Fig. 1

Axial profiles of intestinal pH, redox potential, and hydrogen partial pressure in the gut of litter-feeding cockroaches, determined with microsensors. Note that the gut axis has been normalized, i.e., the distances between the points of measurement are not absolute but instead represent cardinal points of each gut compartment (e.g., anterior, median, and posterior crop). In reality, the midgut region is considerably longer. Average length of the extended gut was estimated to be 84 mm (Byrsotria rothi), 46 mm (Ergaula capucina), and 33 mm (Pycnoscelus surinamensis) using a ruler. All microsensor measurements were made at the gut center; symbols indicate means with standard error of three guts