Fig. 5

Gut acidity after copper exposure is correlated with copper tolerance and is not linked to feeding behaviour. A Gut acidity results on the six RNA-sequenced strains after 24 h of copper treatment and 2 h of recovery (left) and after 24 h of control conditions and 2 h of recovery (right). Lower pH indicates that the dye turned yellow within the region of the gut containing copper cells; intermediate pH indicates that the dye turned green-brown, but a discrete acidic region could still be detected; higher pH indicates that the entire midgut was blue and the copper cell region could not be detected; and no feeding (clear or pale blue). For readability, chi-square test p-values comparing tolerant vs. sensitive strains are given in Additional file 11: Table S10. B Feeding avoidance in the presence of copper measured as a fold difference in consumption between treatment and control at 24 h (left) and 40 h (right) (see Additional file 11: Table S10). C Gut pH of the control strain w1118 (in brown) and the CG11594 deletion strain (in blue) after 16 h of copper treatment (left) and control conditions (right). An asterisk (*) indicates a difference across the treatment groups at p-value < 0.05 (*) and p-value < 0.01 (**). For all the plots, error bars represent the standard error of the mean of three biological replicates containing 28–44 females each (A and C) and the coefficient of variation of three control biological replicates containing 25–30 females each (B)