Science & Tech Editor
You may have seen every zombie movie released in the last decade, and played every game about the undead on the market, but did you know that some of the plots may not be too far from the truth? The fungus, Ophiocordyceps unilateralis, may just be the thing of nightmares. This fungus, dubbed the ‘mind-control fungus’, is actually four distinct species – all of which can control the mind of an ant and turn it into a zombified version of its former self. It thrives in the forests of Thailand and Brazil, and is one of the main biotic factors involved in limiting the growth of ant colonies.
When this Cordyceps fungus infects an ant (usually of the species Camponatus leonardi) a number of events happen; first, the ant suffers severe body convulsions which send it to the forest floor. Next, the ant is made to climb a high tree or stem above its colony. When it reaches a high enough altitude, the poor insect is made to grip on tight to the branch or leaf with its mandibles. The fungus, currently residing in the brain of the ant, kills the bug and begins its growth cycle. Large mycelia then grow from the ant’s head, while fungal hyphae infect the ant’s exoskeleton and strengthen, turning it into a sort of ‘anchor’ for the fungus. Large fruiting bodies grow from the long dead ant corpse and rupture, spewing spores across a large area of the forest. These spores can then infect more ants and send them to a similar doom. This entire process can take between 4-10 days, and if not spotted early can decimate an ant colony.
In response to this dangerous fungus, worker ants have been known to pick up and carry infected ants far away from their main colony and throw them off rocks or branches to lessen the impact of the fungus; the zombie ant, now so disorientated by the fungal secretions in its brain, can’t find its way home and won’t cause as much damage. Infected ants don’t follow the usual behavioural patterns as healthy bugs, and when they aren’t paralysed by convulsions they are often seen to be batting themselves on the head or walking in a spiralling pattern. The most frightening thing is that the fungus isn’t limited to just this species of ants: in fact, it isn’t limited just ants at all! It has been known to affect anything from butterflies and moths to stick insects and tarantulas, and the more of the species there are the higher the chance that it will be attacked by Cordyceps.
Oddly enough, this zombifying fungus is currently under attack from an unidentified ‘hyperparasite’ which severely limits its virulence and interrupts its growth cycle significantly (how’s that for a taste of your own medicine eh?). This “anti-zombie-fungus fungus” moves in to attack the Cordyceps fungus as the stalk emerges from the insect cadaver, and can even be successful in removing the entire fungus from the dead insect and prevent it from releasing any spores.
Fortunately, this fungus isn’t useless, and is thought to have serious medical potential. Not only does the O. unilateralis fungus have an untapped biological source of bioactive metabolites (including antitumor and antimalarial biochemicals), it may actually be HELPING insect species such as C. leonardi by controlling the ant populations and the populations of other insect species. This stops any one species from getting the upper hand on another, and helps maintain a dynamic equilibrium in the dense and damp forests of the South Pacific Ocean.
Having read this article and watched the video, you may ask; could this possibly happen to humans? The answer is maybe. It is possible that by the mechanism of convergent evolution, the Cordyceps fungus could evolve to attack and utilise human hosts as walking-talking spore spreaders. However it is (thankfully) unlikely and were someone to become the real-world ‘Patient-Zero’, quarantine control and our extensive knowledge of anti-biotics would give us the advantage.
If you’d like to view some beautiful photos of the fungus growing out of ant cadavers you can do so at the following link but be warned, it isn’t for the faint of heart or those just after their dinner! Photos