Figure 2. Effect of Chironomus luridus 4th instar larvae exposure (within and without tubes) to different copper concentrations, on the permeability of fluorescein into (a) midgut, (b) hindgut, (c) body, (d) gills, (e) Malpighian tubules. The data are expressed as fluorescence intensity, mean a.u.± S.D. Larvae with silt tubes were exposed to copper and FLU while within the tubes.