Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: I. Respiratory metabolism and energy consumption of unloaded and loaded workers during locomotion

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Abstract
The respiratory metabolism of workers of Messor capitatus (Latreille) was measured using standard micro‐Warburg techniques on single individuals. The experiments were carried out at 10, 20, 25, 30 and 40oC, and the respiratory quotient (RQ), measured for the same individuals at 30oC, was found to be 0.77. The specific respiratory rate (y, in μl O2/mg dry weight/h) could be described by the following equation: Iny = ‐2.24 + 0.098r ‐0.258 In W; where T is temperature and W is the dry weight in mg. The Q10 for M. capitatus in the temperature interval 20–30oC was 3.4, a higher value than for other ants.The energy costs of movement and carrying were determined by using the RQ to convert the continuous measurement of CO2 produced at 30oC by Enfiuran anaesthetized workers (‘resting metabolism’), by running workers and by workers loaded with a 20 mg weight to units of energy. The resting metabolism was 10.0±1.0 mJ/mg fresh weight/h. The cost of running (Y in joule per km) could be described by: Y = 3.865 + 0.363 Wf, where Wf is fresh weight in mg. The cost of transport for all experiments could be expressed as 0.64 × the cost of running.