Quantifying Drosophila food intake: comparative analysis of current methodology.

Food intake is a fundamental parameter in animal studies. Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism. Here, we compare several common Drosophila feeding assays: the capillary feeder (CAFE), food labeling with a radioactive tracer or colorimetric dye and observations of proboscis extension (PE). We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish. We conclude that performing the radiolabeling and CAFE assays in parallel is currently the best approach for quantifying Drosophila food intake. Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.