AsianScientist (May 9, 2011) – New research published in the journal BMC Ecology looks at how a fungus manipulates ant behavior in Thailand’s rainforests, resulting in zombie ants that walk in a random manner especially at noontime.
Tropical carpenter ants (Camponotus leonardi) live high up in the rainforest canopy. When infected by a parasitic fungus (Ophiocordyceps unilateralis), their behavior dramatically changes. They become erratic and zombie-like, and are manipulated by the fungus into dying at a spot that provides optimal conditions for fungal reproduction.
First, the fungus affects the ant’s central nervous system – while normal worker ants rarely left the trail, zombie ants walk in a random manner, unable to find their way home. The ants suffer convulsions which cause them to fall to the ground, which is cooler and moister than the canopy, providing ideal conditions for the fungus to thrive.
At noon when the sun is at its strongest, the fungus synchronizes ant behavior, forcing infected ants to bite the main vein on the underside of a leaf. The multiplying fungal cells in the ant’s head cause fibers within the muscles that open and close the ant’s mandibles to become detached. The infected ant with a ‘lock jaw’ is then unable to release the leaf even after death. A few days later the fungus generates a fruiting body (stroma) from the ant’s head which releases spores to be picked up by another wandering ant.
“The fungus attacks the ants on two fronts. Firstly by using the ant as a walking food source, and secondly by damaging muscle and the ant’s central nervous system, resulting in zombie walking and the death bite, which place the ant in the cool damp understory,” said Dr. David Hughes, the lead author on the study.
“Together these provide the perfect environment for fungal growth and reproduction. This behavior of infected ants is essentially an extended phenotype of the fungus (fungal behavior through the ant’s body) as non-infected ants never behave in this way,” he said.
The article can be found at: Hughes DP et al. (2011) Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection.
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Source: Biomed Central.
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