Cognitive Manipulation in Ants: Sophisticated Parasite Modulates Ant Behavior at Specific Times of Day

Credit: Brian Lund Fredensborg

The lancet liver fluke exerts control over ant neural functions, compelling them to attach themselves to blades of grass involuntarily. This parasite exhibits a complex life cycle involving snails, ants, and grazing animals as unwitting participants. Current research is focused on understanding the nuanced methods through which this form of behavioral control occurs.

Visualize an ant, its mandibles clenched tightly to the tip of an oscillating blade of grass, lacking awareness of its circumstances. Such is the fate of ants infested by the lancet liver fluke, a diminutive parasitic flatworm. The intricate life cycle of these liver flukes initiates with the commandeering of the ant’s neural functions. The manipulated ant ascends a blade of grass and latches its strong mandibles onto the tip, thereby increasing the likelihood of its consumption by grazing animals like cattle and deer.

Researchers from the University of Copenhagen’s Department of Plant and Environmental Sciences have unearthed even more sophisticated abilities in this parasite than initially assumed. Notably, the parasite has the capacity to instruct the ant to descend the blade of grass when temperatures rise excessively.

Credit: University of Copenhagen

“Elevating the ants on the grass during the cooler morning and evening hours, suitable for grazing by cattle or deer, and then instructing them to descend to avoid extreme solar exposure, demonstrates an elevated level of intricacy in the parasite,” states Associate Professor Brian Lund Fredensborg, who spearheaded the research in collaboration with former graduate student Simone Nordstrand Gasque, now a doctoral candidate at Wageningen University in the Netherlands.

The research has recently been published in the scholarly journal Behavioral Ecology.

The “Activation/Deactivation Switch”

To conduct the study, the research team tagged multiple infected ants in the Bidstrup Forests, located near Roskilde, Denmark.

“It required considerable skill to adhere colors and numerical labels to the posterior segments of the ants. However, it enabled extended monitoring,” notes Brian Lund Fredensborg.

The team then scrutinized the behavior of infected ants concerning light, humidity, time, and temperature. They found a distinct relationship between temperature and ant activity. In cooler conditions, ants were more likely to remain latched to the grass tip. Conversely, as temperatures increased, the ants disengaged and descended.

“We observed a clear link between temperature and ant behavior, facetiously referring to it as the ants’ activation/deactivation switch,” comments Brian Lund Fredensborg.

Covert Infiltration

Upon entering an ant, the lancet liver fluke disperses several hundred of its kind throughout the ant’s body. However, a solitary fluke journeys to the brain to manipulate the ant’s behavior, while the others remain concealed in its abdomen.

“In essence, a multitude of liver flukes await inside the ant to be transported to their subsequent host. These flukes are encapsulated to safeguard them from the digestive acids of the next host, while the controlling fluke perishes. One could argue it sacrifices itself for the collective,” elaborates Brian Lund Fredensborg.

Exposure to numerous liver flukes can result in liver impairment as the parasites traverse through the host’s liver and bile ducts.

Credit: University of Copenhagen

Significant Ecological Agents

Brian Lund Fredensborg highlights that parasitic behavior modification is more common than generally acknowledged, influencing food chain dynamics substantially. According to him, this study brings attention to a largely overlooked category of organisms.

“Parasites have traditionally been given minimal scholarly attention, despite evidence that they represent a predominant form of life. This is partly because they are complex to study. Nevertheless, these hidden entities constitute a significant segment of biodiversity. By altering host behavior, they indirectly control trophic relationships,” he says.

Research will continue to explore the exact methods through which the lancet liver fluke manipulates ant behavior.

“Our understanding now includes the role of temperature in triggering behavioral changes in ants. However, identifying the specific cocktail of chemicals used by the parasite to induce this zombified state in ants remains an open question,” Fredensborg concludes.

Box: Life Cycle of the Liver Fluke

1. The Zombified Ant: The liver fluke infiltrates the ant’s brain, directing it to attach to a blade of grass, thereby facilitating its ingestion by a grazing animal. A large number of flukes remain in the ant’s abdomen, awaiting transfer.
2. The Grazer: Upon consuming an infected ant, the grazing animal becomes a host to the liver fluke. The controlling fluke is neutralized by stomach acids, while the others are protected by a capsule that dissolves in the intestinal tract. They eventually find their way to the liver, where they develop into adult flukes and commence egg-laying.
3. The Snail: Once expelled via the grazer’s feces, the fluke eggs await a snail to ingest them. They then transform into larval flukes that can multiply into thousands.
4. The Mucous Cluster: To move to the next host, the larval flukes induce the snail to eject them enveloped in a mucus ball. Ants are attracted to and consume this mucus, thereby ingesting the larval flukes.

Reference: “Expression of trematode-induced zombie-ant behavior is strongly associated with temperature” by Simone Nordstrand Gasque and Brian Lund Fredensborg, 24 August 2023, Behavioral Ecology.
DOI: 10.1093/beheco/arad064

Frequently Asked Questions (FAQs) about Parasitic Mind Control in Ants

More about Parasitic Mind Control in Ants

• Behavioral Ecology Journal
• University of Copenhagen’s Department of Plant and Environmental Sciences
• Wageningen University
• Overview of Parasite-Host Interactions
• Ant Behavior and Ecology
• Temperature Influence on Animal Behavior
• DOI for the Original Study