Thermoregulation in bumblebees
Queens regulate thoracic temperature at 35–38 °C, and abdominal temperature at 31–36 °C while incubating their brood at ambient temperatures from 3 ° to 33 °C (Fig. 1).
The queen's brood clump, containing poikilothermic eggs, larvae and pupae, is incubated for long durations both during the day and at night (Figs. 2 and 3).
Brood temperature is maintained relatively independent from ambient temperature, but it does not appear to be maintained at specific temperature set-points. The difference between brood and ambient temperature during incubation is nearly 20 °C at an ambient temperature of 5 °C, and only 3 °C at 30 °C (Fig. 4).
The rate of oxygen consumption of incubating queens increases linearly with decreasing ambient temperatures (Fig. 6), and the temperature difference between the incubating queen and her brood is directly related to her rate of oxygen consumption (Fig. 7).
The “regulation” of brood temperature is explicable in terms of the regulation of abdominal temperature. The results are discussed with regard to vertebrate homeotherms, and with respect to energetics.
KeywordsOxygen Ambient Temperature Oxygen Consumption Temperature Difference Brood Temperature
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