Parasite-host interactions have been honed over millions of years of evolution, achieving astonishing and sometimes unsettling precision. The variety of parasites capable of manipulating behavior ranges from viruses to insects and even worms. In some of the most intriguing cases, the parasite influences the host brain's neuronal circuits to control its cognitive functions. To maintain long-term behavioral manipulation, the parasite must secrete compounds that can alter gene expression with lasting effects. This allows parasites to hijack the host's decision-making and behavior. Mind-altering manipulation can occur in nearly all animals. However, the phenomenon is often studied in insects because of their simple nervous systems and goal-directed behavior. For example, when presented with two very similar concentrations of the same odor, fruit flies take longer to decide, which can lead to errors.
Suicide manipulation:
Fungal infection manipulates insect behavior. The fungus (Ophiocordyceps unilateralis) infects ants and feeds on their innards. It produces chemicals that alter the ants' navigation, compelling them to leave their nests and seek out a plant in a humid area to climb to its top. The ant then clamps its mandibles around a leaf or leaf stem—a behavior never seen in uninfected ants. The fungus consumes the ant's brain until it produces spores, killing the host. These spores burst and spread from the top of the tree to infect other ants, starting a new cycle.
In another example of parasitic infection, the Lancet liver fluke hijacks the ant's navigation by migrating to its head and settling near a cerebral ganglion. Unlike normal behavior, the infected ant climbs to the tip of a grass blade to be eaten by a grazing animal. The mature fluke expels eggs through the digestive system, infecting more ants.
Yet another case involves a hairworm, which needs water for reproduction. The hairworm infects crickets and other terrestrial insects, developing inside their bodies. When mature, it causes the insect to seek out water. When the insect falls into the water, the parasite emerges to reproduce.
Offspring Care:
Although solitary insects are not known to provide care and safety to their offspring, one of the parasites' most fascinating behaviors is to coerce a host into caring for the parasite's young. Developmental symbiosis occurs when individuals of one species cannot reach maturity without help from another species. For example, a wasp sting injects eggs into a caterpillar. The wasp larvae mature by feeding on the host and emerge after two weeks. However, one or two larvae remain inside the caterpillar. These siblings activate the caterpillar's muscles to violently move its upper body back and forth. This behavior protects the pupae by deterring predators.
The caterpillar's aggressive guarding behavior can also occur in other insects without parasites in their bodies. For example, a single wasp larva develops inside a ladybug, spinning a cocoon between its legs. The ladybug is still alive, but its nervous system triggers twitching and convoluted movements, which keep the wasp pupa safe from potential predators. It is thought that the parasite co-infects with a virus, which induces severe neuropathy and immune responses that cause the motor twitches.
Another example is the butterfly Maculinea arion, whose larvae mimic the smell of those of a particular ant species, causing its members to carry them into their nests, caring for them as their own. The sophistication and effectiveness of parasite infection might have inspired the
simulation hypothesis.
Infections in People
The fungal pathogen
Candida auris can cause bloodstream infections that can be fatal in 60% of cases. Toxoplasma infection can be linked to mood disorders and mental health issues, including
schizophrenia and behavioral changes, such as
promoting risky behaviors.
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Copyright © 2018 by Eva Deli
I enjoyed this read very much. Since I was already Well informed on the suicide manipulation technique that you've mentioned. This is amazing. Another demention to perceive life. Thank you for that.
ReplyDeleteHave a nice day and keep being your kind self.
Thank you for your kind feedback!
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