What To Expect When Expecting A Zombie: The Zombie Ant

From “The Walking Dead” to “iZombie”, zombies are your typical sci-fi fair that takes on different roles from monsters to victims and continues to excite and entertain us. There are insurance companies that offer zombie insurance should a zombie outbreak ever occur. Even the Center for Disease Control and Prevention (CDC) has a zombie preparedness website ready for us should we feel the need to prepare for a zombie apocalypse (or any other disasters that may strike). But the real question for us is can zombies actually exist? The short answer is yes…in a way. While the zombies that are seen on television and film are pretty far-fetched ideas, there are creatures that resemble zombies in a fashion. The zombie for today will be the carpenter ant, which has become infected and turned into a zombie by a fungus. The fungus in question is Ophiocordyceps unilateralis, aka the zombie fungus.

O. unilateralis is a host specific pathogenic fungus that preys on carpenter ants [1]. It was discovered by British naturalist Alfred Russel Wallace in 1859. The zombie fungus thrives in tropical forest environments like the Amazon rainforest or the rainforests in Thailand (home of the carpenter ants). Like in the movies, the main goal of the zombie fungus is to infect a host and control it in such a way that allows it spread its spores and infect more hosts with the hope that it can infect the entire ant colony and create a large zombie-ant pandemic. This is wonderful for the fungus and not so great for the ant because the ants always die in the end.

This all starts when an unsuspecting ant is out foraging for food and comes into contact with the spores of the zombie fungus [2]. The spores release an enzyme that eats through the exoskeleton of the ant and enters its body. Once the fungus has entered the ant’s body, it travels throughout it and eventually gets to the brains of the ant. When it reaches the brain, the fungus releases chemicals that take control of the ant, removing any and all of the ant’s control over its own body [2]. The ant then displays some zombie behaviors: random walking, convulsions, erratic behavior, and a disregard for its own well-being [3]. The fungus then forces the ant to move towards lower areas that are more humid and have the right temperature for the fungus to grow. Once it is ready, the fungus will cause the ant to clamp down on a leaf stem abruptly and strongly (its “death grip”) so that when the ant eventually dies, it will not fall down from the leaf and remain there for weeks [3]. Once the ant is dead, the fungus will liquefy the internal organs and break it down into sugar to feed all of the fungi cells [4]. The outer shell will remain to protect the fungus and keep others out. After a few days of feasting on the ant, the zombie fungus will grow a stroma, a stem-like structure, that will push through the skull of the ant and extend past it (see image above) [4]. After a week, spore clusters on the stroma will be released onto the forest floor, where the ants forage, and the process will start all over again [4].

The carpenter ants are not without their own defenses for dealing with this threat. They have evolved to identify infected ants and avoid dead ants with stems growing out of their heads [4]. This is also one of the reasons the ants build their homes in high canopies so that they can avoid the spores from landing on them as they fall from the stroma. There are no indications that any infected ants are able to resist the infection and not become a zombie so avoiding the spore is their primary defense.

There are many other fungi related to this one and others not related that act as zombie fungi and attack their own specific hosts [5]. Like the T-virus in “Resident Evil”, we also study the zombie fungi because they can potentially have medicinal qualities like combatting malaria or fighting cancer [1]. Fortunately for us, the fungus only operates on ants and its zombie abilities are not compatible with humans. However, this does give credit to the idea that there may be other mind controlling parasites/pathogens that exist in the world. With global warming releasing bacteria and other microscopic organisms from their frozen sleep, who knows what we will one day find.

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