Daily rhythms of body temperature in Acomys russatus: Their response to photoperiod manipulations and melatonin

1. The effects of photoperiod (16L:8D; 8L:16D) and melatonin treatment (50 μg for seven days) on daily rhythms of body temperature (T(b)) were studied in golden spiny mice Acomys russatus, kept at a constant ambient temperature of 28°C. 2. Results show different patterns of daily T(b) rhythms under the different photoperiod regimes. As a response to melatonin, mice under both photoperiods increased T(b) while rhythm percentage decreased. A phase shift of about 10 h in T(b) acrophase was noted in mice acclimated to 8L:16D. 3. Differences in the patterns of T(b) daily rhythms under the different photoperiod regimes, and difference in response to melatonin, may result from higher endogenous melatonin levels in long scotophase acclimated mice.