10 Interesting Facts About Ophiocordyceps unilateralis

Written by: Daksh Verma, Richard Xu, Caleb Ng, Jeffrey Lu, Carmen Chau

1. Ophiocordyceps unilateralis (also known as the “zombie ant fungus”) is a fungal parasite that infects and manipulates formicine ants to achieve its only goal: Reproduction by dispersal (Lu, 2019). This fungus usually infects ants of the Camponotini tribe. There are approximately 1.5 million species of this fungus, however less than 100,000 have been described (Evans, Elliot, & Hughes, 2011).

Image of a dead ant with O. unilateralis growing out of the base of its head. The orange bulb contains spores that are released to infect more ants. Image via David P. Hughes, Penn State University.

2. Ophiocordyceps unilateralis is typically found in tropical environments such. as tropical forests. It is abundant in regions like Thailand, Brazil, Central America and Africa. The ideal temperature range for fungal growth is between 20 and 30 degrees Celsius (Kumlien & Carlson, 2006).

Microscopic views of the parasitic function. Image via João PM Araújo, University of Florida.

3. There are several stages that occur when the fungus infects an ant. First, it releases spores which are then carried through the air until it reaches an ant (Lu, 2019). The spores attach to the cuticle of the ant and then secrete digestive enzymes to break the exoskeleton and enter the host (Kumlien & Carlson, 2006).

4. Once inside the host, O. unilateralis begins the process of taking control of the ant. The parasite emits enterotoxins which are a group of chemicals that disrupt the ant’s chemical communication (Alger, 2015). These toxins force the ant to behave abnormally, including actions such as leaving its nest, excessive twitching and weird walking patterns. Near the end of the ant’s life, the parasite manipulates the ant to search for a humid climate, one that is favorable for the parasite’s reproduction, signaling the end of the ant’s life (Lu, 2019).

5. As the ant dies, the parasite continues to feed on the ant’s insides, enabling O. unilateralis to obtain the necessary nutrients it needs to grow. A few days after the ant’s death, the fungus emerges from the base of the ant’s head to release more spores and infect new unsuspecting ants (Lu, 2019).

Image shows spores being spread from an infected ant to new ants. Image via Tommy Leung

6. Scientists have discovered 200 species of O. unilateralis that can infect a variety of species from spiders to caterpillars (Lu, 2019)

Image shows various Cordyceps species infecting a range of hosts. Image via Shrestha et al.

7. Evidence from fossils have shown that O. unilateralis has been interacting with ants for the past 48 million years (Kumlien & Carlson, 2006).

8. Ants use a “social immunity” technique to deal with O. unilateralis. In order to prevent the entire colony from becoming infected, infected ants are forcibly removed from the nest. This explains why the fungus prefers an elevated position to release its spores: an elevated position allows the spores to affect ants in different colonies (Roehl, 2016).

9. The O. sinensis (another fungus of the same class as the O. unilateralis) is used as a type of traditional medicine in China. There has been research into whether the O. unilateralis can also be used for medicinal purposes (Kumlien & Carlson, 2006).

Image shows O. sinensis (a caterpillar-infecting relative of the O. unilateralis) being used for medicinal purposes. Image via healthline.

10. In the The Last of Us video game series, the parasitic fungus that causes the infection that turns the United States into a post-apocalyptic world is a fictional mutant strain of O. unilateralis (Kumlien & Carlson, 2006).

Image shows humans infected with the fictional parasitic fungus in The Last of the Us (2013). Image via Naughty Dog and Sony Computer Entertainment.

WORKS CITED

Alger, S. J. (2015, October 15). Accumulating Glitches . Nature News. https://www.nature.com/scitable/blog/accumulating-glitches/how_fungus_makes_ant_zombies/.

Evans, H. C., Elliot, S. L., & Hughes, D. P. (2011, September). Ophiocordyceps unilateralis: A keystone species for unraveling ecosystem functioning and biodiversity of fungi in tropical forests? Communicative & integrative biology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3204140/.

Kumlien, A., & Carlson, S. (2006). Ophiocordyceps unilateralis-. Classification. http://bioweb.uwlax.edu/bio203/f2013/kumlien_aaro/classification.htm.

Kumlien, A., & Carlson, S. (2006). Ophiocordyceps unilateralis-. Fun Facts. http://bioweb.uwlax.edu/bio203/f2013/kumlien_aaro/facts.htm.

Kumlien, A., & Carlson, S. (2006). Ophiocordyceps unilateralis-. Habitat. http://bioweb.uwlax.edu/bio203/f2013/kumlien_aaro/habitat.htm.

Kumlien, A., & Carlson, S. (2006). Ophiocordyceps unilateralis-. Reproduction. http://bioweb.uwlax.edu/bio203/f2013/kumlien_aaro/reproduction.htm.

Lu, J. (2019, April 18). How a parasitic fungus turns ants into ‘zombies’. https://www.nationalgeographic.com/animals/2019/04/cordyceps-zombie-fungus-takes-over-ants/.

Roehl, T. (2016, September 13). #006: Zombie Ants. Fungus Fact Friday. https://www.fungusfactfriday.com/006-zombie-ants/.

Yong, E. (2017, November 15). How the Zombie Fungus Takes Over Ants’ Bodies to Control Their Minds. The Atlantic. https://www.theatlantic.com/science/archive/2017/11/how-the-zombie-fungus-takes-over-ants-bodies-to-control-their-minds/545864/.