Figure 6. Effects of decreasing photoperiods on robustness, mesor, and amplitude of circadian rhythms.

Mean ± SEM (A) robustness, (B) mesor, and (C) amplitude of the circadian waveforms of male Siberian hamsters raised in 15 L and transferred to one of seven experimental photoperiods ranging from 9 L to 15 L (indicated along the abscissae). *P≤0.05 and **P≤0.005 vs. 15 L value.