A More Standardized Method for Imaging and Measuring Drosophila Thorax Length Using ImageJ

Thorax measurements are important metrics of Drosophila fitness and are often correlated with key life history traits such as lifespan and fecundity. Therefore, thorax length is a widely used measure in studies of genetic variation and plasticity in response to environmental alterations. However, the lack of fixed landmarks means that thorax measurements can sometimes be inconsistent and highly variable. Here we outline a dorsal bristle-guided method of thorax measurements, which we could use to draw a reliable and repeatable line from the thorax scutellum to the anterior thorax edge. We analyzed and compared this bristle-guided marker method to a non-landmark based thorax measurement, in a set of measures of female and male D. melanogaster. We found that the bristle-guided method exhibited significantly less variation between technical replicates than did the non-landmark based measure.