Parasitic Tapeworms Alter Behaviors and Lifespan Of Infected and Uninfected Ants

Parasites do not always harm their hosts but that's certainly not the case when it comes to a particular type of tapeworm that can kill ants and wreak havoc even on the uninfected. Parasitic tapeworms are known to use Temnothorax nylanderi ants as intermediate hosts during early stages of development, at which time the infected ants' behavior and appearance is altered. However, researchers from Johannes Gutenberg Universitaet Mainz (JGU) recently discovered this parasitism also impacts uninfected ants and causes entire colonies to lower their guard against predation.   

Temnothorax nylanderi ants are native to Western Europe and are generally brown in color. When paralyzed by the Anomotaenia brevis tapeworm the ants turn a dull yellow color and become rather inactive, remaining in their nest where they barely participate in social activities, such as caring for the brood or gathering food. This "lazy" lifestyle not only facilitates the tapeworm's growth, but it makes the ants more susceptible to being eaten by woodpeckers – which is actually the parasite's main host, according to a news release.

"The parasites have developed fascinating strategies to protect their interests and so ensure, for example, their proliferation," Professor Susanne Foitzik, one of the study's researchers, explained in the release. "They attempt to influence the ants in such a way that they are more likely to be eaten by a woodpecker."

For their study, researchers studied ants living in the Lennebergwald forest, a wooded area of 700 hectares north of the city of Mainz, where a third of all ant colonies contain the parasite and nearly 13 percent of the insects are infected. When simulating woodpecker attacks on ant colonies hidden under acorns or dead wood on the forest floor, researchers found Temnothorax nylanderi ants exhibited reduced flight behavior.

Oddly, however, infected ants tend to live longer than their uninfected counterparts.

"The longer lifespan may be due to modified genetic regulation but could also be the result of the fact that the infected insects enjoy a better level of feeding," Sara Beros, lead author of the study, added in the university's release.

So how do Anomotaenia brevis tapeworms impact entire colonies? Researchers say it's "the parasite's long arm." This means that uninfected ants are under more stress to pick up the slack and are confused by the different scents infected ants emit, meaning they are not ready to defend their colony against intruders.  

The study was recently published in the Proceedings of the Royal Society B: Biological Sciences.

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