So, Basically, I Keep Fruit Flies Alive Until the Appropriate Time to Kill Them. Poor Things. by Cailean Cavanaugh

I’m Cailean Cavanaugh, 17, a rising senior at William Tennent High School, and, as you might imagine, a member of the TRIP initiative. Some boring personal details: I’m interested in math and science, but I’m also a musician (bass and saxophone), history nerd, short story writer, robotics team member, artist, professional amateur photographer, and avid Dungeons and Dragons fan. None of that matters now, though, at least not until I find a way to apply one or more of my other interests to the fruit fly experiments that TRIP is all about. I’m looking for ways to do that right now, and just you wait until I write a dungeons and dragons campaign based on my experiences here!

I’m looking forward to learning as much as I can about fruit flies, conducting independent research, and getting to know what it’s like to work in a lab. I will do all this while trying to avoid accidentally killing dozens of fruit flies through excessive CO2 exposure in order to intentionally kill them later to perform a microbiome assay and measure the effects of senna and sugar intake on the flies’ gut bacteria...

That was a lot, so let me properly break down my first experiment in a format easier to make sense of than a confusing run-on sentence. I put 60 unsuspecting flies (30 male and 30 female) into four separate vials, and will expose each one to different conditions. One vial is a control; the flies eat their normal food. The second vial was given high-sugar food. The third vial was given a laxative herb called senna, while the fourth vial was given high sugar food and senna. On the next class day, I will perform a microbiome assay in order to determine what effects (if any) the high-sugar food and senna had on the flies’ microbiome. Unfortunately, this will require killing the flies.

Even though the flies will eventually need to die, they need to be kept alive long enough that any effects of them eating altered food become noticeable. This presents several problems, the most immediate of which is how to transfer the flies between vials. As you probably know, flies fly, so we can’t just dump one vial into another without getting flies everywhere and making Dr. Purdy wonder why she ever let us past the interview. 

The solution to this is to knock out flies by using a CO2 gun to fill their vials with carbon dioxide, then move them to a small pad where they are kept unconscious with yet more carbon dioxide. This also provides a convenient location to sort the males from females to keep the experimental vials balanced between sexes—an all-male vial would provide poor experimental data and make too many depressed fruit flies. There’s a catch, though. CO2 can be harmful to the flies, and they can die if left on the CO2 pad for more than 20 minutes. This goes against my stated mission of keeping them alive until the proper time to kill them, so I naturally had to sort them quickly. ​

Stay tuned to hear more about the exciting world of flies’ gut bacteria! It’s a blast, I assure you.