The influence of temperature on respiration of diapausing pupae of Pieris brassicae (Lepidoptera)

Abstract

The respiration of diapausing Pieris pupae has been measured at different temperatures between 5 and 35°C in animals maintained at 20°C, either 14 or 74 days after larvo-pupal ecdysis or at 5°C for 30 or 60 days. The sudden transfer of animals from 5 to 15, 20, 25, 30, 35°C or from 20 to 30, 35°C results in a respiratory overshoot whose characteristics (duration, height, extra-respiration) depend on experimental conditions. After a certain period of acclimation, overshoots are eliminated. The respiratory rate except for animals maintained during 74 days at 20°C can then be represented as an exponential function of temperature. The Q 10 values change according to the treatment given to pupae. The respiratory rate of male pupae is higher than that of female ones. The following points are discussed: 1. 1.|The meaning of overshoots is analysed according to economy and metabolic homeostasis, showing the existence of acclimation. 2. 2.|Exponential curves which are not relevant to non-diapausing pupae or to the diapausing ones taken at larvo-pupal molting are characteristic of steady metabolism. These curves can be interpreted as the result of the temperature effect on a master respiratory reaction which would then be rate limiting. 3. 3.|Wintering leads to gradual and slow adaptation to cold temperatures which brings both a respiratory increase, a decrease of the Q 10 and of the activation energy of the master reaction.