Modulation of cyclic CO2 release in response to endogenous changes of metabolism during pupal development of Zophobas rugipes (Coleoptera: Tenebrionidae)

Understanding the mechanisms of gas exchange regulation in insects currently is a hot topic of insect physiology. Endogenous variation of metabolism during pupal development offers a great opportunity to study the regulation of respiratory patterns in insects. Here we show that metabolic rates during pupal development of the tenebrionid beetle Zophobas rugipes reveal a typical U-shaped curve and that, with the exception of 9-day-old pupae, the time between two bursts of CO2 (interburst phase) was the only parameter of cyclic CO2 gas exchange patterns that was adjusted to changing metabolic rates. The volume of CO2 released in a burst was kept constant, suggesting a regulation for accumulation and release of a fixed amount of CO2 throughout pupal development. We detected a variety of discontinuous and cyclic gas exchange patterns, which were not correlated with any periods of pupal development, suggesting a high among individual variability. An occasional occurrence of continuous CO2 release patterns at low metabolic rates was very likely caused by single defective non-occluding spiracles.