Table 2 The significant differences in fluorescence intensity (fluorescein penetration) between substrates (with silt tube or naked) and between larval body compartments of Chironomus luridus as a result of the exposure to different copper concentrations (2 way ANOVA).

Copper concentration   Degrees of freedom F - ratio P Significance level 50 mg/l Between substrates 1 48 0.0000 *** Between body compartments 4 3 0.028 * Interaction 4 0.38 0.82 n.s. 100 mg/l Between substrates 1 98.4 0.0000 *** Between body compartments 4 23.5 0.0000 n.s. Interaction 4 4.7 0.0032 **