Figure 1. Schematic diagram showing schedule of lighting conditions and sampling points. Arrow in series 2 indicates times at which animals were switched to constant darkness condition. Thin vertical bar joined by a horizontal bar indicates the beginning and end of the sampling period. Series 1 is the control condition, with animals maintained under light-dark conditions (alternating white bars [12 h light=300 lux,] and black bars [12 h dark]) throughout the experiment. Series 2 represents total darkness (alternating black dots on a white background [subjective day] and black bars).