Fig. 1. CLSM images showing accumulation of Texas Red in the lumen and/or cells of Malpighian tubules isolated from crickets (A–D), adult Drosophila (E) or larval Drosophila (F). The bathing saline (B), lumen (L) and cells (C) are indicated in each image. Tubules were bathed in 10 µmol l^–1 Texas Red for 15–30 min before each image was recorded. Tubule diameter is 60 µm in A–C and 35 µm in D,E. Panel B shows the fluorescence intensity profile from the base to the tip of the 110 µm-long arrow in A. Note the presence of large (C) or small (D) spherical concretions in the lumen of the cricket tubules. Some of the concretions in D appear to accumulate high concentrations of Texas Red and appear white whereas others are dark or opaque. The presence of large numbers of small intracellular concretions prevents clear distinction of luminal from cellular compartments in Drosophila tubules (E,F).