Utrecht University: Fungus that turns ants into zombies falls prey to other fungi itself
A fungus that turns ants into zombies sometimes becomes the victim of other fungal species itself. In papers in the scientific journals Functional Ecology and Persoonia, Utrecht University microbiologist Charissa de Bekker and international colleagues describe two previously unknown fungal species that master the zombie fungus.
When an ant of the species Camponotus floridanus becomes infected with the fungus Ophiocordyceps camponoti-floridani, its behavior changes. It leaves the nest, searches for a suitable patch of forest and crawls up, into the plants. Spurred on by the fungus, it climbs to a spot with just the right amount of sunlight. There, the ant bites into a plant and dies.
Then the fungus digests the ant. And when the time is right, a fungal fruiting body emerges from the ant’s body. From this mushroom-like structure, the fungal spores are spread.
They float with the wind and end up on the forest floor. A foraging, unsuspecting ant that picks up such a spore has a high chance of becoming the next zombie ant.
Strange fruiting bodies
How does the fungus manage to manipulate the ant’s behavior to its own advantage? Microbiologist De Bekker tries to find the answer to that question. De Bekker mainly focuses on the molecular biology of the system: which genes and proteins of the ant and the fungus play a role, and how do proteins produced by the fungus cause the ant’s behaviour to change?
Until recently, De Bekker worked in Florida, where the ants and the zombie fungus occur naturally. There, De Bekker and colleagues made a striking discovery: they found ants stuck to plants from which very strange fruiting bodies were growing. When the researchers delved further into this phenomenon, they concluded that those fruiting bodies were covered by another fungus. The fungus that turns the ants into zombies, thus sometimes suffers from a fungal infection itself.
Parasite of a parasite
De Bekker discovered that there are two different species of fungus that live on the zombie ant fungus. The fungus that uses the ants as a host really suffers from these two fungi: the ant manipulator fails to form a fruiting body more often when it is itself infected. That is why De Bekker describes the two new fungal species as hyperparasites: parasites that live off a parasite.
The two fungi were unknown to science. Because they are so different from all already known fungi, two new fungal genera have been called into existence. That also meant the researchers were allowed to come up with completely new scientific names for the microorganisms. One of the fungi was named Niveomyces coronatus. Niveo means “snowy”: ants with fruiting bodies affected by this fungus are covered by structures that resemble icicles covered with snow.
Further research in Utrecht
De Bekker recently returned to Utrecht University, where she did her PhD project several years ago. She brought the ants and fungi with her from Florida and keeps the whole system running in the lab.
In Utrecht, De Bekker will focus most of her research on what proteins are involved in the fungus’ manipulation of the ant. She also has plans to learn more about the hyperparasites. De Bekker: “With the changing climate, fungal diseases are becoming an increasing problem. Fungi adapt to the warmer earth, which means their optimal growth temperature is getting closer to our body temperature. We want to start looking at what proteins these previously unknown fungi use to attack the ant manipulator. This may eventually lead to the development of new drugs against fungal infections.”
Fascination
One of the reasons De Bekker started studying the zombie ant fungus, is that she became fascinated by images of insects infected by fungi years ago. De Bekker: “Infected insects are sometimes like works of art, sculptures. It makes me think about transience. In the end, we will all be eaten by fungi.”