Circadian locomotor activity in the juvenile red eared turtle Trachemys scripta elegans: free running and entrainment

Abstract

Long-term circadian locomotor activity under different light conditions and its corresponding free running periods were studied in the juvenile red-eared turtle Trachemys scripta elegans. Diurnal activity and a long free running period in darkness was observed in LD 12:12, skeleton photoperiod, and long and short days (LD 16:08, LD 08:16, respectively). Anticipation of activity to lights-on and length of activity phase depends on the photoperiod used. After-effects were observed in free running conditions after long day photoperiods. Constant light effect produces mainly the lack of circadian rhythm after a few days of period lengthening and the lack of rhythm may persist for a few days after re-entering constant darkness conditions. The results of the present report indicate that in T. scripta elegans, it is suitable to perform studies on circadian biology in juvenile turtles and its interaction with changes of photoperiod at constant temperature.