by Javier Ibarra-Isassi
During my teenage years, I got captivated by the idea of zombies being real. It all started with playing video games, watching movies and reading books about zombies like “The zombie survival guide” by Max Brooks. I talked so much about this topic that my friends started asking me what we would do to survive a hypothetical outbreak and said that they would trust my judgement to save the group. But then, a friend asked me: “do you actually think they are real?”. This got me thinking in a new direction and I started looking about “real-life” zombies.
After some time searching around, I read about the Cordyceps fungi. Most species from this genus are endoparasitoids (a parasite that lives inside another animal) of insects and other arthropods, infamous for taking control of their hosts. One of the most infamous, Ophiocordyceps unilateralis – a complex of many species – attack Camponotini ants, alter their behavior causing them to leave their foraging trails, climb up a bush or tree to bite the major leaf vein on the abaxial surface (underside) of the leaf. The fungus then quickly grows inside the host, replacing its tissues, and erupts a fruiting body containing reproductive spores out of the host’s head. After finding this, every time I hiked around a forest, I searched for a zombified ant as evidence of “real-life” zombies.
A couple of years ago I had the opportunity of going to the cloud forest in Fortuna, Panama, as part of the NEO/BESS Tropical Biology Field Course at STRI. While hiking around, I saw something under a leaf that looked out of place. Upon taking a closer look, I saw a small white dusty bump with a stalk coming out of one side. It was so miniscule that I could not even take a proper picture. Luckily a great mycologist, Dr. Luis C. Mejía, was an instructor during that portion of the field course and confirmed my initial thoughts: it was a parasitized spider! I was stoked to have found evidence of a real-life ‘zombie’, albeit a tiny one.
The white dusty bump that turned out to be a ‘zombified’ spider, around 3mm in length. Chiriquí, Panama. Photo credit: Javier Ibarra-Isassi
Finding the parasitized spider led me to read more about these parasites and the work of Dr. David P. Hughes. I found out that when an insect climbs to the underside of a leaf, it bites into the vein (termed “death grip”) and leaves a distinct bite mark. This has allowed for the identification of the “death grip” in a 48 Ma fossilized leaf found in Messel, Germany. Additionally, I found out that the mechanism through which the fungus parasite manipulates the behaviour of its host is a complex one. Studies point out that there is a downregulation of immune-related, and of maintenance and integrity-related genes. This allows the fungus colony to grow inside the host and to atrophy the mandibular muscles (leading to the “death-grip” phenotype).
Armed with more knowledge, I continued my quest for a real-life “zombie” that was more akin to what I had read about. I had also spent around 5 years looking at ants in tropical forests, so my eyes were a little bit better at spotting small things amidst the leaves. I then had the opportunity to go to the Yasuní National Park, in Amazonian Ecuador to help on a global arthropod monitoring project. During my downtime, I would go out to the trails, looking for the evidence that had eluded me up to this point. While hiking around one day, I spotted a black “twig” beneath a leaf. My heartbeat immediately raised with excitement and wonder. Could this finally be it? Have I finally found what I had read about so many years ago? YES! Low and behold, there it was, a “zombified” Camponotini ant, with the fruiting body of the fungus growing out of its head.
Fungus infected ant biting into the underside of a leaf. Coca, Ecuador. Photo credit: Javier Ibarra-Isassi
Now that I have seen evidence of real-life “zombies” I can return to my friends and tell them they are real. Not in the way we find them in entertainment media, but rather in other interesting ways. Though my quest may feel a little bit more complete now, I will still look beneath leaves and stems when I go around the forest searching for zombies.
Javier Ibarra-Isassi is a PhD Candidate in the Community Ecology and Biogeography lab in the Biology Department of Concordia University. Working under the co-supervision of Dr. Jean-Philippe Lessard (Concordia) and Dr. Tanya Handa (UQAM), he is trying to understand how biodiversity is maintained and influenced by natural and human-influenced processes. For which, he is studying how ant traits and communities vary across broad environmental gradients and how agriculture affects the natural structure of ant communities.