As popular horror genres go, there are none bigger than that of the ‘post-apocalyptic Zombie’, with the likes of Zombieland and World War Z dominating cinema screens in recent years. However, with Halloween approaching it’s perhaps a fitting time to consider nature’s real life Zombies – in particular a fungi family which can wipe out entire ant colonies, turning them into 6-legged versions of the walking dead.
The fungi – named ‘Cordyceps’ – affect a variety of insects, prompting parasitic growths within their chosen host, manipulating their behaviour whilst feeding off its non-vital organs. Fungal spores attach themselves to the external surface of their victim, where they germinate before entering the ant’s body through its trachea. Once inside, the germinated spores begin to produce fine fungal threads, called mycelia, which start to grow inside the ant’s body cavity. The threads absorb the host’s soft tissues whilst avoiding the insect’s vital organs, allowing the body to be used as an extension of its own.
The zombie ants, true to any Hollywood depiction, stumble clumsily – walking aimlessly and convulsing whilst the fungus continues to hijack its body. Once it is ready to produce reproductive spores, the mycelia threads penetrate the ant’s brain prudicing chemicals which alter the insect’s perception of pheromones. Then, with the fungus in full control, the ant is forced to wander from its nest and march to the site in which it will meet its pending fate.
On arrival, the hijacked host – nearing its demise – climbs a nearby plant, attaching itself to the top where the conditions are optimum for fungus growth. The unwelcome guest then devours the ant’s brain, killing its hapless host. These sites are mass graves, littered with the bodies of nest-mates that have previously succumbed to the fungus. And unfortunately for any inhabitant insects, specimens of the Cordyceps family can persist in the same location for years, growing steadily in numbers as ants continue to arrive, one after another, to die.
Although dead, this is not the end of the ant’s worth, as its empty exoskeleton acts as the perfect vessel for the fungus to complete its growth. Finally, the fully mature Cordyceps fungus – one of around 400 different ‘Zombie-producing’ species – disperses its spores as far and wide as possible to find its next unsuspecting victim, beginning the deadly cycle again. Whilst we live in a generation inundated with zombie horror stories, it is in nature where the undead are much more than just works of fiction.