In the southeastern region of Alberta, the Cypress Hills stand out prominently amidst vast prairies. Below the striking landscape lies a captivating scenario of ants involuntarily clinging onto plants and shrubs within Cypress Hills Provincial Park, awaiting consumption by unsuspecting herbivores. The parasite responsible for this eerie phenomenon is Dicrocoelium dendriticum, showcasing exceptional abilities in manipulating its host.
Researchers from the University of Calgary and University of Lethbridge have identified this parasite as a standout in the world of parasitic manipulations due to its unique capability to switch control on and off, a feature unparalleled in the realm of zombies.
The presence of zombie parasites in nature is widespread, according to Cameron Goater, a parasitologist and professor emeritus at the University of Lethbridge. Various hosts across the tree of life harbor parasites that induce manipulation, often aiming to transition from one host to another. Notable examples include the Cordyceps fungus, known for compelling infected ants to climb plants and perish to spread spores, and the horsehair worm prompting crickets to leap into water for mating opportunities.
Unlike many other parasitic interactions resulting in host death, Dicrocoelium operates differently by ensuring host survival to complete its complex life cycle involving multiple hosts. The lifecycle includes adult worms residing in the livers of grazing mammals, with eggs excreted and ingested by snails, developing into larval forms called cercaria. These larvae are consumed by ants, where all but one migrate to the abdomen while a “brainworm” positions itself near the ant’s brain.
The challenge arises as the final host, typically grazing mammals, seldom consume ants. To overcome this hurdle, the brainworm triggers the ants to climb plants, increasing the likelihood of accidental ingestion by herbivores.
However, this strategy poses risks to the ants, exposing them to predators, hindering their ability to feed, and making them prone to dehydration. To combat these challenges, the ants exhibit a remarkable behavior of detaching from plants and returning to their nests, showcasing an intriguing on-off mechanism.
The parasitologists delve into unraveling the underlying mechanisms by studying gene expression during the clinging behavior, emphasizing the complexity of biochemical pathways involved. These subtle changes orchestrated by parasites like Dicrocoelium highlight the intricate manipulation techniques employed to ensure successful transmission.
While much remains to be uncovered, researchers are optimistic about identifying key molecules such as adenosine and pathways linked to smell, metabolism, and circadian rhythms in understanding the parasitic influence on host behavior. The intricate relationship between parasites and hosts offers valuable insights into brain function and potential vulnerabilities to manipulation, transcending beyond the realm of insect interactions.
The presence of Dicrocoelium in Cypress Hills serves as a poignant reminder of human interventions influencing natural ecosystems, potentially creating conducive environments for parasitic spread. By examining the intricate interplay of factors facilitating the parasite’s establishment in unique ecosystems, researchers aim to glean insights applicable to managing emerging diseases and understanding the repercussions of human-induced alterations on wildlife habitats.
