High-throughput fecundity measurements in Drosophila

Abstract

Fecundity is probably the most frequently studied fitness component in Drosophila. Nevertheless, currently used methods to measure fecundity are not well-suited for large-scale experiments, with many populations being assayed in parallel. Here we present a standardized pipeline to measure fecundity in many Drosophila population samples with substantially reduced hand on times. Using a high-contrast medium for egg laying, we developed a Java plug-in for ImageJ to quantify the number of eggs by image processing. We show that our method is fast and provides reliable egg counts.

Figure 1

Pipetting reliably transfers the targeted number of eggs. 72 pipetting trials, each aiming for 400 eggs were performed. Eggs were counted manually under a stereomicroscope. The box plot summarizes the entire experiment, while the gray diamonds indicate the egg counts for each trial.

Figure 2

Effect of agar concentration on the number of eggs laid. At each concentration, six replicated populations (grey diamonds) of 100 D. simulans each laying eggs for 12 hours and eggs were counted manually. Black bars depict medians. No significant difference in egg counts was detected between recipes at 2% and 3%, all other comparisons were significantly different at P < 0.05 (GLMM followed by Tukey’s HSD test, see main text for P-values).

Figure 3

Accuracy of the automated egg counting procedure. The number of eggs was measured for two populations of 100 D. simulans individuals for which fresh high-contrast medium plates were provided every 12 hours (i.e. a “transfer”). After each transfer, eggs were counted manually and automatically. Each population was replicated five times, and five transfers were made. The automated procedure provides reliable results similar to the manual counting (Spearman’s rank correlation, ρ = 0.934). The dashed line has a slope of one.