The effect of fasting on activity and resting metabolism in the sand cricket, Gryllus firmus: a multivariate approach.

Heat increment of feeding (HIF) is a ubiquitous feature of animals, and corresponds to a conspicuous rise in metabolism after a meal, induced by the release of energy due to digestion and absorption of foodstuffs. However, there exists great variation both in the duration and magnitude of HIF. In insects, HIF is well known, and it appears to be dramatic, especially in immature stages. However, little is known about the effect of HIF on different aspects of metabolism. We determined metabolic rate as CO2 production in fasted and non-fasted nymphs of the sand cricket (Gryllus firmus). A number of metabolic variables were computed from the simultaneous activity record: activity, resting, minimum, maximum and average metabolic rate. Our results suggest that there is a general effect of fasting in metabolic rate but with a graded response: the larger the influence of activity on the metabolic variable, the less is the effect of fasting that was detected.