Oxygen consumption and body temperature rhythms in the golden spiny mouse: responses to changes in day length

The golden spiny mouse Acomys russatus is a rock dwelling rodent which lives in extremely arid and hot habitats. In Israel it is nocturnal except in areas in which it coexists with the common spiny mouse A. cahirinus. In such places it is diurnal. The daily rhythms of body temperature (Tb) and oxygen consumption (VO2) were compared in mice acclimated to two different photoperiod regimes in the laboratory: 8L:16D (short day) and 16L:8D (long day) at a constant ambient temperature. The daily rhythms of VO2 and of Tb in A. russatus were found to differ greatly under long and short photoperiod. Both parameters peaked at lights-out under both photoperiod regimes. In short day acclimated mice the effect of transmitter implantation was also studied. VO2 values at night were lower after implanting. The results of this study show that Tb and VO2 rhythms are altered by the lighting regimes. Seasonal acclimatization of thermoregulatory mechanisms in the golden spiny mouse are partly induced by changes in photoperiodicity.