干旱区生态环境知识资源中心

A number of physiological systems have the potential to participate in extracellular acid-base regulation in insects. Results from several studies suggest that, in locusts, the ventilatory system is the major participant in hemolymph pH regulation when the acid-base challenge is characterized by a rise in hemolymph Pco(2). While the renal system has been shown to secrete actively both titratable acid and ammonium, no major role of the excretory system in hemolymph pH regulation has yet been demonstrated We report here that starved locusts (Taeniopoda eques) excrete net acid in the form of titratable acid and ammonium. In contrast, T. eques fed on Romaine lettuce excrete titratable base and have higher rates of bicarbonate excretion, which results in net base excretion. Nitrogen excretion rates (ammonium and total urate) do not differ between fed and unfed groups. This is the first report of flexible titratable acid-base excretion in insects in vivo. The results are consistent with in vitro studies that report that hormonal factors believed to be elevated during feeding increase water and ion reabsorption and decrease titratable acid secretion by the hindgut. The excretory system has a substantially greater capacity to participate in hemolymph pH regulation in fed than in unfed locusts.