The oxygen consumption rate during embryogenesis of Acartia tonsa subitaneous eggs were measured at different temperatures (10, 15, 17, 21, 24 and 28 degrees C) with nanorespirometry. The oxygen consumption was constant during the embryogenesis but increased rapidly at hatching time. The mean +/- SD oxygen consumption rate increased exponentially with temperature and ranged from 0.09 +/- 0.04 (10 degrees C) to 0.54 +/- 0.09 nmol O(2) egg(-1) h(-1) (28 degrees C). The mean +/- SD Q(10)-value was 2.51 +/- 0.15. Calculations of energy consumption during embryogenesis ranged from 1.86 to 18.28 mJ depending on temperature and development time. We conclude that the effect of temperature on oxygen consumption rate was far less important than the prolonged development time when calculating the energy consumed during embryogenesis.