OK, so I will go ahead and admit that I have been saving this article up for a while. I wanted to write about this topic since almost day one, but I could not resist waiting until Halloween to release a story about zombie ants. Yes, you heard me…zombie ants. Just check out the ant featured in the photo above. This is for real, people. Understand that these ants are not the shambling undead, resurrected to lead a ghastly half-life by some dark necromancy, nor have they been reanimated by some unknown radioactivity from outer space. These ants are the victims of a parasitic fungus that is able to alter the behavior of its host. Relating this to zombie movies, these would be more like the “infected” of Danny Boyle’s movie 28 Days Later, rather than the zombies of Romero’s classic Night of the Living Dead. During the process of researching this, I have learned that there are hundreds of identified species of fungi that prey upon insects in this manner (check out the tarantula above, and beetle to the right), and many are very specific in their choice of host. While I would love to discuss as many of them as possible, for the sake of expediency, I am going to focus on ants, about which there is a lot of information available.
We begin the macabre tale of formic terror with the fungus Ophiocordyceps unilateralis (Phylum: Ascomycota, Class: Sordariomycetes, Order: Hypocreales). From what I can tell, the genus Ophiocordyceps is one of at least two genera (another example being the genus Cordyceps) whose members exhibit this fascinating ability. Since mycology is not really my forte, I had to dig around a little to find some clarification on the matter. This particular fungus (O. unilateralis) is usually found in tropical locations (especially in parts of Africa, Brazil, and Thailand), and is a specialized parasite of ants belonging to the genus Camponotus. When a fungal spore becomes established on the ant, it attempts to breach the ant’s exoskeleton. If successful, the fungal mycelium (the fibrous body of the fungus, that also acts rather like the roots of a plant) can grow and spread throughout the body of the insect while simultaneously feeding on it. As the fungus spreads, it gains some measure of control over the ant, though the mechanism by which this occurs has not been explained yet. In this case, the fungus directs the ant to climb up the stem of a plant and then use its powerful jaws to clamp onto the underside of a leaf before the insect dies. Once this happens, the fungus will complete its life cycle, growing a stalk that produces the “fruiting body”, which is where the spores develop. If the ant happens to be positioned over a relatively high-traffic area for ants, then the spores stand an even better chance of finding a new host and renewing the cycle. Below is a great summary of this process, complete with visuals.
While researching this phenomenon, I also encountered this article in which the author suggests that there is fossil evidence demonstrating that this has been taking place for a good 48 million years or so. With the current popularity enjoyed by all things zombie-related these days, this has certainly been a popular story in various blogs and news outlets. A very popular video game, released in June of 2013, was designed around this very idea. Entitled The Last of Us, the game features a post-apocalyptic future where a mutant strain of Cordyceps that can infect and take over humans has driven human beings to the brink of extinction. All said, there has been a lot of hype about these parasitic fungi during the last year or so. To wrap this up, I will leave you with the following video about Cordyceps, narrated by the venerable Sir David Frederick Attenborough:
*I have no idea why I am not able to get this video to embed, so I have made it a link for now. Sorry!*