate in spring
One species, Strongwellsea acerosa, was discovered on Amager, the most densely populated island in the country and home to its captive population, Copenhagen.
The other, Strongwellsea tigrinae, was found in Jægerspris, a more rural area in the north.
Host-specific fungi only infect two species of Danish flies, Coenosia testacea and Coenosia tigrina.
The host-specific fungus Strongwellsea tigrinae (lower) only infects adult flies of Coenosia tigrina. Researchers believe that only 3 to 5 percent of the fly population is infected, enough for the fungus to spread.
As they do so, they create a large hole in their host’s abdomen.
But the open wound does not kill the fly, but turns it into a “zombie,” which surrounds itself by throwing more fungal spores into the air and onto new victims.
Fungi feed on the body of their guests to the end.
After a few days, the fly finally comes off, falling on its back and sprouting in the last hours before dying.
“This is an exciting and strange aspect of biodiversity that we have discovered in Denmark,” Eilenberg said.
“By itself, this mapping of new and unknown biodiversity is valuable. But at the same time, it is new basic knowledge that can serve as a basis for experimental studies of the pathways of infection and the bioactive substances involved.”
Strongwellsea acerosa (bottom) of the adult flies of Coenosia testacea. Researchers believe the fungus secretes substances that keep its host alive and fly alive and other microorganisms away from the wound area
The fungi traverse the cold Danish winters with the help of their thick-walled orange spores and germinate in the spring.
Eilenberg believes they do not infect many of the flies, perhaps three to five percent, enough to spread.
“It’s fascinating how the life cycles of these fungi adapt so well to the life of the flies they target,” he said.
Ironically, the horrible life cycle of these parasites can have health benefits for humans.
Researchers believe that fungi emit an amphetamine-like substance to keep guests running even while they devour their insides.
They are also likely to produce something to keep other microorganisms away from the wounds of flies.
“We would certainly like to continue our research, as doing so has the potential to discover and make use of these substances, perhaps in medicine,” Eilenberg said.
The findings have been published in the Journal of Invertebrate Pathology.
This is not the only fungus that turns its host into a zombie fly: another genus, the massospore, which uses cicadas in a similar way.
Another fungus, the Cordyceps, also infects flies, but as a larva.
Another deadly fungus, Cordyceps, infects the larva of the fly. When the fly matures, it takes control of its muscles, forcing it to climb the plant. It then sprouts antenna-like stems through its victim’s exoskeleton, which shoots spores into the ground to infect more insects.
Once the fly matures, the fungus controls its body, forcing it to walk to the top of a plant, grab it and wait to die.
The cordyceps then sprout antenna-like stems through their victim’s exoskeleton, which then release spores into the ground below, where the fungus can infect more insects.
Experts originally thought Cordyceps was infecting the brains of its guests, but research published this month showed that it actually takes over the muscles of its victims.
The researchers described this behavior as “like a puppeteer pulling the strings to move a puppet.”