- Esha Pradhan
Yes, Nature and the life it supports are beautiful. Yet, at times, (very) freakish as well.
To find sinister examples of mind control, you could turn to science-fiction; or, venture into a tropical jungle. Look beneath leaves that are at a height of around 25 centimeters. With luck, you might just find a carpenter ant (which belongs to the tribe Camponotini) with its jaws clamped tightly around the leaf’s central vein. It may look like it’s clinging on for dear life, but in reality, its time on Earth is already over. And its body belongs to a fungus, Ophiocordyceps unilateralis.
Spores of this fungus get attached to ants’ exoskeletons and eventually break through by mechanical pressure and enzymes. Initially, they exist as single cells in the bloodstream, where they reproduce via budding. At some point, they start working together by building short connecting tubes. In this way, they communicate and exchange nutrients among themselves, and eventually fuse into a single entity. They also start invading the ant’s muscles, either by entering the muscle cells themselves or occupying the spaces between them.
Surprisingly, the fungus does not invade the ant’s brain. It secretes a wide variety of chemicals that could influence the brain from outside, and/or exert direct control over the ant’s muscles. Once an infection is underway, the neurons in the ant’s body start to die. It is suspected that then, the fungus takes over its CNS – effectively cutting off the ant’s limbs from its brain and inserting itself in place, releasing chemicals that force muscles to contract and move.
Cycle showing symbiotic relationship between carpenter ant and O. unilateralis
Image credit -https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis#/media/File:Ant_behavioural_manipulation_by_O._unilateralis.png
An infected act exhibits irregular convulsions, which cause it to fall to the ground. Then, the fungus compels the ant to climb up a nearby plant stem to a height of approximately 25 centimeters above the forest floor – a zone that has precisely the right temperature and humidity for the fungus to grow. It forces the ant to lock its mandibles around a leaf’s vein. Once the ant is secured in place, muscle atrophy quickly sets in and soon, the ant dies. The fungus grows further, structurally fortifies the ant’s exoskeleton and secretes antimicrobials to ward off competition. Then, it sends a stalk through the ant’s pronotum (the dorsal section of the very beginning of the thorax), which grows into a bulbous fruiting body full of spores. And, because the ant typically ascends a plant close to its colony or the trails it forages along, the fungal spores rain down onto its sisters below.
The whole process takes approximately 4-10 days.
Ophiocordyceps unilateralis species display wide morphological variations, most likely due to the wide geographic range they are found in. Some variations may be a result of host-specific adaptation, i.e., specializations to have maximum effect on one particular ant species.
Image credit - https://commons.wikimedia.org/wiki/File:Schematic_drawing_of_Ophiocordyceps_unilateralis_morphology_on_an_infected_ant.png
The principal hosts of this fungus have also evolved certain behaviors that help reduce infection. They clean each other’s exoskeletons, and avoid the forest floor as much as possible. This is achieved by building nests high in the canopy, having a broad network of aerial trails, and descending to the ground only when canopy gaps are too large to cross. These methods are not observed in regions where the fungus is not present.
O. unilateralis is susceptible to an unidentified fungal infection itself, a mechanism by which its devastating impact on ant populations is limited. The hyperparasitoid moves in to attack as the fungal stalk emerges from the ant's body, reducing the viability of the spores.
Ophiocordyceps are known to be an important group in pharmaceuticals. They produce various known secondary metabolites, such as polyketides and naphthoquinone derivatives, as well as several structurally uncharacterized compounds. These natural products and their properties are being studied for their viability as anti-tumor, antimalarial, immunomodulatory, antibacterial agents and dyes.
For more, visit - https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis
Very informative!! 🔥
Highly insightful!