INTRODUCTION
On hearing the word zombies,our mind immediately flashes the images of horror films and science fictions where reanimated bodies are shown wandering mindlessly under some wrong influence. But if we talk about the natural world, the process of zombification is not just fictional rather it is a real phenomenon. Most of the parasitic species have evolved the ability to manipulate the behavior of their host which forces them to act in ways which benefit the life cycle of a parasite.
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In this blog post,we will expose the process of zombification, by quoting an example of a fungus named
Ophiocordyceps unilateralis which is often nicknamed as the "zombie-ant fungus". It is found in most of the tropical forests and it has developed an extraordinary ability to hijack an ant's body thus turning it into a vehicle for fungal reproduction. This phenomenon basically unfolds the parts of biology,horror story and an evolution.
THE LIFE CYCLE OF A ZOMBIE-ANT FUNGUS
The life cycle of a fungus is precisely efficient as well as quite chilling. Let's look into the details of its life cycle which are as follows:
●Spore Contact: The beginning of a zombie ant starts when a normal ant accidentally encounters fungal spores in its environment. These spores then attach themselves to the Exoskeleton of an ant and penetrate inside the body. Most of the infections remain localized but Ophiocordyceps spreads throughly in the internal tissues of an ant.
●Internal Spread: In the body of host,the fungus grows like a network of tiny threads,consuming only soft tissue so that the immediate death of an ant can be avoided. This allows the fungus to keep its host alive for a long period of time to complete its menacing and dark plan.
●Behavior Manipulation : After some days of infection,the ant starts behaving in a strange manner as instead of returning to its colony or foraging normally, it leaves its daily trail and climbs up the vegetation. Researchers have observed that an ant finds an optimal location which is usually above 25 cm above the forest floor as the temperature and humidity at that location are perfect for the growth of fungus.
●The 'Death Grip': Once an ant is in position, it clamps down on a leaf or twing with its powerful mandibles with a permanent grip. The ant cannot get released and it eventually dies locked in a place. This ruthless behavior ensures that the body of ant stays suspended in just the right conditions of temperature and humidity for the fungus.
●Fungal Growth and Spore release: After the host(ant) dies,the fungus consumes the remaining tissue and eventually produces a stalk which emerges from the head of an ant. This stalk release spores in the surrounding environment thus getting ready to infect the next generation of ants.
It can be clearly said that it is extraordinary survival strategy in which the fungus effectively programs its host to carry it to the perfect launching platform.
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>How does the Fungus controls the Behavior?
For a very long period of time,scientists have assumed that the fungus invades the brain of an ant and directly manipulated its neural circuits. But to our surprise,recent studies of research has changed this thought.
Studies which use advanced microscopy and molecular tools has revealed that the fungus avoids the brain entirely. Instead,it grows around the muscles and releases bioactive chemicals which affects how the ant's nervous system communicates with its body. Normally, we can say that fungus doesn't need to control the brain rather it hijack the hardware (muscles and nerves) instead of software (brain)
In the Pennsylvania State of University, researchers have discovered that during the 'zombie' phase,fungal genes get linked to secondary metabolites where specialized chemical are highly active. These compounds likely interfere with muscle contractions,circadian rhythms and even the sense of direction of an ant.
The result is that a living organism acts against its own will and turns into a puppet.
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SPECILIZATION IN EVOLUTION
The term specialization in evolution refers to the concept of 'One Fungus,One Host'.
As an example,we already know how Ophiocordyceps make ants their host and one of their fascinating aspects is that they adapt extreme specialization.
Each fungal species targets a specific insects. For example, the strain that can infect the carpenter ants cannot infect other species. This one-to-one relationship is a suggestion of a long evolutionary history in which fungus and host co-adapted over millions of years.
Infact scientists have categorized dozens of different Ophiocordyceps species each adapted towards its own specific host,from ants and cicadas to beetles and spiders.
One of the most precise examples of Parasitic Control in nature has been set by the evolutionary arms race between fungus and its specific host.
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ZOMBIE-MAKERS BEYOND FUNGI
The most famous example is of Ophiocordyceps ,however it is not the only parasite which is capable of turning creatures into zombies. Nature is full of organisms that manipulate their host in cunning ways which are as follows:
●Parasitic Wasps: Some of the wasps make caterpillars their egg laying station. The larvae hatch and feed on the host which releases chemicals that change the behavior of caterpillar. In some of the cases,the caterpillar behaves as a bodyguard which defends the developing wasps even if they consume it from inside.
●Hairworms(Nematomorphs): These parasites are known to infect crickets and grasshoppers. On reaching maturity,they require water for reproduction. The worm releases chemicals which compel the insect to jump in the water where the worm burst out to continue its life cycle.
●Toxoplasma Gondii: It is a single-celled parasite which infects rodents thus altering their behavior so they lose their natural fear of cats. This makes them an easier prey,which is exactly what the parasite wants because it can only reproduce inside a cat's digestive system.
These examples suggest that zombification is not a bizarre exception but a reccuring strategy in evolution. Controlling the behavior of a host is a powerful way for a parasite to complete its life cycle.
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WHY DO SCIENTISTS STUDY ZOMBIE PARASITES?
On an outside,researching about fungi which turn ants into zombies may seem like a niche pursuit,however it carries important implications across various fields of science which are as follows:
● It helps in understanding the evolutionary complexity by revealing sophisticated evolutionary adaptations that how can a fungus manipulates the body of organism.
● They are studied for knowing about their medical and pharmaceutical potential. The Ophiocordyceps species about which gained knowledge are used in Chinese medicine.
● They are used for pest control and agriculture as scientists are exploring ways by which parasites could naturally regulate the pest populations.