Laura Smith
The Ophiocordyceps fungus, or the zombie ant fungus, is a parasitic fungus that infects and takes control of ants, causing them to act erratically and exhibit zombie-like behaviour. While the fungus does not physically invade the brain, it manipulates the ant's behaviour by interfering with its nervous system and controlling its muscles. Once the ant is locked in place, the fungus sends a long stalk through the ant's head, releasing spores and turning the corpse into a launchpad for infecting new ants. This process has been observed in various parts of the world, including the Amazon rainforest and Japan, and has inspired depictions in popular culture, such as video games and movies. So, while mushrooms themselves are not dead ants, they can grow out of dead ants and use them as a vehicle for reproduction and spreading their spores.
| Characteristics | Values |
|---|---|
| Common name | Zombie ant |
| Scientific name | Ophiocordyceps unilateralis |
| Type | Fungus |
| Genus | Ophiocordyceps |
| Species | More than 100 species |
| Hosts | Ants, beetles, caterpillars, cicadas, dragonflies, spiders |
| Mode of infection | Spores that attach and penetrate the exoskeleton |
| Manipulation | Behavioural manipulation, convulsions, climbing up plants, locking of jaw, controlling muscles |
| Location | Tropical forests, Japan, Americas |
| Media references | The X-Files, The Last of Us, Cult of the Lamb, Grounded by Obsidian Entertainment, The Girl With All the Gifts |
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What You'll Learn
The Ophiocordyceps unilateralis fungus
Ophiocordyceps unilateralis is found predominantly in tropical forest ecosystems, particularly in warm, humid environments that are ideal for its growth and reproduction. It has a wide geographic range, from Japan to the Americas. The fungus primarily targets ants from the tribe Camponotini, including carpenter ants (genus Camponotus). The life cycle of O. unilateralis includes and depends on the infection and manipulation of these ants. It first affects the ant's behaviour through convulsions, making it fall from its high canopy nest onto the forest floor. The fungus then controls the ant's movements, compelling it to climb up a plant and secure itself to a leaf vein with its mandibles, leaving distinctive dumbbell-shaped marks. The ants generally attach themselves at a height of 25-26 cm above the forest floor, on the northern side of the plant, in an environment with 94-95% humidity and temperatures between 20 and 30 °C.
Once the ant is locked in place, the fungus feeds on its victim's innards and slowly takes over its behaviour. After the ant dies, the fungus sends a reproductive structure, called the fruiting body, out through the base of the ant's head. This process takes 4-10 days. The fruiting body ruptures, releasing the fungus's spores, which then infect new ants. The dead ants are found in areas termed "graveyards", which contain high densities of dead ants previously infected by the same fungus.
O. unilateralis exhibits morphological variations that may be due to its ability to maximise its infection on specific host ant species. It has been found to infect multiple ant species, and researchers have identified over 200 species of Ophiocordyceps that can infect hosts from 10 insect orders, as well as spiders. Interestingly, O. unilateralis does not appear to invade the brain of its ant hosts. Instead, it may cast its mind control through bioactive compounds that interfere with the ant's nervous system and control the host's muscles directly.
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Fungi behaviour manipulation
Mushrooms are not dead ants, but they can be the result of fungi manipulating ant behaviour. Fungi have evolved a diverse array of strategies to manipulate arthropod behaviour, resulting in some of the most complex and impressive examples of behavioural manipulation by parasites.
One of the most famous fungi in the world is the "zombie ant fungus", which is a species of Ophiocordyceps unilateralis. This fungus takes over the mind of an ant, causing it to climb up a branch and bite onto the underside of a leaf before dying. The ant generally clamps to a leaf's vein at a height of 26 cm above the forest floor, on the northern side of the plant, in an environment with 94–95% humidity and temperatures between 20 and 30 °C (68 and 86 °F). Once the ant is dead, the fungus sends a mushroom-like fruiting body out through the base of the ant's head, turning its shrivelled corpse into a launchpad from which it can jettison its spores and infect new ants.
Ophiocordyceps unilateralis is found in tropical forests and infects a foraging ant through spores that attach and penetrate the exoskeleton. As the infection advances, the fungus compels the ant to leave its nest for a more humid microclimate that’s favourable to the fungus’s growth. The ant is then compelled to bite into a leaf vein on the north side of a plant, and wait for death. The changes in the behaviour of the infected ants are very specific, giving rise to the popular term "zombie ants". These behaviours are tuned for the benefit of the fungus in terms of its growth and transmission, thereby increasing its fitness.
In addition to ants, Ophiocordyceps infects other insects such as beetles, caterpillars, cicadas, and dragonflies. Researchers have also identified over 200 species of Ophiocordyceps that can infect spiders, though not all lead to behavioural manipulation. Fungi in the araneopathogenic genus Gibellula in the British Isles, for example, have been observed to infect orb-weaving cave spiders. While spiders are known to be hosts of fungal parasites, it is still largely unknown whether these infections result in behavioural manipulation.
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Hyperparasitism
Mushrooms are not dead ants, but rather a result of parasitic fungi that infect ants, most commonly the Ophiocordyceps unilateralis species, also known as the "zombie ant fungus". This fungus manipulates the behaviour of ants, causing them to climb vegetation and attach themselves to leaves or twigs before their death, earning them the nickname "zombie ants". The mushroom-like fruiting body of the fungus then sprouts from the dead ant's head, releasing spores to infect new hosts.
While Ophiocordyceps unilateralis is the most well-known species, there are over 100 species within the Ophiocordyceps genus that can infect various insects such as beetles, caterpillars, and dragonflies. Additionally, some ants have been found to be infected by multiple species of fungi simultaneously.
Among the various species of Ophiocordyceps, one particular fungus, O. unilateralis, stands out for its unique life cycle and ability to manipulate its host's behaviour. This fungus infects carpenter ants, specifically C. leonardi, and alters their behaviour to benefit its growth and transmission. The infected ants climb up plants and use their mandibles to secure themselves to leaf veins at a specific height and humidity level. After the ant's death, the fungus sends out a fruiting body through the ant's head, releasing spores to infect new hosts.
Ophiocordyceps unilateralis has gained notoriety for its "zombie ant" behaviour and has inspired various forms of media, including video games and television shows. However, it is important to note that not all species within the Ophiocordyceps genus lead to behavioural manipulation of their hosts.
Now, let's shift our focus to the concept of hyperparasitism in the context of mushrooms and ants. Hyperparasitism is a phenomenon where a parasite becomes infected by another parasite. In the case of Ophiocordyceps unilateralis, it has been observed that this fungus can be parasitized by other fungi species, specifically O. sessilis and O. pulvinata. This behaviour is not uncommon among cordyceps fungi, as they frequently switch hosts between insects and other fungi. Additionally, O. unilateralis has its own parasitic fungi, known as hyperparasites, which include species such as Niveomyces coronatus and Torrubiellomyces zombiae. These hyperparasites may play a regulatory role, preventing O. unilateralis from becoming too lethal to its ant hosts and ensuring the fungus's survival.
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How ants can avoid being zombified
The Ophiocordyceps unilateralis, also known as the zombie ant fungus, is a parasitic fungus that infects carpenter ants, principally C. leonardi. The fungus infects a foraging ant through spores that attach and penetrate the exoskeleton and slowly takes over its behaviour. The Ophiocordyceps genus includes more than 100 species, and researchers have identified over 200 species of Ophiocordyceps that can infect hosts from 10 insect orders, as well as spiders.
Ants can avoid being zombified by the zombie ant fungus in several ways:
- Ants can avoid areas where the zombie ant fungus is present. For example, in areas where O. unilateralis is found, C. leonardi builds its nests high in the canopy and creates a broad network of aerial trails that only occasionally move down to the ground level, reducing the risk of infection.
- Ants can also sense when a member of their colony is infected and carry the infected individual away from the colony to prevent the spread of the fungus.
- Ants typically have social immunity, where sick members are kicked out of the group to prevent the rest from getting sick.
- Ants also groom and clean each other's exoskeletons to decrease the presence of spores attached to their bodies.
- In some cases, hyperparasitism may occur, where a parasite is infected by another parasite. This can limit the viability of infectious spores and help keep the zombie ant fungus in check.
While these methods may help reduce the risk of infection, it is important to note that the zombie ant fungus has evolved to infect ants for millions of years, and it is challenging to completely avoid being zombified.
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The life cycle of Ophiocordyceps
Ophiocordyceps unilateralis, also known as the "zombie-ant fungus", is a parasitic fungus that infects and alters the behaviour of ants before killing them. The fungus is largely pantropical and primarily infects carpenter ants of the genus Camponotus.
After the ant has died, the fungus sends a fruiting body out through the base of the ant's head, turning its shrivelled corpse into a launchpad from which it can jettison its spores and infect new ants. The spores are released 4–10 days after the fungus is ready to reproduce. The dead ants are found in areas with high densities of other dead ants previously infected by the same fungus, known as "graveyards".
Ophiocordyceps unilateralis exhibits morphological variations due to its wide geographic range, from Japan to the Americas. It has been hypothesized that these variations may also be a result of maximizing its infection on a specific host ant species. The O. unilateralis core clade has distinct morphological characteristics, including a single stroma with a Hirsutella asexual morph that arises from the dorsal neck region of the dead ant and produces a dark brown perithecia attached to its stalk.
Ophiocordyceps is a genus of fungi that includes over 100 species, many of which infect various insects such as beetles, caterpillars, cicadas, and dragonflies. Some Ophiocordyceps species inhabit Japanese cicadas and may have replaced symbiotic bacteria to help their hosts process nutrients from sap.
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Frequently asked questions
No, mushrooms are fungi that can infect and grow on dead ants, but they are not ants themselves.
The scientific name of the zombie ant fungus is Ophiocordyceps, and it has many species that infect different insects.
The fungus starts as a spore that attaches to an ant's exoskeleton and penetrates it. It then grows through the ant's body, feeding on its innards and hijacking its nervous system to control its behaviour.
The fungus manipulates the ant to climb up a plant stem and lock its mandibles around a leaf vein at a specific height above the ground. After the ant dies, the fungus sends a fruiting body out through the ant's head to release its spores and infect new ants.
