Ophiocordyceps unilateralis - The Zombie Ant fungus
So I’m kicking off my geeky biology facts with an old favourite. This was one of the first things that blew my mind at university and I still find it fascinating and exciting to this day. This is Ophiocordyceps unilateralis…
Ophiocordyceps unilateralis is a fungal pest that infects insects and changes the behavioural patterns of the host. Using ants as an example (as they are the most common insect to be infected by this fungus) the infected ant will leave its canopy nests and foraging trails for the forest floor, an area with a temperature and humidity suitable for fungal growth, here the ant will fix its mandibles into the vein of a leaf and stay there till death (1). The death of the ant is not a quick process however, it can take up to 4 - 10 days for the ant to die, within this time the fungus undergoes a fruiting and reproductive phase. Here the fungus grows and “blossoms” (for want of a better word) by erupting from the ants head and/or thorax! At this time, O. unilateralis releases spores to the surrounding area, to then infect another insect.
If you were born in the 90’s or a bid nerd like me you might think “that sounds familiar” and that’s because it is the basis of this Pokemon line …
Yep even back when Pokemon started, they used this concept to design one of the original pokemon, it is literally an insect with a parasite in it and as the parasite grows it takes over the mind and zombifies it - hence the white eyes on Parasect.
Back to the ants, as this is such a destructive parasite to an ant colony, the ants have developed a way to detect or sense when a member is infected, the healthy ants then carry the infected ant away from the colony and the normal paths the ants take, as to not infect any more of the colony when the fungus erupts and spreads spores around the colony (2,3)
Finally it’s not just the ant that has to fight through this infection, the fungus also has to put in a lot of work to get to the fruiting stage. The fungus must first attach securely to the arthropod exoskeleton and penetrate it—avoiding or suppressing host defenses—then, control the behavior of the host before killing it; and finally, it must protect the carcass from microbial and scavenger attack(4). To me this is very fascinating fungus and was one of the things that made me go “wow” at University because it can show you how much of a horror nature can be.
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So I’m thinking of doing these every monday, i feel like it should have a title to it or a hashtag to it but for now I’ll just call it a geek out for now as that is what it is. Let me know if you like these and want to see more or if you have any topics you want me to cover.
1) Mongkolsamrit, S., Kobmoo, N., Tasanathai, K., Khonsanit, A., Noisripoom, W., Srikitikulchai, P., Somnuk, R., Luangsa-ard, J. J. (2012). “Life cycle, host range and temporal variation of Ophiocordyceps unilateralis/Hirsutella formicarum on Formicine ants”. Journal of Invertebrate Pathology. 111 (3): 217–24
2) Pontoppidan, M. B., Himaman, W., Hywel-Jones, N. L., Boomsma, J. J., Hughes, D. P. (2009). “Graveyards on the move: The spatio-temporal distribution of dead Ophiocordyceps-infected ants”. PLoS ONE. 4 (3): e4835.
3) Sung, G. H., Hywel-Jones N. L., Sung, J. M., Luangsa-Ard, J. J., Shrestha, B., Spatafora, J. W. (2007) “Phylogenetic classification of Cordyceps and the clavicipitaceous fungi”. Studies in Mycology. 57 (1): 5–59.
4) Evans, H. C., Elliot, S. L., Hughes, D. P. (2011) “Ophiocordyceps unilateralis – A keystone species for unraveling ecosystem functioning and biodiversity of fungi in tropical forests?”. Communicative Integrative Biology. 4 (5): 598–602
Pictures obtained from google.
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