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The weird world of parasitoids

For the Bushwise students, the next few weeks represent the culmination of all of their hard work over the past four months. With their FGASA Level 1 assessments looming, the students are prepping for their chance to shine and show off their vast array of knowledge.

Part of that knowledge includes understanding the myriad of complex relationships between organisms in the ecosystem that hold the natural systems together. Perhaps one of the most fascinating relationships to be found on this planet is that of the parasitoids and their hosts.

A parasitoid is a parasite that eventually kills its host but only after it has served its purpose. That purpose? A living incubator. Here are a few examples of parasitoids that will make your skin crawl!

1. The Green Banded Broodsac (Leucochloridium paradoxum)


The adult broodsac lives inside the intestines of birds and upon mating, releases its eggs into the bird’s excretory system. Birds do not eat other bird’s droppings, but snails do – inadvertently consuming the eggs. The eggs than hatch in the snail’s stomach and slowly make their way to the head of the snail. Once here, the broodsac migrates into the eye stalks, swell up and pulsate.

The snail becomes a sitting duck with flashing green beacons on its head that resembles nice juicy caterpillars! The end result is inevitable. A passing bird gobbles up the free meal, inadvertently allowing the broodsac access to its digestive system for it to finish its life cycle!


2. The Horsehair Worm (Paragordius varius)


Hypnotism is not just reserved for the Las Vegas stage shows. Some horsehair worms have learnt the skill of mind control, and use it to deadly effect. Eggs hatch in water and after mating, the tiny larvae congregate around the water’s edge. Before long an insect such as a grasshopper or cricket will consume the larvae whilst quenching its thirst.

The larvae then ‘hypnotises’ the insect to make its way to water and to then commit suicide by jumping into the depths! Once drowned, the worm can wriggle free of its now defunct incubator and find a mate to repeat the process.


3. Phorid Fly


Phorid flies have been introduced to North America to try and control the spread of the fire ant. A female phorid fly injects an egg into the thorax of an ant and the ensuing maggot wriggles its way into the head where is quietly ingests the ant’s body fluid.

Once it has developed enough, the maggot releases a chemical which literally causes the membranes holding the ant’s body sections together to dissolve – causing the ant’s head to fall off.


4. Cordyceps fungi


There are numerous species of the Cordyceps fungi, each targeting a specific insect host. Perhaps the most famous is Ordiocordyceps unilateralis spore that infects the bullet ant of South America. The spore develops ‘tentacles’ known as mycelium that infiltrate the ant’s body via spiracles (breathing tubes).

Once nourished, the mycelium enters the brain, causing the ant to climb to a high point and clamp on to a piece of vegetation to await its fate. The fungus then consumes the protein rich brain before erupting from the ant’s head to release its spores!


5. Toxoplasma gondii


This single celled organism can only reproduce in the gut of a cat and the eggs are expelled in the cat’s scat. But how will a microscopic, limbless creature find its way into another cat? The answer lies in the cat’s favourite prey: rats and mice. Rats consume the feline scat and eggs, which soon hatch and journey to the brain. Once there, they interfere with the rat’s neural pathways, significantly lowering its inhibitions, basically rendering the rat fearless.

The outcome is that the rat becomes bolder and becomes easy prey for any a marauding cat. Mind control then can be conducted by even a single celled organism!


Bushwise offers comprehensive 50 and 23 week FGASA Professional Field Guide courses and Hospitality Internship Placements at Safari lodges in Southern Africa - a life altering experience and ideal platform for a successful career in the challenging and competitive ‘Big 5’ industry.


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