Dicrocoelium dendriticum

Alas, the Internet connection at our apartment was down when I got home late last night, so my daily posting stride has been tripped up. :P (Not that it really matters.)

And now for a bizarre bit of biology. Last night my roommate Jack told me about Dicrocoelium dendriticum, also known as the Lancet liver fluke, which has the strangest life cycle. (Dave Barry disclaimer: I am not making this up.)

1. The parasite lives inside its host, often a cow.
2. The parasite mates.
3. Its eggs get excreted with the cow’s feces.
4. There’s a special kind of snail, Cionella lubrica (the terrestrial snail), which eats the cow’s feces.
5. The parasite’s larvae try to make their way out into the snail’s digestive tract.
6. The snail naturally has a problem with parasites chewing holes in its gut, so it puts them in cysts and drops them on the grass (kind of like those escape pods in Star Wars).
7. A special kind of ant comes along (Formica fusca), eating the slime of the snail.
8. The ant swallows a cyst, teeming with baby parasites.
9. One of these hundreds of parasites floats straight to some of the ant’s nerve cells and takes control of the ant’s actions. (Reminder: this is not science fiction.)
10. During the day the ant is normal, but at night (when the air is cooler) it climbs up to the top of a blade of grass and clamps down on it with its mandibles. It just chills there till morning, then becomes normal again.
11. Sometimes, though, a cow will come and eat the grass, getting infected with the parasite. See step 1.

How incredibly and unbelievably cool is that? Like something straight out of the movies, folks. But it’s real. The truth really is stranger than fiction sometimes.

I tell people about that parasite all the time. I had heard about it in 7th grade biology or something, and it really freaked me out. (But not anyone else I guess, but no one seemed to remember it.) I had actually begun to worry that I was making it up. Thank you for giving me at least a slight amount of assurance that I’m not going crazy.

I think you’re making this up.

I just feel bad for the cows.

I feel worse for the ants.

Humans can also get flukes and similar parasites by way of the same snails’ cysts. After drinking or swimming/bathing in contaminated water or eating plants or animals exposed to the cysts (water chestnuts, watercress, fish, crayfish, crabs) the cysts “hatch” if you will, and the parasite takes up residence in the human liver, lung tissue, or muscles and makes one quite sick. Perhaps the creepiest part is that they can migrate to other places in your body. Suddenly you have a large, sore bump on your arm and what’s under the skin? Parasitic worm. Also, but rarely, they can sneak into your brain and, well, kill you. But good news folks, they’re not endemic to the US.

Xister: I’d never ever heard of this before, but I’m glad someone else has. :)

Katherine: Just because I write fiction doesn’t mean everything I say is a lie. :P (Hey, that line works for prophets, too — just because they prophesy doesn’t mean everything they say is a prophecy. Huh.)

James: Me too, but at least they’re not lonely.

Ann: I wonder when the ants actually die — they’re small enough that they could easily avoid getting chewed, so maybe it’s the stomach acid that gets them? I don’t know.

e: Eek. I’ve heard horror stories (urban legends?) about people with bumps on their foreheads only to find out they’re spider eggs (hatching spider eggs) or flies or something. That just gives me horrid icky goosebumps. ~shudder~ (And yeah, having a worm get into your brain would be a bummer. Does the worm chew at it or what?)

Ben: Feeling sorry for the ants was only partially based on their deaths. I was thinking more about my worst nightmare: not being in control of my actions. Perhaps I’m projecting. There’s a great debate in the entomological world about how much intelligence insects have. But the way I understand it, the fluke only takes control of the ant’s motor impulses. That would mean the ant would still be feeling those natural instincts to be back with the colony yet wouldn’t be able to act on them. I imagine it would be frustrating to some extent, even to an ant.

I am so tempted to write a story based on all this… (Yes, I agree, it wouldn’t be a good feeling.)