Everybody knows the story. It shows up in a lot of sci-fi movies: a secondary character gets attacked by some sort of creature that latches onto their head and forces them to do its nefarious bidding. Well, as it turns out, this isn’t science fiction. Such phenomena are actually observed in nature (thus the lame “life-imitates-art” reference in the title). As it turns out, there actually exist a few species of insect and virus that alter (and sometimes control) the host’s brain. As a service to those warped-minded individuals (such as myself) who find this kind of thing fascinating, I present to you, dear reader, the List of the Most Disgusting and Interesting Parasites I Could Find:
AUTHOR’s NOTE: I take no responsibility for any vomiting or nightmares resulting from reading through this list…
- Emerald Cockroach Wasp (Ampulex compressa): This nasty little insect mounts the back of a cockroach, jabs its stinger through the back of the roach’s head, and using a precise set of sensors, guides the stinger, brain-surgeon-like, into the part of the cockroach’s brain that controls the escape reflex, injecting it with a venom. The wasp then — and this is the part that really blew me away — leads the now “zombified” cockroach around by the antenna, until they reach the wasp burrow, where they, in the standard fashion, lay an egg inside the cockroach, which eventually hatches, and the cockroach gets eaten from the inside out. As usual. Credit for the article upon which this bullet point is based goes to this site.
- Hairworm (Spinochorodes tellini): This was the first of the creepy brain-parasites I learned about. This diabolical little nematode enters a grasshopper’s body, and steadily grows until it occupies nearly all of the space within the grasshopper’s exoskeleton. Then, when it’s time for the worm to escape and mate — which it can only do in the water — it forces the cricket to drown itself in a puddle, thus freeing the hairworm to frolic and breed. You can learn more here.
- Rabies: All right, this one’s not as obscure as the others, but I still find it fascinating, in a macabre sort of way. I mean, rabies is practically the perfect parasite: it induces violent behavior in those infected by it, which leads to biting and scratching, which are the perfect methods of transmission of the virus! It’s hard to get much more direct than that. I’ve always though that a form of rabies that could spread more easily (perhaps even through mere close contact) would make a great basis for a horror film.
- The Ichneumon Wasp: This wasp is the creepiest, in terms of sheer gore. The female wasp stabs her ovipositor (that’s such a cool word…an ovipositor is basically a tube that a female insect uses to insert or deposit eggs) into a caterpillar, and injects some eggs. Before long, wasp larvae hatch and eat the caterpillar from the inside out. This, too, would probably make a good horror movie.
- Lancet Fluke (Dicrocoelium dendriticum): This fluke loves mammalian livers. In order to spread to a new liver, the parasites, excreted in the host’s feces, must be eaten by a snail. Then, when an ant drinks moisture from the snail’s trial (why it would do this is beyond me; snail slime is nasty), it becomes infected with juvenile flukes. These spread into the tiny little bundle of neurons the ant calls a brain (all right, it’s actually called a “ganglion” if you want to be specific). There, they lie in wait, controlling the host ant’s actions until nightfall, when they force the ant to climb a blade of grass, and latch on, waiting to be eaten by a liver-bearing herbivore. Creepy. Thanks to Carl Zimmer’s article The Return of the Puppet Masters for information about this one.
- Toxoplasma gondii: This nasty little parasite lives in cats, and spreads from cat to cat mainly via rats and other small mammals. The creepy thing is that, although otherwise normal-seeming, T. gondii-infected rats are completely unafraid of the smell of cats, a scent which normally terrifies them. Kind of makes you wonder: who among us might at this very moment be under the influence of…the parasites. Heh…silly idea…the parasites are our friends…the parasites want to help us…Hm…I don’t know what compelled me to write that… Credit for pretty much all of this bullet point also goes to Carl Zimmer.
I’ll amend this list if I run across any other interesting additions.