The unsuspecting ant climbs up and clamps its powerful jaws onto the top of a blade of grass, making it more likely to be eaten by grazers such as cattle and deer. PHOTO BY UNIVERSITY OF COPENHAGEN/SWNS
A fearsome parasite turns ants into zombies and leads them to their deaths by forcing them to the top of blades of grass where they are eaten by cattle.
The lancet liver fluke hijacks the insect’s brain and is so sophisticated that it can even get the ant to go back down the grass if it gets too hot.
Once the fluke infects the ant, one takes over the brain whilst hundreds of others conceal themselves in a capsule in the insect’s abdomen.
When the ant is eaten by cattle or deer the one controlling the brain dies but the others in the capsule then infect the host animal.
Associate Professor Brian Lund Fredensborg University of Copenhagen’s Department of Plant and Environmental Sciences said: “Imagine coming to, jaws gripping the top of a swaying blade of grass, unaware of how you got there.
“That’s the reality for ants infected with the lancet liver fluke, a tiny parasitic flatworm.
“The unsuspecting ant climbs up and clamps its powerful jaws onto the top of a blade of grass, making it more likely to be eaten by grazers such as cattle and deer.
“Getting the ants high up in the grass for when cattle or deer graze during the cool morning and evening hours, and then down again to avoid the sun’s deadly rays, is quite smart.
“Our discovery reveals a parasite that is more sophisticated than we originally believed it to be.”
Liver flukes have a complicated, almost insanely conceived life cycle, which begins with the hijacking of the ant’s brain.
Once in the mammal host they reproduce and the eggs are excreted out. These are then eaten by snails and the eggs turn into hundreds or thousands of larval flukes.
The flukes cause the snail to cough, expelling them in a lump of mucus which is attractive to ants that eat it and become infected.
However, the team discovered that the parasite’s ability to control the ant is even more cunning than previously believed.
The study of the parasite has just been published in the scientific journal Behavoral Ecology.
Fredensborg said: “We found a clear correlation between temperature and ant behavior.
“We joked about having found the ants’ zombie switch.”
The researchers tagged several hundred infected ants in the Bidstrup Forests near Roskilde, Denmark, gluing colors and numbers onto the rear segments of the ants to keep track of them.
They then observed the infected ants’ behavior in relation to light, humidity, time of day and temperature.
It was clear that temperature had an effect on ant behavior. When the temperature was low, the ants were more likely to be attached to the top of a blade of grass.
When the temperature rose, the ants relinquished the grass and crawled back down.
Detailing the ‘Trojan Horse’ deception to get into mammals, Fredensborg said of the hidden capsule: “Here, there can be hundreds of liver flukes waiting for the ant to get them into their next host.
“They are wrapped in a capsule which protects them from the consequent host’s stomach acid, while the liver fluke that took control of the ant, dies.
“You could say that it sacrifices itself for the others.”
Animals infected with many liver flukes can suffer liver damage as the parasite moves around the host’s liver and bile ducts.
He added: “Historically, parasites have never really been focused on that much, despite there being scientific sources which say that parasitism is the most widespread life form.
“This is in part due to the fact that parasites are quite difficult to study.
“Nevertheless, the hidden world of parasites forms a significant part of biodiversity, and by changing the host’s behavior, they can help determine who eats what in nature. That’s why they’re important for us to understand.”
The tiny liver fluke is widespread in Denmark and other temperate regions worldwide.
Fredensborg added “We now know that temperature determines when the parasite will take over an ant’s brain.
“But we still need to figure out which cocktail of chemical substances the parasite uses to turn ants into zombies.”
Produced in association with SWNS Talker
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