zombie-ant fungus
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What is the zombie-ant fungus?
The zombie-ant fungus, or Ophiocordyceps unilateralis, is a parasitic fungus that infects ants, primarily carpenter ants, and alters their behavior before killing them. The fungus begins as a spore on the forest floor that attaches to a passing ant. It then germinates, sending hyphae to breach the ant's exoskeleton.
Once inside, the fungus manipulates the ant, making it leave its nest and become unresponsive to external stimuli. The ant climbs a plant, locks its mandibles to attach itself, and dies. The fungus digests the ant from the inside out and erects a stalk from the antâs head, releasing spores to continue the cycle. Research suggests the fungus alters ant behavior by activating and suppressing certain ant genes.
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How does the zombie-ant fungus affect ants?
The zombie-ant fungus, Ophiocordyceps unilateralis, primarily infects carpenter ants by attaching sticky spores to the ant's body. Once inside, the fungus manipulates the ant's behavior, compelling it to leave its nest and walk along established trails. The fungus suppresses ant genes related to immune and stress responses, creating favorable conditions for itself. It directs the ant to climb a low-growing plant and lock its mandibles onto the vegetation, a behavior known as the "death grip". After the ant dies, the fungus digests the cadaver from the inside out and erects a stalk from the ant's head, releasing spores to continue its life cycle. Although fungal cells do not enter the ant's brain directly, the fungus secretes neuromodulatory agents that impair the chemical signals that allow the ant to communicate with its nestmates.
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Where is the zombie-ant fungus usually found?
The zombie-ant fungus (Ophiocordyceps unilateralis) is mainly found in pantropical regions and commonly infects carpenter ants. The fungus starts as a sticky spore on the forest floor and attaches itself to a passing carpenter ant. Once inside, the fungus manipulates the ant's behavior, causing it to leave its nest and eventually latch onto a low-growing plant. The location where the ant bites is specific to the ecosystem; for example, in warm temperate forests, infected ants are found attached to twigs, while in rainforests, they are found on the leaves.
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What happens to an ant once it is infected by the fungus?
Once a zombie-ant fungus infects an ant, the fungus manipulates the ant, inducing it to leave its nest and normal foraging behavior. The ant becomes unresponsive to external stimuli, and convulsions cause it to fall to the forest floor.
Triggered by the time of day, the ant climbs a plant, orients itself, and locks its mandibles to attach itself to the plant. This "death grip" is synchronized with the infection's extent, and death soon follows. The fungus consumes the ant from the inside out and finishes by erecting a stalk that releases spores from the antâs head. The fungus suppresses ant genes involved with immune- and stress-responses and secretes neuromodulatory agents.
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How does the fungus control the behavior of the ant?
The zombie-ant fungus (Ophiocordyceps unilateralis) infects carpenter ants and alters their behavior before killing them. After a spore attaches to an ant, it germinates and breaches the exoskeleton. The fungus then manipulates the ant, compelling it to leave its nest and normal foraging trails.
Infected ants become unresponsive to stimuli. The fungus induces convulsions, causing the ant to fall to the forest floor, where it climbs a plant, orients itself, and locks its mandibles onto the vegetation in a "death grip".
Research suggests the fungus alters ant behavior by activating and suppressing certain ant genes. It suppresses immune and stress response genes, and may affect genes involved in tryptophan metabolism, causing tremors and biting. The fungus also secretes neuromodulatory agents and toxins that impair chemical signals, further controlling the ant's actions.
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Why is the zombie-ant fungus important for scientists studying ecosystems and parasites?
The zombie-ant fungus is important to scientists studying ecosystems and parasites due to its unique ability to manipulate its host's behavior. Once inside the ant, the fungus directs it to leave its nest and attach itself to a plant in a location that favors fungal spore distribution.
Research into this fungus explores how it activates and suppresses certain ant genes to control behavior, suppresses immune responses, and secretes neuromodulatory agents. The fungus also contains bacteria-like toxins that may impair the ant's ability to communicate with its colony. By studying this interaction, scientists can gain insights into parasitic relationships and the mechanisms by which organisms can influence behavior within an ecosystem.
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zombie-ant fungus, (Ophiocordyceps unilateralis), species of parasitic fungus that infects ants and dramatically alters their behavior before killing them. The fungus is largely pantropical and primarily infects carpenter ants (genus Camponotus). Its taxonomy is contentious, with some research suggesting that each species of carpenter ant is infected by its own species of the fungus; it is treated here in the broadest sense (sensu lato). The zombie-ant fungus was formerly placed in the genus Cordyceps and is still often referred to simply as âcordyceps.â It does not infect humans.
- Kingdom: Fungi
- Phylum: Ascomycota
- Class: Sordariomycetes
- Order: Hypocreales
- Family: Ophiocordycipitaceae
- Genus: Ophiocordyceps
See also list of fungi.
Life cycle
The zombie-ant fungus begins its life cycle as a sticky spore on the forest floor. If the spore attaches to the body of a passing carpenter ant, it germinates infective hyphae (threadlike strands) to breach the insectâs exoskeleton. Once successfully inside the ant body, the fungus grows and manipulates the antâs behavior, eventually positioning the ant in a warm, humid location near the ground that will best serve to distribute a new crop of fungal spores. After the ant dies, the fungus finishes digesting the cadaver from the inside out and, as its final act, erects a triumphant stalk from the base of its conquestâs head. The stalk releases spores from characteristic lateral cushions, and the cycle continues.
âZombieâ behavior modification and mechanisms
The moniker âzombie-ant fungusâ arises from the organismâs uncanny manipulation of its host to generate a number of wholly novel behaviors, reminiscent of a zombie. Once the fungal mass inside an infected ant reaches a critical size (usually about 16â24 days following infection), the ant is induced to leave its nest at different times than its regular foraging habits, and it fails to walk along established ant trails. Infected ants are generally unresponsive to external stimuli, including other ants. Sporadic convulsions eventually make the ant fall from the tree canopy back to the forest floor, where its movements become seemingly nondirected and aimless. However, apparently triggered by the time of day, the moribund ant is soon directed to climb a low-growing plant, orient its body specifically on the vegetation, and permanently lock its mandibles to firmly attach itself to the plant. This âdeath gripâ is closely synchronized with the extent of infection and is the final act of the ant; death follows very shortly thereafter. The place of biting is characteristic to the ecosystem in which the infection takes place: infected ants in warm temperate forests are found mortally attached to twigs, while those in rainforests are found on the main veins or margins of leaves. Graveyards of dozens of infected ants, all with fungal stalks protruding from their bodies and anchored to leaves or twigs at roughly the same distance from the ground, are sometimes found and indicate just how precisely the fungus can control the dying behaviors of its victims.
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Research into the mechanisms behind the zombie-ant fungus suggests that the organism activates and suppresses certain ant genes throughout the infection to alter and control its behavior. For example, the fungus suppresses a number of ant genes that are likely involved with immune- and stress-responses, thus creating more favorable conditions within the insectâs body. Fungal cells are known to invade the muscle fibers of the hostâs body and may affect the expression of genes involved in tryptophan metabolism, causing the tremors and biting behavior. Although fungal cells do not seem to enter the ant brain directly, the fungus secretes a number of neuromodulatory agents, particularly guanobutyric acid and sphingosine, near both the central and peripheral nervous systems of its host. The fungus also contains a slew of unusual bacteria-like toxins, which may impair the chemical signals that allow the ant to communicate with other members of its nest.
Ant adaptations to limit infection
Carpenter ants in areas with zombie-ant fungus have evolved a number of adaptations to limit their exposure to the parasite. Carpenter ants in infested areas tend to be more arboreal than those without the fungus threat, suggesting that they avoid the forest floor to limit exposure to the spores. They also practice social grooming and can remove spores from each otherâs bodies before infection can occur. The ants have also been observed to carry infected members of the colony away from the nest and from their usual ant trails on the forest floor to reduce the spread of spores to high traffic areas, and they are known to actively avoid the graveyards of infected dead.
In popular culture
In popular culture, the zombie-ant fungus is the organism behind the human zombies in the video game and subsequent HBO show The Last of Us (2013; 2023â )âthe latter of which starred Pedro Pascal and Bella Ramseyâand the book and film, both written by M.R. Carey, The Girl with All the Gifts (2014; 2016).