Static and dynamic approaches yield similar estimates of the thermal sensitivity of insect metabolism

Abstract

Thermal sensitivity of metabolism (estimated by the temperature coefficient, Q10) is important for understanding ectotherm responses to temperature, but can only be measured empirically. Several strategies can be used to estimate thermal sensitivity. Static temperature respirometry uses measurements of metabolic rate taken at a series of temperatures, either by using different individuals at each temperature (independent STR, iSTR), or the same individual at several different temperatures (repeated STR, rSTR). Q10 can also be estimated from measurements of metabolic rate during a monotonic change in temperature (dynamic temperature respirometry, DTR), using either upwards (uDTR) or downwards (dDTR) temperature ramps. We compared estimates of Q10 of metabolic rate in adult females of the fall field cricket, Gryllus pennsylvanicus, derived from measurements made between 8 and 35°C, using iSTR, rSTR, dDTR and uDTR. We also controlled for aging effects during rSTR, and for ramp rate during DTR. We found that all measurement methods yielded statistically comparable measures of Q10. However, DTR provided higher absolute estimates of metabolic rate than STR. Thus, it appears that the different methods provide comparable estimates of Q10, allowing meta-analyses to utilize estimates of Q10 derived from different methods, and for the measurement strategy to be tailored to the characteristics of the organism.