Coulometric Measurement of Oxygen Consumption in Insects

Abstract

The energy metabolism of an animal may be affected by environmental factors (temperature, light, partial pressure of oxygen, etc.) as well as organismic properties (reproductive and nutritional status, stage of development, etc.). Changes in energy metabolism due to specific metabolic factors can only be interpreted in a meaningful way when all other organismic and environmental factors have been standardized or controlled during an experiment. In practice, this is best achieved when the energy metabolism of an animal is measured over long periods of time under environmental conditions that approximate those of the normal habitat. Of particular importance in the interpretation of metabolic data is the establishment of normal daily changes in energy metabolism due to circadian rhythms in locomotor activity. In general, animals display their daily periodicity only in an environment that does not stress them. For example, a single honeybee survives well for more than 1 week when the conditions inside the respiratory chamber approximate those in the beehive (the presence of beeswax and honey), but would die within a few hours when deprived of those conditions (Heusner and Stussi 1964). Drosophila display striking circadian variations in energy metabolism when placed in a simple glass respiratory chamber that contains a glucose-agar medium (Heusner 1970).