Gas exchange pattern in the two‐spot ladybird beetle, A dalia bipunctata , differs in dry vs. moist air

• Published in: Entomologia experimentalis et applicata 2016-08, Vol.160 (2), p.156-163
• Main Authors: Jõgar, Katrin, Kuusik, Aare, Metspalu, Luule, Ploomi, Angela, Williams, Ingrid H., Hiiesaar, Külli, Luik, Anne, Sibul, Ivar, Mänd, Marika
• Format: Article
• Language: English
• ISSN: 0013-8703; 1570-7458
• DOI: 10.1111/eea.12471

Gas exchange patterns in the ladybird beetle, A dalia bipunctata (L.) ( C oleoptera: C occinellidae), were investigated using an infrared gaseous analyser ( IRGA ) and a coulometric O 2 respirometer (manometric–volumetric system). Before testing, the beetles were kept either in dry (dehydrated) or moist (hydrated) conditions for 1 day. Their subsequent gas exchange patterns did not depend on their state of humidity but rather were controlled by the humidity of the insect chamber during gas exchange measurement. If this chamber contained dry air, the beetles exhibited CO 2 release by burst, which we interpreted as cyclic gas exchange ( CGE ) with inter‐burst periods, but if the chamber was switched to contain moist air, then cyclic CO 2 release was soon abandoned and a pattern of continuous gas exchange appeared. Measurements with the coulometric respirometer in moist air showed that continuous gas exchange was often associated with weak abdominal pulsations, which we interpreted as active ventilation. Their metabolic rate was lower during gas exchange cycles than during continuous gas exchange. We revealed that in the ladybird beetle metabolic rate increased in moist air when the gas exchange pattern transitioned from cyclic to continuous.