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How fungi manipulate their hosts

5.4.2023

Translation: Katherine Martin

Parasitic fungi infect insects, infiltrate their central nervous systems and eventually go on to manipulate their victims from afar – all in the name of evolution.

The creativity of evolution is sometimes expressed in ways ranging from weird to gruesome. It’s little wonder, then, that nature and its freakiest creatures are repeatedly used as inspiration for the plots of games, movies and series. Take The Last of Us, for example. In the acclaimed game adaptation, a fungus infects humans, causing them to mutate into zombies.

Remote-controlled zombie ants

As unrealistic as this scenario may sound, the world of fungi abounds with similarly grizzly examples. The creators of the Last of Us also drew inspiration from one of them, namely Ophiocordyceps unilateralis, which had already achieved some fame as the «zombie-ant fungus». And rightly so. The parasitic fungus infects ants and manipulates their behaviour in a creepy way.

But let’s start from the beginning. If an ant is unfortunate enough to crawl over the fungal spores of Ophiocordyceps unilateralis, its fate is sealed. Once the spores hit the ant’s body, its exoskeleton is dissolved by enzymes, allowing the fungus to grow inside the ant until it reaches the central nervous system. When it hits its target, the intruder takes control of the ant, which then starts behaving strangely – staggering, shaking and stumbling. Eventually the insect climbs up onto a plant, bites down hard on the underside of a leaf and dies.

What’s the point of this elaborate zombie-mutant plan?

It’s all down to evolution, with the fungi using the ant to reproduce and create ideal conditions for themselves. Once the ant has locked onto the leaf, the fungal hyphae infiltrate its entire body. After that, a fruiting body containing new spores grows out of the ant and starts the whole cycle all over again. In Thailand, where researchers have studied Ophiocordyceps unilateralis, the perfidious mechanism is actually so advanced that the ants take their final bite at high noon at a height of about 25 centimetres. This creates the perfect conditions for the fungus. Not only is it high enough for the ants not to be washed away during monsoon season, but it’s also humid and warm enough for more fungi to develop.

Entomophthora muscae manipulates houseflies

But Ophiocordyceps unilateralis isn’t the only horrifying fungus that nature has to offer. In fact, the zombie-ant fungus has met its match in the gruesomeness stakes in the form of Entomophthora muscae. Aptly named «insect destroyers», the fungi target houseflies, manipulating their behavior in much the same way as the zombie-ant fungi. It also infects its victims and forces them to relocate to a place suitable for the fungus to grow. The infected flies then spread their wings, allowing a network of fungal threads to grow throughout their bodies, which eventually go on to disperse even more spores.

Friend or foe?

More examples like these can be found in the fungal world, one being the cordyceps genus. Incidentally, Ophiocordyceps unilateralis would’ve been labelled as such under the old classification system. The tubular fungi parasitise their victims, control them from a distance, and eventually use them to spread their spores. In this case, the larvae or pupae of various insects are affected.

Cordyceps fungi were used in Chinese medicine as early as 1,500 years ago.
Source: Shutterstock

However, this very example demonstrates how versatile the world of fungi and their effects really are. While the names of the species I’ve described would inspire terror in insects, humans make good use of them. Cordyceps contains a variety of bioactive substances that have been used in Chinese medicine for more than 1,500 years. In this country, too, the dried mushrooms are now sold as a way of strengthening the immune system. In Chinese medicine, cordyceps is commonly used to increase the body’s energy, strengthen the immune system and lungs, support kidney function, regulate blood sugar and improve sexual function.

Careful, though: these fungi might not be able to control us à la The Last of Us, but they can trigger allergic reactions. With this in mind, always consult a doctor before attempting to harness the power of fungi for yourself.

The fungal world has plenty other exciting things to offer. Fancy reading more about its record-breaking feats, quirks or healing properties? Let me know in the comments.

Header image: Shutterstock

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Anna Sandner

Senior Editor

Anna.Sandner@galaxus.de

Science editor and biologist. I love animals and am fascinated by plants, their abilities and everything you can do with them. That's why my favourite place is always outside - somewhere in nature, preferably in my wild garden.

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