Measuring O₂ Consumption in Drosophila melanogaster Using Coulometric Microrespirometry

Coulometric microrespirometry is a straightforward, inexpensive method for measuring the O₂ consumption of small organisms while maintaining a stable environment. A coulometric microrespirometer consists of an airtight chamber in which O₂ is consumed and the CO₂ produced by the organism is removed by an absorbent medium. The resulting pressure decrease triggers electrolytic O₂ production, and the amount of O₂ produced is measured by recording the amount of charge used to generate it. In the present study, the method has been adapted to Drosophila melanogaster tested in small groups, with the sensitivity of the apparatus and the environmental conditions optimized for high stability. The amount of O₂ consumed by wildtype flies in this apparatus is consistent with that measured by previous studies. Mass-specific O₂ consumption by CASK mutants, which are smaller and known to be less active, was not different from congenic controls. However, the small size of CASK mutants resulted in a significant reduction in O₂ consumption on a per-fly basis. Therefore, the microrespirometer is capable of measuring O₂ consumption in D. melanogaster, can distinguish modest differences between genotypes, and adds a versatile tool for measuring metabolic rates.