Drosophila is a powerful model organism with rapidly evolving genetic tools. So much so that the technical advancements made by many Drosophila geneticists and neurobiologists over the last several years, which have enabled us to temporally manipulate the expression of genes in specific brain regions or to alter the excitatory properties of individual neurons, completely outpaced advancements in behavioral assays.
Measurement of fly feeding behavior is one area that is overdue for improvement.Have you ever struggled with preparing flies for the proboscis extension reflex assay and wished that you could measure flies' appetitive feeding response in a non-invasive and high-throughput manner?
Have you ever scored blue, red, and purple-bellied flies for food preference assay and realized the ambiguity between bluish-purple and reddish-purple? Have you realized that there is a lot of individual variability in food choices?
Have you ever done 30min-time course capillary tube feeding assay for 6hrs and wished that you could manage a larger sample size for each time point?
These were few of my honest realizations that I experienced while I was struggling to perform feeding assays in flies over the last three years. In the end, I decided that no matter how experienced I became in each one, there would be no way to improve my results; all of the existing techniques had critical limitations that would hinder me from getting the right answer to my research questions. So I went back to the drawing board to design my own dream apparatus that could solve most of the problems.
While discussing all my "wishes" for a fly feeding assay with colleagues and mentors, Scott and Zach with their skills in machinery, electronics, and software development came on board to create what ultimately became the FLIC (Fly Liquid-food Interaction Counter)!
The FLIC is a complete hardware and software system for collecting and quantifying continuous measures of feeding behaviors in Drosophila. Here are some of its highlights:
- One can continuously observe fly's feeding behavior in an undisturbed environment because the system detects analog electronic signals every time a fly makes physical contact with liquid food. Once the experiments is set up, there is no further operator involvement.
- Is a fly tasting or feeding? Are tasting events followed by feeding events? The signal characteristics in the FLIC allow one to distinguish between feeding and tasting.
- Continuous measures allow one to examine time-dependent feeding and food choice, allowing one to bring an important temporal dimension to cutting edge research questions.