ScienceCast: Zombie Ants

ScienceCast: Zombie Ants

New research has revealed how infection by
a parasitic fungus dramatically changes the behavior of tropical carpenter ants, causing
them to become zombie-like and to die at a spot that has optimal reproductive conditions
for the fungus. A multinational research team including David
P. Hughes, the first author of the paper and an assistant professor of entomology and biology
at Penn State University, studied ants living high up in the rainforest canopy in Thailand.
The behavior of these infected zombie ants essentially causes their bodies to become
an extension of the fungus’s own behavioral traits, as non-infected ants never behave
in this way. “The fungi, which control ant behavior, are
an interesting example of adaptation by natural selection. The life cycle of the fungus begins
with a fungal spore on the forest floor. When the ants are out foraging for food, they pass
through these little ‘killing fields,’ as we describe the fungal spores, and these spores
attach to the ant’s cuticle or its skin. And using a combination of enzymes and mechanical
pressure, the spores force their way through the ant’s cuticle, and into the body.” Using transmission-electron and light microscopes,
the researchers were able to look inside the ant in order to determine the effects of the
fungus. They found that the growing fungus filled the ant’s body and head, causing muscles
to atrophy and forcing muscle fibers to spread apart. The fungus also affected the ant’s
central nervous system. The scientists observed that, while normal worker ants rarely left
the trail, zombie ants walked in a random manner, unable to find their way home. The
ants also suffered convulsions, which caused them to fall to the ground. The researchers also found that, at solar
noon, when the Sun was at its strongest, the fungus synchronized 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 caused fibers within the muscles that open and close the ant’s
mandibles to become detached, causing “lock jaw,” and making an infected ant unable to
release the leaf, even after death. A few days later, the fungus grew through the ant’s
head producing a fruiting body called a stroma, which released spores to be picked up by another
wandering ant. “We’re looking at this phenomenon from a range
of different perspectives. We’re really interested in the biodiversity of these fungi. How many
do we find and whether each ant species that we can encounter in the wild has its own specific
fungal species which is changing its behavior.” Hughes’s continuing research at Penn State
is designed to learn how the fungus might be used to control pest insects in homes and
farms. For ScienceCast, I’m Katrina Voss.

3 thoughts on “ScienceCast: Zombie Ants”

  1. a very interesting piece of info… if fungus can adapt to do this what says fungus cant adapt to do other things? Its all about survivial and everything adapts to survive.

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