Brain-encapsulating liver fluctuations change the behavior of infected zombie ants to avoid high temperatures
Infected Formica polyctina The ant climbs and attaches its powerful jaws to the top of a patch of grass, making it more vulnerable to being eaten by grazers such as cattle and deer. Image credit: University of Copenhagen.
Once Dendritic diploid Affects A Formica polyctina Ant, several hundred parasites invade the ant’s body.
But only one makes its way to the brain, where it can influence the ant’s behavior. As for the rest of the liver worms, they hide in the ant’s stomach.
“There could be hundreds of liverworms waiting for the ant to introduce them to its next host,” said Dr Brian Lund Fredensborg, a researcher at the University of Copenhagen.
“It is encased in a capsule that protects it from the stomach acid produced by the host, while the liver fluke that has taken over the ant dies. You could say it is sacrificing itself for others.
“Animals infected with multiple helminths can suffer liver damage when the parasite moves around the liver and bile ducts of the host.”
Over 13 non-consecutive days during one year in the Bedstrup forests near Roskilde, Denmark, Dr. Fredensborg and his colleague Ph.D. from Wageningen University. Student Simone Nordstrand-Gaske observed a total of 1,264 individual ants expressing the modified behavior. They then individually marked a subset of 172 infected ants.
“It took some ingenuity to stick the colors and numbers onto the back parts of the ants, but it allowed us to track them for longer periods of time,” Dr Fredensborg explained.
The researchers then observed the behavior of the infected ants in relation to light, humidity, time of day, and temperature. It was clear that temperature had an effect on the ants’ behaviour.
When the temperature was low, the ants were more likely to stick to the highest patch of grass. When the temperature rose, the ants left the grass and crawled back down.
Dr Brian Lund Fredensborg, a researcher at the institute, said: ‘Getting the ants high in the grass when cattle or deer are grazing during the cool morning and evening hours, and then back down to avoid the sun’s deadly rays, is very clever.’ University of Copenhagen.
“Our discovery reveals a more advanced parasite than we originally thought.”
There are many other examples of parasites that change animal behavior. As such, parasites that control their host’s behavior have a larger role in the food chain than many might think.
“Our new study highlights a group of creatures that have been greatly underestimated,” Dr Fredensborg said.
“Historically, parasites have never been focused on as much, even though there are scientific sources that say parasitism is the most widespread form of life. This is partly because parasites are difficult to study.”
“However, the hidden world of parasites makes up an important part of biodiversity, and by changing host behaviour, they can help determine who eats what in nature. That’s why it’s important for us to understand.”
The results were published in the journal Behavioral environment.
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Simon Nordstrand Gaske and Brian Lund Fredensborg. The expression of trematode-induced zombie ant behavior is closely related to temperature. Behavioral environment, published online August 24, 2023; doi: 10.1093/beheco/arad064
