Carpenter ants are known to 'transform' into zombie ants when infected by a parasitic fungus of the genus Ophiocordyceps that are also called zombie ant fungi. When an ant encounters the fungal spores, it gets infected, and the infection rapidly spreads to the other parts of the ant's body. Zombie ants, once infected, forcefully clamp their jaws into a leaf or a twig and just wait until they die.
Before, scientists believed that this 'jaw lock' action of the ants once infected is due to the release of chemicals caused by the fungal infection, thus the fungus manipulates the mind of the ant. However, just recently, scientists have investigated this work of nature and found that the fungus does not control the mind of the ant. Instead, it controls the muscles in the jaws of the ant.
In uninfected carpenter ants, the jaw muscles appear stripy and striated-that is, it is layered-as seen under an electron microscope. A molecular biologist at Penn State University Colleen Mangold said that upon the time that the ant forces its jaw on a leaf or a twig, the muscle stripes appear very swollen. They found that the fungal infection causes physical damage to the jaw muscles but does not appear to interfere with the relay of information between the brain and the muscles. The brain does not seem to communicate with the muscles when the ant does this.
It is not yet known how the fungus controls the muscles enough to make the ant forcefully bit on a leaf or a twig and not leave afterward. But scientists are looking at how tiny particles that look like a small clump of grapes appear on the infected and swollen muscle fibers of the jaw. Mangold and her team suspect that these particles may be extracellular vesicles and may have been produced by either the invader (the fungus) or the host (the ant). And if they are, indeed, extracellular vesicles, they may contain a chemical compound, a message, or whatever it is that is used by the fungus to manipulate the action of the ant, and these clusters of particles therefore play a role in finding out how the fungus actually controls the ant's jaw muscles.
