Control of Resting Ventilation Rate in Grasshoppers Available to Purchase

We examined the effect of extracellular acid–base status and tracheal gas levels on the ventilation rate of resting Romalea guttata and Schistocerca americana grasshoppers. We manipulated haemolymph pH and [HCO₃^- ] within normal physiological ranges using injections of HCl, NaOH, NaHCO₃ and NaCl into the haemocoel. In contrast to terrestrial vertebrates, there was no evidence that extracellular acidification increases ventilation rate in grasshoppers. Elevation of haemolymph bicarbonate levels (by NaHCO₃ injection) increased ventilation rate, while depression of haemolymph bicarbonate levels (HCl injection) had no effect. Injection of NaHCO₃ also increased tracheal ⁠, suggesting that the effect of the NaHCO₃ injection might be mediated by a sensitivity of the ventilatory system to tracheal gases. We tested for effects of tracheal gases on ventilation rate by independently manipulating tracheal and using tracheal perfusions. Ventilation rate was positively correlated with tracheal and negatively correlated with tracheal ⁠. Increasing tracheal above normal resting levels or decreasing tracheal below normal levels decreased ventilation rate. We conclude that quiescent grasshoppers regulate tracheal and by varying ventilation rate and that both and in the trachea stimulate ventilation in normal, resting grasshoppers.