Circadian locomotor activity rhythms of the diurnal Indian palm squirrel in constant light.
The parametric or tonic effects of light were studied in a recently established diurnal circadian model-the Indian palm squirrel, Funambulus pennanti. Sixteen squirrels (7 female, 9 male) were housed individually under varying constant light conditions (0.1 lux to 46 lux) with gross locomotor activity continuously monitored. Free-running period (tau), amplitude, mesor and day-to-day stability of the activity rhythm were determined using modified periodogram and iterative harmonic analyses, while the ratio of activity to rest time was estimated by eye-fit. The main findings were as follows: 1) tau did not vary between sexes or between light conditions, although a trend for tau to lengthen when light intensity was increased was noted; 2) amplitude and mesor did not show sex differences, but both sexes showed a decrease in amplitude and mesor when light intensity was decreased; 3) the stability of the activity rhythm was greater in males than in females, and a trend was observed for rhythm stability to decrease when light intensity was reduced. These descriptive data contribute to the growing literature on this diurnal species.
Department of Psychology, Monash University, Victoria, Australia. s.wilson-rajaratnam@surrey.ac.uk
S M
SM
Rajaratnam
J R
JR
Redman
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D007194:India; D008297:Male; D009043:Motor Activity / Q000502:physiology; D017440:Photoperiod; D012589:Sciuridae / Q000502:physiology*; D012727:Sex Characteristics