Figure 3. The effect of increased copper concentrations: (a) tap water control, (b) 50 mg/l copper as CuSO4, on the fluorescence intensity of hindgut, body, gills and Malphigian tubules of Chironomus luridus 4th instar larvae with and without tubes. Data are expressed as a mean percentage (± S.D.) relative to the fluorescence intensity of the midgut in each concentration.