Temperature effects on intra- and extracellular acid-base status in the American locust, Schistocerca nitens

This study examined the effect of temperature on hemolymph and intracellular acid-base status in the locust, Schistocerca nitens. Hemolymph pH decreased with temperature by 0.017 pH units·°C^-1 above 25°C, but was stable at lower temperatures. Average intracellular pH (pH_i, calculated from CO₂ distribution) decreased by approximately 0.018 pH units·°C^-1, in accordance with predictions for preservation of relative alkalinity and protein charge state. DMO was found to be unsuitable for use as an in vivo pH_i marker in locusts due to rapid metabolism and excretion of this compound. Hemolymph pH regulation when temperature changed was accomplished by a combination of variation of P_CO2 and [HCO₃^-], with changes in [HCO₃^-] predominating. Digestive tracts contained a large portion of total body water (over 30%), and total body CO₂ (over 40%). Variation in [HCO₃^-] may dominate pH regulation in locusts because of the relatively large size of the digestive tract and its powerful acid-base transporting capacities.