Page 33 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

Environment
Rodents of
the undead
Animals are biologically
hard-wired to fear and fl ee
from their predators.
However, one parasite is
capable of reversing a
rodent’s natural fear of
felines, even
encouraging them to
actively seek cats out.
Related to the parasite
that causes malaria,
Toxoplasma gondii is a
single-celled pathogen that
infects many types of mammal
and bird, causing a disease
known as toxoplasmosis. Like
every life cycle, Toxoplasma
has to reproduce, and the only
place that this specifi c microbe
can do so is in the gut of a cat.
When it infects rodents,
Toxoplasma reverses the fear
of cats in a rodent’s brain and
encourages it to seek out
felines by making the rat
attracted to the scent of cat
urine. Inevitably, this results in
the infected rat getting eaten,
allowing Toxoplasma to
continue its life cycle within
the feline hunter.
The zombie ant Death
The fungus then kills its host and uses
How a mind-controlling fungus the nutrients from the ant’s body to
grow a large stroma (a spore-releasing
enslaves carpenter ants, one stalk). This extends down from the back
worker at a time of the ant’s head.
Mind-control
The fungal cells release chemicals
that control the ant’s central
nervous system, forcing it to fi nd a
site where conditions are perfect
for fungal growth. The ant bites
down to anchor beneath a leaf.
Infection Spores scatter
As they forage in their woodland Once the fungus matures, the spores
home, slightly too far from the colony are given off. The fungus is perfectly
for social immunity to protect them, placed to shower the forest fl oor with
worker ants unwittingly get exposed zombie-making spores to enslave
to fungal spores. new ants.
Death-wish fi sh
Killifish in California have been
discovered to play host to a
mind-sucking parasite that alters
behaviour in order to further its
own species. These zombie fi sh
are infected with a fluke – a small,
parastitic worm that reproduces in
the guts of sea birds. The fl ukes
are able to limit the production of
serotonin in the fish’s brain, which
makes it very restless. Ordinarily
shy of the surface and its dangers,
infected fish will actively swim
near and even flick the water’s
surface, greatly enhancing the
changes of getting plucked out
and eaten by a bird.
© Science Photo Library; Corbis; Thinkstock
How It Works 33