REGULATION OF PH IN THE DIGESTIVE-SYSTEM OF THE CRICKET, TELEOGRYLLUS-COMMODUS WALKER

The physicochemical environment of insect digestive systems affects di gestion because of its importance in both enzyme activity and its dire ct reducing potential, Although the regulation of lepidopteran midgut pH has been widely studied, nothing has been reported concerning the r egulation of gut pH in Orthoptera, In this study we measured the pH of the crop, proventriculus, caeca, midgut and anterior hindgut of the c ricket, 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 starve d and fed animals, the alimentary canal increased in pH incrementally between the crop and anterior hindgut, reaching pH 8-8.5 in the latter , Haemolymph pH was slightly alkaline in fed animals (7.5) and acidic in starved animals (6.8), Transgut potential measurements and calculat ion of the equilibrium Nernst potential showed that the crop was not i n equilibrium for H+, and we believe that this results from acidic sec retions from the salivary glands, Neutralization of crop acid in fed a nd unfed animals resulted from anterior fluid movement, into the prove ntriculus in fed crickets and into the crop in starved individuals. (C ) 1997 Elsevier Science Ltd.