The Walking Dead

January 17th, 2013

The Walking Dead. Based on a true story.

Ophiocordyceps unilateralis, also known as cordyceps, is a type of fungus that infects insects and takes over their nervous systems. The method with which they take control of nervous systems is still a mystery to science. However, the repercussions of such an infection are all too clear.

Carpenter Ants, for example, live in the canopy of the tropical rainforest. They frequently forage for food on the forest floor. Unfortunately, this is where the cordyceps fungus proliferates. A new study shows that the fungus prefers to grow on “the undersides of leaves sprouting from the northwest side of plants that grow on the forest floor” This places it in an ideal position to grow and release its spores to infect ants. Here’s how the fungus gets there in the first place.

When an ant is infected by cordyceps, it undergoes a series of behavioural changes. The fungus forces the ant to climb down from the canopy to the low leaves where the cordyceps prefers to grow. Just before dying, the ant will use its mandibles to bite down on the leaf to secure itself.

After the zombie ant dies, the fungus digests the insides of the ant to get nutrition for growth. It’s interesting to note that the cordyceps avoids digesting the muscles controlling the ant’s mandibles. These muscles are the ones that keep the ant attached to the surface. The outer husk of the ant is also left unharmed. The cordyceps uses this as a physical armor to protect against microbes and other fungi.

The fruiting body of the cordyceps will then erupt from the ants head, slowly growing longer until it matures, after which it will release the spores, which seek new hosts. Any ant in the vicinity of this event risks infection.

A single ant infection is a threat to the whole colony. As such, ant colonies go out of their way to avoid an epidemic. Worker ants will often carry an infected ant far away from where the colony forages to prevent the spread of the fungus. The fact that Carpenter Ants live in the canopy of the rainforest may be a strategy to escape the infection.

Cordyceps does not exclusively target Carpenter Ants. There are many different types of Cordyceps fungi that can infect many different insects, including moths, grasshoppers and many more.

Read all about it:

Also, a video of Sir David Attenborough narrating the infection process:

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