BIOEB101 Essay: The Fascinating World of Parasitic Mind Control

This essay explores the phenomenon of parasitic mind control, focusing on how parasites manipulate the behavior of their hosts to enhance their own reproductive success. The essay primarily discusses the interaction between the parasitic fungus Ophiocordyceps unilateralis and its host, the carpenter ant Camponotus leonardi, detailing how the fungus alters the ant's behavior, leading to its demise and the fungus's spore dispersal. It further examines a similar interaction involving the parasitic caterpillar Narathura japonica and its host ant Pristomyrmex punctatus, highlighting the manipulation of the ant's behavior through chemical secretions. The essay also touches upon the evolutionary arms race between parasites and hosts and concludes by emphasizing the manipulative strategies employed by parasites to control their hosts' cognitive functions and the resulting impacts on the host organisms. The essay references several scientific studies to support its claims, including Hughes et al. (2011) and Hojo et al. (2015).

Running head: PARASITIC MIND CONTROL
Parasitic mind control
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PARASITIC MIND CONTROL 1
Introduction
Parasitism is the structural adaptation of some organisms to live or depend on
the mechanisms of another organism, causing the host organism some harm.
Parasites possess the ability to control the behavioural activities of their hosts
in their personal favours, which has gained significant interest of scientists.
This paper discusses the manipulation of parasitic fungi, Ophiocordyceps
unilateralis on its host ants, Camponotus leonardi. This interaction is
supported by another example of a similar interaction between the parasitic
lycaenid butterflies, Narathura japonica and their effects on the host ants,
Pristomyrmex punctatus.
Discussion
A study conducted by Hughes et al. (2011) demonstrates that some parasitic
fungi such as the Ophiocordyceps unilateralisalter the navigational system of
their ant hosts, Camponotus leonardi. These fungi secrete transmitters that can
alter the navigational processing of the host ant species of Camponotus
leonardi. The fungi begin the infection by attaching its spores to the cuticle of
the host ants. These attached spores germinate on the body of the host ant and
break into the system of the host through the host trachea. The mycelia of the
parasitic fungi grow and develop inside the system of the ant by feeding on the
internal organs of the ant except for the vital organs. Subsequently, the fungi
release some unidentified substances into the ant’s system which controls the
navigational behaviour of the host ants causing the host ant to move towards
the apical parts of a plant or a tree and clamp to the tip of one of the leaves

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with the help of its mandibles. This behaviour of the host ants in not observed
in the absence of the parasitic infection by Ophiocordyceps sp. Meanwhile, the
fungus engages itself in the production of its spores. After the production of a
significant number of spores, the fungus ultimately ingests the brain of the ant,
thereby killing it. Within three days of the host ant’s death, post-mortem
growth of the fungus begins by emanating enormous hyphae from the
membranes of segments and stalk formation at the back of the host’s head.
These air-borne capsules discharge the spores on their descent, distributing the
spores to the environment. These spores again, infect the host ants and hence,
the cycle of infection is repeated.
In the interactivity between the parasitic fungi Ophiocordyceps sp. and its host
ant Camponotus leonardi, the manipulation of the parasite-induced suicidal
behaviour in the host ant and costs the host ant its life. In contrast, the fungal
parasite O. unilateralis benefits from the interaction utilizing the host ant’s
mechanisms for its metabolism and moving the host ant towards the optimum
conditions of light and humidity required for the germination of the fungal
spores (Libersat, Kaiser & Emanuel, 2018).
Camponotus leonardi, the principal host of O. unilateralis has provided
evidence of adaptive behaviours to control the fungal infection by limiting the
contact with the forest floor as a defence mechanism against the fungal
parasites. Moreover, in the regions of existence of O. unilateralis, the host and
sets up a high, elevated nest in the canopy, and increases its network of aerial
trails. However, often the ant trails have to descend to the forest floors as the
gaps of the canopies are difficult to cross. On descending to the forest floor,

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the ants minimize the lengths of their trails to below five metres as an
additional defence to avoid fungal infections (Andersen et al., 2012).
An example of this behavioural control of insects can be explained by a
similar interaction between the parasitic caterpillar Narathura japonica and its
host ant Pristomyrmex punctatus. This interaction between the caterpillar and
the host ant appears as a symbiotic relationship on the surface, where both the
organisms benefit from the interaction. However, careful observation of the
interaction reveals that the attendant ants are infected by the parasitic
caterpillars, increasing the aggression in the ants. The infection begins with
the secretion of a sugar-rich substance in the caterpillar, which manipulates the
locomotory behaviours of the host ant. Moreover, these secretions have also
been noted with reduced the levels of dopamine in the brains of the ants. The
caterpillars secrete the chemicals from its dorsal nectary organ (DNO), which
is consumed by the host ants. The intake of these DNO secretions alters the
dopaminergic regulation in the host ants to increase partner fidelity. The
aggressive responses are observed on everting the tentacles of the parasite
caterpillar. It is also observed that the ants also tend to attach to the caterpillars
whose tentacle organs have been removed experimentally suggesting that the
DNO secretions are more than just nutritional means but also contains
chemicals to alter the behaviour of the attendant ant (Hojo et al., 2015).
The potential benefits of the parasitic caterpillar Narathura japonica by
keeping its host ant Pristomyrmex punctatus is offspring care. The caterpillar
reduces the locomotory behaviour of the host ant to protect the larvae from
predators. In the process, the cognitive ability of the ant reduces to a large
extent and results in the dependency of the host ant on the parasitic caterpillar.

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It is also observed that in some cases the host ant fails to live independently in
an environment without the tentacle organ of the parasite.
The interaction between the Pristomyrmex punctatus and its parasite
caterpillar Narathura japonica has led to some evolution in the recognition
pattern of the host ants to differentiate a mutualistic relationship with the
caterpillars with beneficial nutritional rewards from the parasitic species of the
caterpillars secreting artificial food rewards. This recognition is based on
chemical signals specific to their partners. The evolution of these signals is
largely dependent on the cognitive abilities of the host ant to recognize the
hydrocarbon profiles of the DNO secretions (Hojo et al., 2014).
The evolutionary arms race (EAR) may be defined as a competition, which
resembles an arms race among the collections of co-evolving traits, genes or
species for developing adaptations and counter-adaptations in opposition to
each other. Often, it serves as positive feedback. Each of the organisms in the
EAR is persistent in adapting themselves to compete with each other, which
results in an increasingly complex interaction between the two (Małagocka et
al., 2019). The most remarkable example of this is the zombie ants and its
parasitic fungal species. It is represented in the precision of the fungus to
position the host ant exactly 25 cm above the forest floor on the north-north-
western leaf of the plan where the wind speed is low and the sunlight and
humidity are optimum for fungal reproduction (Andriolli et al., 2019). In
response, the carpenter ants have also evolved themselves by building high-
reaching nests to avoid fungal infections. This example exhibits the complex
interactions involved in the evolutionary arms race.

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Conclusion
In conclusion, parasites direct the behaviours of their hosts by manipulative
their cognitive functioning with the help of their extended phenotypes and
harms or ultimately kills the host organism. The case study of the interaction
of Ophiocordyceps unilateralis fungi with its host ant Camponotus leonardi
demonstrates one such ability of the insects to control the minds of their hosts.
The parasitic fungus can extend the phenotypic nature of the ants through
fungal secretions to manipulate the ants into providing an optimum
reproductive environment beneficial for fungal replication. Similarly, the
example of the interaction between the Narathura japonica caterpillars with
their host ants Pristomyrmex punctatus represents another complex example of
behavioural alteration of the host ant to protect the caterpillar from external
predators by reducing their locomotory behaviours.

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References
Andersen, S. B., Ferrari, M., Evans, H. C., Elliot, S. L., Boomsma, J. J., &
Hughes, D. P. (2012). Disease dynamics in a specialized parasite of ant
societies. PloS one, 7(5). 10.1371/journal.pone.0036352
Andriolli, F. S., Ishikawa, N. K., Vargas-Isla, R., Cabral, T. S., de Bekker, C.,
& Baccaro, F. B. (2019). Do zombie ant fungi turn their hosts into light
seekers?. Behavioral Ecology, 30(3), 609-616. 10.1093/beheco/ary198
Hojo, M. K., Pierce, N. E., & Tsuji, K. (2015). Lycaenid caterpillar secretions
manipulate attendant ant behavior. Current Biology, 25(17), 2260-
2264. https://doi.org/10.1016/j.cub.2015.07.016
Hojo, M. K., Yamamoto, A., Akino, T., Tsuji, K., & Yamaoka, R. (2014).
Ants use partner specific odors to learn to recognize a mutualistic
partner. PLoS one, 9(1). 10.1371/journal.pone.0086054
Hughes, D. P., Andersen, S. B., Hywel-Jones, N. L., Himaman, W., Billen, J.,
& Boomsma, J. J. (2011). Behavioral mechanisms and morphological
symptoms of zombie ants dying from fungal infection. BMC
ecology, 11(1), 13. https://doi.org/10.1186/1472-6785-11-13
Libersat, F., Kaiser, M., & Emanuel, S. (2018). Mind control: how parasites
manipulate cognitive functions in their insect hosts. Frontiers in
psychology, 9, 572. 10.3389/fpsyg.2018.00572
Małagocka, J., Eilenberg, J., & Jensen, A. B. (2019). Social immunity
behaviour among ants infected by specialist and generalist

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fungi. Current opinion in insect science.
https://doi.org/10.1016/j.cois.2019.05.001