Researchers in Alberta are studying an unusual parasite capable of manipulating ant behaviour, hoping to uncover the biological mechanisms behind one of nature’s most striking examples of so-called parasitic mind control.
In the Cypress Hills of southeastern Alberta, ants infected with Dicrocoelium dendriticum can be found clinging to vegetation after being driven there by a parasite positioned near their brains. Researchers at the University of Calgary and University of Lethbridge say the organism is particularly remarkable because its behavioural manipulation can effectively switch on and off depending on environmental conditions.
A Natural Drama in Alberta’s Cypress Hills
Rising above the surrounding prairie, Cypress Hills Provincial Park provides a distinctive landscape along the Alberta-Saskatchewan border. At ground level, researchers have been observing a much smaller biological drama.
The parasite Dicrocoelium dendriticum, commonly known as the lancet liver fluke, has a complex life cycle involving several different hosts.
Cameron Goater, a parasitologist and professor emeritus at the University of Lethbridge, said behavioural manipulation by parasites is widespread in nature.
“Almost every taxon [species] of hosts on the tree of life contains parasites or are infected with parasites that lead to manipulation,” said Goater.
In many cases, manipulation allows a parasite to move from one host to another. Well-known examples include Cordyceps fungi, which can cause infected ants to climb vegetation before dying, allowing fungal spores to spread.
Horsehair worms provide another example, manipulating crickets into entering water, where the worms can emerge and reproduce.
Unlike many such relationships, however, Dicrocoelium benefits from keeping its ant host alive.
How the Parasite Moves Between Hosts
Adult Dicrocoelium worms live in the livers of grazing mammals such as elk, deer and cattle. Their eggs leave the animal through feces before being consumed by snails.
Inside a snail, the parasite develops into hundreds of larvae called cercariae. The larvae are eventually packaged in mucus and expelled in slime balls, which can then be eaten by ants.
Most of the parasites settle in the ant’s abdomen, but one larva moves close to the ant’s brain. Researchers refer to this individual as the “brainworm.”
That parasite faces a significant challenge in completing its life cycle.
“The problem is the final host almost never ingests ants,” said Goater. “In many cases, things like deer and elk and cattle actually avoid ants.”
The parasite appears to solve the problem by compelling an infected ant to climb vegetation and lock its mandibles onto the plant. This increases the possibility that a grazing mammal will accidentally consume the ant, allowing the parasites in its abdomen to reach their final host and eventually travel to the liver.
An Unusual Biological ‘On-Off Switch’
Keeping an ant attached to vegetation indefinitely would create another problem. Exposed ants face predators, cannot forage normally and are particularly vulnerable to dehydration.
“The solution to that problem is to detach from a plant and go back to the nest,” said Goater. “That’s where this on-off switch comes from.”
Researchers have observed that infected ants climb vegetation and remain attached when temperatures are below approximately 19 C. As conditions become warmer, the behaviour can stop, allowing the ant to return to its colony.
The ability raises a fundamental question: how does a parasite positioned inside an ant detect external temperature and alter its manipulation accordingly?
“That’s exactly the kind of question that keeps us awake at night,” said Goater, “because it seems that the mechanisms that run that might be something completely new.”
Researchers Look Inside the Ant Brain
Scientists are now investigating what happens at a molecular level when infected ants enter and leave the manipulated state.
One approach involves examining which genes are being expressed during and after the clinging behaviour and comparing those patterns with uninfected ants.
“We’ve gone inside the brain of the ant to try and determine what those changes are from the ant perspective,” said James Wasmuth, a parasitologist at the University of Calgary. “And we see a lot of changes in different biochemical pathways when it’s doing the zombie behaviour.”
Researchers have found indications that an infected ant may not perceive its environment normally while under the parasite’s control. Determining exactly which biological change triggers the behaviour, however, remains difficult.
A Window Into Parasite-Host Biology
The Alberta research could help scientists better understand how parasites interact with the nervous systems and biochemical pathways of their hosts.
For researchers, Dicrocoelium dendriticum stands out because its manipulation does not simply drive its host toward death. Instead, the parasite appears able to alter behaviour according to environmental conditions while keeping the ant alive long enough to improve its own chances of reaching a grazing mammal.
The tiny interactions unfolding among the plants of the Cypress Hills therefore offer researchers an unusual opportunity to investigate how a parasite can influence behaviour — and potentially reveal biological mechanisms that scientists have yet to fully understand.
Francesco Petrarca is a writer for ThePacket.ca, covering news, politics, business, technology, sports, entertainment, and lifestyle. He is committed to clear and reliable reporting, providing readers with useful information, timely updates, and stories that highlight important developments and current affairs.