Oxygen consumption and body temperature of active and resting honeybees

Abstract

We measured the energy turnover (oxygen consumption) of honeybees ( Apis mellifera carnica), which were free to move within Warburg vessels. Oxygen consumption of active bees varied widely depending on ambient temperature and level of activity, but did not differ between foragers (>18 d) and middle-aged hive bees (7–10 d). In highly active bees, which were in an endothermic state ready for flight, it decreased almost linearly, from a maximum of 131.4 μl O 2 min −1 at 15 °C ambient temperature to 81.1 μl min −1 at 25 °C, and reached a minimum of 29.9 μl min −1 at 40 °C. In bees with low activity, it decreased from 89.3 μl O 2 min −1 at 15 °C to 47.9 μl min −1 at 25 °C and 14.7 μl min −1 at 40 °C. Thermographic measurements of body temperature showed that with increasing activity, the bees invested more energy to regulate the thorax temperature at increasingly higher levels (38.8–41.2 °C in highly active bees) and were more accurate. Resting metabolism was determined in young bees of 1–7 h age, which are not yet capable of endothermic heat production with their flight muscles. Their energy turnover increased from 0.21 μl O 2 min −1 at 10 °C to 0.38 μl min −1 at 15 °C, 1.12 μl min −1 at 25 °C, and 3.03 μl min −1 at 40 °C. At 15, 25 and 40 °C, this was 343, 73 and 10 times below the values of the highly active bees, respectively. The Q 10 value of the resting bees, however, was not constant but varied in a U-shaped manner with ambient temperature. It decreased from 4.24 in the temperature range 11–21 °C to 1.35 in the range 21–31 °C, and increased again to 2.49 in the range 30–40 °C. We conclude that attempts to describe the temperature dependence of the resting metabolism of honeybees by Q 10 values can lead to considerable errors if the measurements are performed at only two temperatures. An acceptable approximation can be derived by calculation of an interpolated Q 10 according to the exponential function V O 2 =0.151×1.0784 T a (interpolated Q 10=2.12).