Zombie ants controlled by fungus manipulating brains


Zombie ants can be controlled by a parasitic fungus, according to a new study. The strange microorganisms reproduce by manipulating the behavior of their hosts, through the release of chemicals capable of controlling brains.

Ophiocordyceps, commonly known as zombie ant fungi, have the ability to cause a host ant to bite down, closing its mandibles. The fungus uses this ability to force the insect to attach itself to a plant, where the tiny animal dies. Ophiocordyceps can then spread to the vegetation, where it can reproduce and exude spores, infecting other ants.

The fungus releases the potent neurochemical when it encounters a Camponotus ant, a potential target for control. The behavior does not take place when an ant of another species appears. This suggests that the microorganisms can recognize their natural host.

"Fungi are well known for their ability to secrete chemicals that affect their environment. So we wanted to know what chemicals are employed to control so precisely the behavior of ants," Charissa de Bekker of Penn State and lead author of the study, said.

Once inside its insect host, the fungus manipulates the brain of the ant, driving the insects toward a nest. Once there, powerful neurochemicals in the brain force the ant to clasp onto a plant or other vegetative matter before the animal dies. The fungus then bursts through the exoskeleton of the deceased insect, and spreads spores into the air to infect other ants.

Camponotus ants, along with members of the Formica species, were infected with the zombie fungus by researchers. The microorganisms infected and killed members of both species, but only controlled the brains of Camponotus.

Ant brains were surgically removed from ants representing a wide range of species. Ophiocordyceps was cultured along with brain material from the different varieties of the common insect. They found the fungus released the brain-controlling chemicals near brains of Camponotus, and no other species.

"There is no single compound that is produced that results in the exquisite control of ant behavior we observe. Rather, it is a mixture of different chemicals that we assume act in synergy," de Bekker said.

Penn State researchers discovered thousands of chemicals take part in controlling the brains of ants. Most of these were previously unknown to science. Two of the substances, an amino acid called sphingosine and the neuromodulator guanobutyric acid (GBA) were found in the compound. These organic chemicals are known to play a role in brain disorders.

Study of the role of neuromodulators on zombie ants was detailed in the journal BMC Evolutionary Biology.

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