Research: Evolution of life cycle of that takes over 'zombie ' 3 March 2020, by Collene Ferguson

then commands the insect to climb to the tops of flowers so that a grazing will eat the along with the throng of other parasites hiding inside the ant's body.

Once inside, these peculiar parasites close the life cycle loop by migrating to the animal's liver, where they mature and reproduce, with their eggs being eventually pooped out in the grass to wait for another hungry to eat them.

Credit: Andy Hurly

It could be the plot of a B-horror movie: microscopic parasitic worms invade the brains of ants, and use mind control to make the "zombies ants" do their bidding.

Sounds a little over the top, perhaps, but it is, in fact, the true-life story of the ingenious parasitic , , which is found in increasing numbers in livestock and wildlife in the Cypress Hills region of Alberta and Saskatchewan. Exactly how this parasite has evolved to manipulate the ant to ensure it is eaten by a grazing animal has been a head scratcher for Brad van Paridon collects samples in the field for the researchers. parasite study. Credit: University of Calgary

Parasites have complex life cycles, living inside various at different stages. Dicrocoelium's life cycle is particularly complicated. Research offers insights into parasite's creative It starts life as a microscopic egg in the dung of a survival strategy grazing mammal such as a cow or before infecting and multiplying in and being "The evolution of the zombie ant phenomenon has released in tiny slime balls. Ants love to eat these been a mystery for some time since the parasite slime balls but when they do, they become infected that migrates to the ant brain develops in a way that with myriads of minuscule Dicrocoelium parasites means it can no longer infect the mammalian host," that pass into the ant's abdomen. However, just says Dr. John Gilleard, Ph.D., parasitology one parasite leaves the group and migrates to the professor at the University of Calgary Faculty of ant's brain, essentially turning the insect into a Veterinary Medicine. "Consequently, it's behaving zombie it can control. This single "brain parasite" in an apparently altruistic manner by sacrificing

1 / 3

itself for the benefit of other parasites." ensuring the passing of its genes to the next generation," Gilleard explains. A new study that helps explain how this remarkable parasite's life cycle evolved has just has been These new insights into how the zombie ant published in the Proceedings of the National parasites evolved their eccentric survival strategy Academy of Sciences. are the result of a collaboration across disciplines and universities. "This is a great example of a The study, co-authored by Gilleard, his graduate multidisciplinary project bringing together student Dr. Brad van Paridon, Ph.D., along with co- parasitology, molecular genetics, ecology, and supervisor Dr. Cam Goater (University of evolutionary biology expertise from three Lethbridge) and collaborator Dr. Charles Criscione Institutions," says Gilleard. (Texas A&M University), provides rare genetic evidence to support the theory of "kin selection," Brad van Paridon was a graduate student in the which suggests altruistic behavior can evolve by Host-Parasites Interactions Group, of which his improving the chances of survival and reproduction supervisors Gilleard and Goater are faculty of genetically-related family members. members. The HPI program has as its mission, using parasitology as a platform to prepare the next generation of scientific leaders equipped to address national and global issues of relevance to human, animal, environmental, and economic health.

More information: Charles D. Criscione et al. Clonemate cotransmission supports a role for kin selection in a puppeteer parasite, Proceedings of the National Academy of Sciences (2020). DOI: 10.1073/pnas.1922272117

Provided by University of Calgary Adult Dicrocoelium dendriticum worm that lives in the bile ducts of , sheep, elk, and deer. Credit: Paul Gajda

Self-sacrificing brain worm takes one for the team

This sort of altruistic behavior is common in nature, from sentinel monkeys providing alarm calls, to honey bee colonies where worker bees forage for their queen. But the explanation for how animals evolve to sacrifice themselves for others is a subject of much debate.

"Our research shows that, unlike similar parasites, there is a very close genetic relationship between the parasite in the brain and those in the abdomen. In fact, they are often perfect clones. This means that by sacrificing itself, the 'brain worm' facilitates the survival and reproduction of close relatives

2 / 3

APA citation: Research: Evolution of life cycle of parasitic worm that takes over 'zombie ants' (2020, March 3) retrieved 2 October 2021 from https://phys.org/news/2020-03-evolution-life-parasitic-worm- zombie.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

3 / 3

Powered by TCPDF (www.tcpdf.org)