Parasitic worms that zombify ants to do their bidding may be even smarter than we knew. Recent research has found that these parasites can not only force ants to climb up blades of grass, but also climb back down when the weather gets too hot – all as part of their devious strategy of getting eaten by larger animals to continue their complex life cycle. .
The parasites are a type of flatworm known as a lanceolate fluke (Dicrocoelium dendriticum). These worms primarily live their lives as adults inside cows or other grazing ruminants, but long way get there
The worm eggs that the cows poop end up in the grass where the snails eat them. The worms reach their next larval stage inside the snail and reproduce asexually into thousands more. Snails respond to attack by forming hard cysts around the intruders, which are coughed up as slimy balls of mucus. These slime balls are then unknowingly eaten by the ants along with the worm larvae.
Once the ants are inside, the larvae enter their next stage of life. Most of them migrate into the ant’s stomach, safely cocooned, but one gets into the brain and hijacks it. An attacked ant is forced to climb to the top of a nearby blade of grass and grasp it, providing an easy opportunity for wandering ruminants to inadvertently eat the ant and its worm parasites. These thrice-consumed worms finally reach adulthood inside their final host, move down into the liver, feed, mate, and lay eggs that start this gruesome cycle again (the actual brain worm sacrifices itself for its brethren and doesn’t survive the final leg of the journey).
While the basic details of the life cycle of the lancelet fluke are known, scientists do not understand much about this complicated process. A team of researchers from the Department of Plant and Environmental Sciences at the University of Copenhagen therefore decided to take a closer look. They studied more than 1,000 infected ants in the Bidstrup forests near Roskilde, Denmark, for 13 consecutive days over the course of a year, carefully marking a subset of 172 ants for better observation.
The team hypothesized that several factors, such as humidity and time of day, might influence the behavior of infected ants. However, temperature seemed to have the biggest effect. On relatively cool days, the ants remained attached to the grass almost the entire time. But when the weather warmed, the ants crawled back down and seemed to go about their normal business. This meant that the ants were the worms most often pupated at night and in the morning.
“Getting the ants high up in the grass when cattle or deer are grazing in the cool mornings and evenings, and then down to avoid the deadly sun’s rays, is pretty clever. Our discovery reveals a parasite that is more sophisticated than we originally thought it was,” said study author Brian Lund Fredensborg, associate professor at the University of Copenhagen. declaration. “We joked about finding the zombie switch in the ants.
Finding, published last month in the journal Behavioral Ecology highlighted how little we still know about parasites in general, the authors say. And it will take more research to unravel the specific mechanisms these flukes use to zombify ant brains.
Fortunately, you don’t have to worry about these randoms turning you into a zombie. People do occasionally infest by them, which can sometimes cause serious damage to the liver and bile ducts. However, these infections are rare and humans are only an accidental primary host for the worm.
