Active regulation of respiration and circulation in pupae of the codling moth ( Cydia pomonella)

Abstract

Regulation of autonomic physiological functions has been investigated by means of multisensor electronic methods, including electrocardiographic recording of heartbeat, strain-gauge recording of extracardiac hemocoelic pulsations (EHPs), anemometric recording of air passage through spiracles and respirographic recording of O 2 consumption and CO 2 output. Pupae of Cydia exhibit continuous respiration without remarkable bursts of CO 2. The dorsal vessel of these pupae exhibited regular heartbeat reversals characterized by shorter intervals of faster (forward oriented or anterograde) pulsations and longer intervals of slower (backward oriented or retrograde) peristaltic waves. The periodically repeated EHPs were present during the whole pupal interecdysial period. The internal physiological mechanisms regulating the cardiac (heartbeat) and extracardiac (EHP) pulsations were completely independent for most of the pupal instar. Simultaneous multisensor analysis revealed that the anterograde heartbeat of the dorsal vessel had similar but not identical frequency with EHPs. During advanced pharate adult development, frequency of cardiac and extracardiac pulsation periods profoundly increased until almost uninterrupted pulsation activity towards adult eclosion. At this time, the cardiac and extracardiac pulsations occasionally performed in concert, which enhanced considerably the efficacy of hemolymph circulation in pharate adults with high metabolic rates. The fastest hemolymph flow through the main body cavity was always associated with EHPs and with anterograde heartbeat. Simple physical diffusion of O 2 and CO 2 through spiracles (diffusion theory of insect respiration) does not play a significant role in pupal respiration. Instead, several kinds of regulated, mechanical ventilations of the tracheal system, including EHPs are responsible for effective tracheal ventilation.