Circadian rhythms of locomotor activity and temperature selection in sleepy lizards, <Emphasis Type="Italic">Tiliqua rugosa</Emphasis> |
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Authors: | David J Ellis Bruce T Firth Ingrid Belan |
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Institution: | (1) Discipline of Anatomical Sciences, School of Medical Sciences, The University of Adelaide, Adelaide, SA, 5005, Australia;(2) School of Nursing and Midwifery, Flinders University, Adelaide, SA, 5001, Australia |
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Abstract: | This study examined whether the daily rhythms of locomotor activity and behavioural thermoregulation that have previously
been observed in Australian sleepy lizards (Tiliqua rugosa) under field conditions are true circadian rhythms that persist in constant darkness (DD) and whether these rhythms show
similar characteristics. Lizards held on laboratory thermal gradients in the Australian spring under the prevailing 12-hour
light : dark (LD) cycle for 14 days displayed robust daily rhythms of behavioural thermoregulation and locomotor activity.
In the 13-day period of DD that followed LD, most lizards exhibited free-running circadian rhythms of locomotor activity and
behavioural thermoregulation. The predominant activity pattern displayed in LD was unimodal and this was retained in DD. While
mean levels of skin temperature and locomotor activity were found to decrease from LD to DD, activity duration remained unchanged.
The present results demonstrate for the first time that this species’ daily rhythm of locomotor activity is an endogenous
circadian rhythm. Our results also demonstrate a close correlation between the circadian activity and thermoregulatory rhythms
in this species indicating that the two rhythms are controlled by the same master oscillator(s). Future examination of seasonal
aspects of these rhythms, may, however, cause this hypothesis to be modified. |
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Keywords: | Tiliqua rugosa Reptiles Thermoregulation Activity Circadian |
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