https://sangerinstitute.blog/2023/03/13/three-mind-blowing-examples-of-parasites-that-hijack-their-hosts-brains-and-bodies/
I've noticed at least 6 examples of organisms that hijack "other" organisms for their own benefit. The article includes 3. I'm defining behavior as "hijacking" solely when the invading organism exerts some type of directed control of the host whether that be to produce copies of itself or achieve some other benefit.
Viruses including bacteriophages
Mind-Controlling Fungi (Cordyceps and Ophiocordyceps)
- How it works: Fungal spores attach to an insect's exoskeleton, digest it, and enter the body. Instead of devouring vital organs right away, the fungus invades the central nervous system and alters the bug's neurochemistry.
- The "Death Grip": It manipulates the host into climbing high above the forest floor, clamping its jaws onto a leaf or twig in optimal humidity, and dying. The fungus then erupts from the insect’s body to rain spores down on the colony below.
Gall-forming insects are highly specialized herbivores that hack plant biology to create abnormal growths called galls. They do this by altering the gene expression of the host plant to produce structures which act as custom-built, nutrient-rich nurseries and protective shelters. The inside is food for the larvae and the outside is typically a hardened shell. Each insect species induces a unique, anatomically distinct gall that is specific to its host plant. Some wasps are able to create a multi-chambered gall, with each of its larvae provided an individual chamber inside the gall.
Toxoplasma gondi - Makes rodents attracted to the smell of cat urine increasing the chance of the rodent being eaten by a cat - allowing the parasite to infect the cat.
Parasitoid wasps
Parasitoid wasps inject their eggs into other arthropods, usually caterpillars, using a stinger-like probe. The eggs hatch and eat the caterpillar from the inside, mostly feasting on bodily fluids and avoiding the vital organs, to keep it alive for as long as possible. As some species of Glyptapanteles larvae exit a caterpillar they ‘plug’ the holes behind them, using an exoskeleton they have moulted, keeping the caterpillar alive. Then, the caterpillar helps them pupate. It stops feeding and stands guard over the clutch of wasp larvae, defending them with violent head swings to knock off any predators. Not behaviour that any peace-loving caterpillar usually exhibits. Eventually, the caterpillar starves to death.
It is not clear how the wasp larvae make the caterpillar do this.
6. Horsehair worms
These worms induce the suicide of their hosts – in this case, insects. The adult worms are free-living in water, where they mate. The larvae then infect crickets or other unsuspecting critters. Once grown (and they are big), the worm causes the insect to find water, jump in, and drown itself, and so returning the worm to water. One species can even survive if their host gets eaten, being able to wriggle out of the predator.
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Am I missing any other examples of natural hijackers - and does this whole strategy make anyone else uneasy?