Zombie Ants: How Parasitic Fungi Control Insects

Ophiocordyceps is a genus of parasitic fungi within the family Ophiocordycipitaceae, which is under the class Scotechiniaceae, under the phylum Ascomycota. This genus includes over 300 species that mainly target insects. In this article, we will focus on one particular species: Ophiocordyceps unilateralis. Also commonly known as the ‘zombie-ant fungus’, this fungus is known for manipulating the behaviour of its ant hosts, particularly carpenter ants, leading them to favourable locations for fungal reproduction.

How the Fungus Infect Ants

When an ant comes into contact with the fungus’ spores, the spores will attach on the ant’s exoskeleton and penetrate its body. The spores will grow inside the ant’s body, consuming the host's tissues while leaving the vital organs to keep it alive longer. After a few days, the fungus essentially hijacks the ant’s nervous system and takes over its physiological functions. (van Roosmalen & de Bekker, 2024)

It is believed that the fungus secretes specific proteins that play a role in manipulating the ant’s nervous system and behaviour. Furthermore, research has suggested that light may influence the biological rhythm between the fungus and the ant, further aiding in the manipulation process. (van Roosmalen & de Bekker, 2024)

How the Fungus Reproduce

Once the ant is infected, it will begin to exhibit altered behaviour, namely leaving its colony and climbing vegetation. The fungus will make its host climb about 25 centimetres above ground on a tree or plant, where the ant will then clamp firmly onto a leaf or twig; this grip is known as a ‘death grip’. This elevation is strategic as it ensures that the fungus can release its spores into the environment effectively to increase its chances of infecting more hosts. (van Roosmalen & de Bekker, 2024)

The fungus will continue to grow inside the ant’s body, until a stalk-like structure known as a fruiting body sprouts from the back of the ant’s head. This fruiting body is what releases the spores into the environment, and thus completing the life cycle of the fungus. (van Roosmalen & de Bekker, 2024)

The spore release mechanism is timed to coincide with environmental conditions that favour the spread of spores, such as high humidity and the presence of wind. Similarly to the elevated positive the fungus puts the ant in, the timing of spore release is crucial to maximise likelihood of spore dispersion and subsequent infection of ant hosts. (van Roosmalen & de Bekker, 2024)

Potential Applications of Ophiocordyceps

While Ophiocordyceps are generally known for their parasitic relationships with insects, a certain species known as Ophiocordyceps sinensis can lead to advances in biotechnology and pharmaceutical research due to its bioactive compounds and therapeutic properties.

Anticancer Applications: The β-D-glucan polysaccharide from Ophiocordyceps sinensis has shown potential to inhibit the growth of HepG2 liver cancer cells, with an IC50 of 511.79 µg/mL. Morphological studies have confirmed that the treated cancer cells exhibited apoptotic features, indicating potential therapeutic use in oncology. (Chatnarin, 2024)

Immunomodulatory and Anti-inflammatory Effects: The extracts of cultured Ophiocordyceps sinensis have exhibited anti-inflammatory effects and contain active compounds that inhibit NO and inflammatory cytokine production in microglial cells. (Fung & Ting, 2023)

Conclusion

The Ophiocordyceps fungus are nature’s real life zombie apocalypse, giving us a chilling reminder that nature far outmatches even the wildest human imagination. This fungal ability to control its host’s behaviour poses important questions about the principles of mind control in the natural world. Despite the terrifying concept, research on this fungus can provide valuable scientific insights.

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Article prepared by: Oan Yoong Ru, MBIOS R&D Associate 24/25

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References

1. Myconet. (n.d.). http://archive.fieldmuseum.org/myconet/outline.asp#classSord

2. van Roosmalen, E., & de Bekker, C. (2024). Mechanisms Underlying Ophiocordyceps Infection and Behavioral Manipulation of Ants: Unique or Ubiquitous? Annual Review of Microbiology. https://doi.org/10.1146/annurev-micro-041522-092522

3. Chatnarin, S. (2024). Potential of β-D-glucan polysaccharide from Ophiocordyceps sinensis OS8 cultivated mycelium on anticancer activity via inducing liver cancer cell death apoptosis. Process Biochemistry, 145, 243–249. https://doi.org/10.1016/j.procbio.2024.07.009

4. Fung, S. Y., & Ting, K. N. (2023). Biopharmaceutical Potential of Ophiocordyceps sinensis for Human Health (pp. 189–219). https://doi.org/10.1007/978-981-19-9550-7_6