Factors affecting oxygen consumption in the woodlouse Porcellio scaber latr.

1. There is a well-defined time sequence in the oxygen consumption of Porcellio scaber. A maximal rate (the 'active rate') is obtained in woodlice subjected to the maximal disturbance of food presentation, handling and light. After initial exploratory activity has ceased, the oxygen consumption declines through a series of 'excited rates' towards the 'standard rate' which is approached after 2-3 hr equilibration in a respirometer. 2. The rate following starvation for 1-3 days is similar to the standard rate. 3. Thermal acclimation has no significant effect on the slope or the level of the rate: temperature curves for the excited or the standard rate of oxygen consumption of Porcellio scaber. 4. The rate: temperature curves for active, excited and standard oxygen consumption of Porcellio scaber have a double sigmoid form with high temperature coefficients at the extremes of the experimental temperature range. 5. The respiration rate of a homogenate of Porcellio scaber in the presence of 9.0 mM succinate is intermediate between the active and standard rate of the intact animal. 6. The maximum scope for activity is highest at 10-15°C and falls towards both higher and lower experimental temperatures. 7. The overall oxygen consumption of intact Porcellio scaber may reflect the summation of 'cellular' and 'organismic' metabolic components which account for approximately equal proportions of the total metabolism at the normal environmental temperature range of 10-15°C. Below this temperature the cellular component is predominant whilst at the upper limits of the experimental temperature range oxidative metabolism is represented solely by the organismic component.