Video 1. The video (3:35 minutes at four times accelerated speed) shows a typical experiment with an isolated and perfused anterior midgut of larval A. aegypti. Luminal solution: low buffer mosquito saline with m-cresol purple (0.04%). Hemolymph-side solution: high buffer mosquito saline with serotonin (0.2 μmol l⁻¹). The posterior part of the preparation is tied with a human hair onto a perfusion pipette (left) and a glass rod inserted into the lumen (right) maintains the tissue in the focus of the microscope. Luminal perfusion was stopped at the beginning of the video. The color change of m-cresol purple that reflects alkalinization (from yellow to purple) begins at the anterior end of the midgut (right) and continues towards more posterior regions of the anterior midgut (left). The peristaltic muscular activity can also be easily observed (cf. Onken et al. 2004b). At 2:40 minutes, the perfusion pump is started again and the purple, alkaline solution is flushed from the lumen of the preparation.