Researchers at Penn State University have discovered that the fungal parasite that infects ant and manipulates their behavior to benefit the fungus’ reproduction accomplishes all this without infecting ant’s brain. The researchers said that the zombie-ant fungus surrounds and invades muscle fibers all over the ant’s body, and fungal cells form a 3-D network that might enable them to collectively control host behavior.

Zombie Ants are one of the weirdest species found on Earth and undergo a very strange phenomenon inside their body. These carpenter ants are found in tropical locations and are infiltrated and manipulated by Ophiocordyceps unilateralis sensu lato, also called zombie-ant fungus.

What the fungus does is it forces the ants to forest understory and compels them to climb vegetation and bite into the underside of leaves or twigs leading to the death of the ant. After the ant dies, invasion reaches its peak leads to the sprouting of a spore-laden fruiting body from the dead ant’s head. These infectious pores, when released to the ground, infect other ants and hence the fungus gets benefitted from it. But the astonishing thing is that the infectious fungus achieved all these things without hampering the brain which is known the control the behaviors of an organism.

Lead author Maridel Fredericksen, former master’s degree student in entomology at Penn State, now a doctoral candidate at the University of Basel Zoological Institute, Switzerland, said that to better understand how such microbial parasites control animal behaviour, they looked at cell-level interactions between the parasite and its carpenter-ant host at a crucial moment in the parasite’s lifecycle — when the manipulated host fixes itself permanently to vegetation by its mandibles.

The team first infected the ants with O. Unilateralis s.l. And then used serial block-facing scanning-electron microscopy to create 3-D visualizations and tried to determine the distribution, abundance, and interaction of the fungi inside the ant. David Hughes, associate professor of entomology and biology at Penn State said that a high percentage of cells in host were fungal cells.

The results showed that the fungus cells were present throughout virtually all regions of the host ants’ bodies, including in the head, thorax, abdomen, and legs an also large number of these infectious cells were connected outside the brain but never entered inside the brain. Hughes said that normally in animals, the behavior is controlled by the brain sending signals to the muscles, but their results suggested that the parasite controls host behavior peripherally. Almost like a puppeteer pulls the strings to make a marionette move, the fungus controls the ant’s muscles to manipulate the host’s legs and mandibles. The study was published in the journal Proceedings of the National Academy of Sciences.



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