Meeting Abstract
Discontinuous gas exchange (DGE) is the best studied among gas exchange patterns in insects. DGE cycles comprise three phases, which are defined by spiracular state: close, flutter and open, although spiracle status has rarely been monitored directly. Instead, it is often assumed based on recorded respiratory gas traces. Furthermore, previous studies on the role of spiracle control in gas exchange patterns have focused almost exclusively on lepidopteran pupa during diapause. In this study we directly monitored muscular activity associated with DGE in adult locusts. We carried out electromyogram (EMG) recordings from the closer muscle of the second thoracic spiracle and from abdominal ventilation muscles simultaneously with recording of CO2 emission from a fully intact animal during DGE. We found that during the open phase, when CO2 emission rate is the highest, the spiracles open and close rapidly. The spiracle activity occurred in-phase with abdomen ventilation and in opposite phase to the last abdominal spiracle, thus facilitating a unidirectional flow of air through the grasshopper. Moreover, the spiracle instantaneous frequency (the frequency of spiracle transition from open to close state and vice versa) was correlated with the CO2 emission rate. We also found a strong correlation between the number of spiracle openings and the amount of CO2 that accumulates during the DGE cycle interburst (the close and flutter phases). We show that during the flutter phase abdominal ventilation is coupled with thoracic spiracle closure, suggesting gas exchange through the abdominal spiracles only.
