Fig. 6. Larval Cu distribution. Third instar larvae were raised under Cu-limited conditions with 100 µmol l^–1 BCS (A,B), basal food (C,D and enlarged in E,F, respectively) or exposed to 1 mmol l^–1 Cu for 4 h (G,H) and then dissected. MtnA-EYFP fluorescence was used as a proxy marker of Cu distribution in w¹¹¹⁸ control larvae (A,C,E,G) and Mvl^97f/+ larvae (B,D,F,H). EYFP levels were not different between male and female larvae (data not shown). Regions of the gut are identified in C: pv, proventriculus; gc, gastric caecum; am, anterior midgut; cc, copper cell region; mm, middle midgut; fe, iron cell region; pm, posterior midgut; mp, Malpighian tubule. Under basal conditions, control larvae (C) showed a complex distribution of EYFP throughout the anterior, middle and posterior midgut as well as the proventriculus and Malpighian tubules. By contrast, Mvl^97f/+ larvae (D) did not show the same high levels of EYFP in the proventriculus and anterior midgut (clearly seen in the enlargements E and F). Under Cu-limited conditions, EYFP levels were reduced across all tissues of both control (A) and Mvl^97f/+ (B) larvae, with the exception of the iron cell region of the middle midgut and in the imaginal ring at the midgut–hindgut border (indicated by arrows in A). Under Cu-excess conditions EYFP levels were saturated in all tissues of both control (G) and Mvl^97f/+ (H) larvae.