Of Walkers and Other Zombies

Many zombie apocalypse movies and tv shows have captured our attention, and I don’t know about you, but many times I find myself thinking about possible scenarios. What would I do? Where would I go? Is the Gamboa School House even prepared to sustain such event? Probably not. Being afraid of a zombie apocalypse might sound like an irrational fear to some…but don’t be foolish: zombies are around us.

According to Smith (2015), three characteristics make a zombie a zombie: body that came back to life, being infectious and aggressive. Invertebrate zombies are slightly different, mainly because they are not resurrected, but rather they succumb to an infective agent that alters their behaviour. There exist hundreds of species of fungi that exploit this strategy around the world, especially in tropical regions. There are at least two genera (Ophiocordyceps and Cordyceps) of zombie fungi and some species can be extremely host specific (Sung et al 2007; Evans et al 2012).

 

Life Cycle of the Zombie Fungus

The life cycle of the zombie fungus is quite intricate and it starts when a potential host comes in contact with fungal spores. The fungal spore germinates and if successful at breaking the host’s exoskeleton, it parasitizes the invertebrate. The fungus can alter the behaviour of its host; however, the mechanisms used to alter behaviour are poorly understood (Andersen et al 2009; Pontoppidan et al 2009). Ants parasitized by Ophiocordyceps unilateralis, for example, leave their colonies and bite the underside of a leaf, where they will die to benefit the fungus (Andersen et al 2009; Pontoppidan et al 2009). Then, the fungus shoots a reproductive structure through the ants head (Andersen et al 2009). After maturation, the fungus releases spores onto the forest floor and the process starts all over again (Andersen et al 2009).

howtomakeazombieant

 Life cycle of Ophiocordyceps unilateralis  (From D.P. Hughes, Harvard University)

 

The fungus we found in Pipeline Road was parasitizing a moth. With Luis Mejía, we will try to isolate the fungus and run some experiments to try to understand what mechanisms are used by the fungus to alter host behaviour.

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Zombie moth in situ (Photo by Brandon Varela)

Close ups of the fungal growths through a microscope (Photos by Brandon Varela).

 

Literature Cited

Andersen, S.B., Gerritsma, S., Yusah, K.M., Mayntz, D., Hywel-Jones, N.L., Billen, J., Boomsma, J.J., and Hughes, D.P. 2009. The life of a dead ant: the expression of an adaptive extended phenotype. The American Naturalist 174(3):424-433.

Evans, H.C., Elliot, S.L., and Hughes, D.P. 2011. Hidden diversity behind the zombie-ant fungus Ophiocordyceps unilateral: four new species described from carpenter ants in Minas Gerais, Brazil. PLoS ONE. DOI: 10.1371/journal.pone.0017024

Pontoppida, M.B., Himaman, W., Hywel-Jones, N.L., Boomsma, J.J., and Hughes, D.P. 2009. Graveyards on the move: the spatio-temporal distribution of dead Ophiocordyceps-infected ants. PLoS ONE 4(3): e4835. DOI: 10.1371/journal.pone.0004835

Smith, T.C. 2015. Zombie infections: epidemiology, treatment, and prevention. BMJ; 351: h6423. DOI: http://dx.doi.org/10.1136/bmj.h6423

Sung,  G.H., Hywel-Jones, N.L., Sung, J.M., Luangsa-ard, J.J., Shrestha, B., and Spatafora, J.W. 2007. Phylogenetic classification of Cordyceps and the clavicipitaceous fungi. Stud Mycol 57:5-59. DOI: 10.3114/sim.2007.57.01

 

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