Once an ant has been sprinkled with its spores, the parasitic fungus Ophiocordyceps unilateralis penetrates the cuticle and begins to infect the ant’s brain. It directs the ant upwards, where its deadly spores will have the most reach. Once they’re high enough, the zombie ant bites down and grips the stem with its mandible, anchoring them in place. The ant dies as the fungus takes over its body, and eventually, the parasite’s large stalk erupts right through the back of the ant’s head. When the parasite is done growing, its deadly spores burst from the tip, dispersing more death to the jungle floor. The cycle continues with any nearby ants.
Here’s an amazing, eerily beautiful video of parasitic fungi and a poor bullet ant (Paraponera clavata) colony. You can see the fruiting body of the fungus erupt from an ant’s head around 1:02. The time-lapse compresses the 3-week process into a few creepy seconds. (The genus name has since been updated from Cordyceps to Ophiocordyceps.) From the BBC:
If infected individuals are discovered, the workers take them away far from the colony. After all, the fungus can wipe out an entire colony. And not just ants: Thousands of different types of parasitic fungus specialized on individual species. As Sir David Attenborough mentions, parasites like these stop any one animal from getting the upper hand. The more numerous the species becomes, the more likely it will be attacked.
These “graveyards on the move” were described in a 2009 PLoS ONE study.
Image: David P. Hughes, Maj-Britt Pontoppidan via Wikimedia