Regulation of pH in the digestive system of the cricket, Teleogryllus commodus Walker

Abstract

The physicochemical environment of insect digestive systems affects digestion because of its importance in both enzyme activity and its direct reducing potential. Although the regulation of lepidopteran midgut pH has been widely studied, nothing has been reported concerning the regulation of gut pH in Orthoptera. In this study we measured the pH of the crop, proventriculus, caeca, midgut and anterior hindgut of the cricket, Teleogryllus commodus Walker, to determine whether gut pH was regulated. pH of the crop was between 5.1 and 5.8 for crickets fed on a variety of diets, but was neutral in starved animals. In both starved and fed animals, the alimentary canal increased in pH incrementally between the crop and anterior hindgut, reaching pH 8–8.5 in the latter. Hæmolymph pH was slightly alkaline in fed animals (7.5) and acidic in starved animals (6.8). Transgut potential measurements and calculation of the equilibrium Nernst potential showed that the crop was not in equilibrium for H +, and we believe that this results from acidic secretions from the salivary glands. Neutralization of crop acid in fed and unfed animals resulted from anterior fluid movement, into the proventriculus in fed crickets and into the crop in starved individuals.