The pineal and circadian rhythms of temperature selection and locomotion in lizards

Dipartimento di Scienze del Comportamento Animale e dell' Uomo, Pisa, Italy.
Physiology & Behavior (Impact Factor: 2.98). 06/1993; 53(5):911-5. DOI: 10.1016/0031-9384(93)90268-K
Source: PubMed


The existence of a circadian rhythm of behavioral temperature selection has been demonstrated in lizards (Podarcis sicula) held on a thermal gradient in constant darkness. This rhythm becomes temporarily abolished during 1 week following parietalectomy and 2-3 weeks following pinealectomy. Parietalectomy does not affect the locomotor rhythm, while pinealectomy invariably lengthens the freerunning period of this rhythm. These results support the contention of separate control systems for the temperature selection rhythm and the locomotor rhythm. As neither rhythm is definitively abolished by parietalectomy and pinealectomy, other pacemaking components exist elsewhere in the circadian system of Podarcis sicula which can control both rhythms.

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    • "Behavioral temperature regulation is present in many reptiles (Ellis et al. 2007, 2008; Cadena and Tattersall 2009). It follows a circadian rhythmicity that depends on photoperiod (Firth and Kennaway 1989; Jarling et al. 1989; Innocenti et al. 1993; Refinetti and Susalka 1997). Thus, in a long photoperiod (summer) a green lizard given a thermal choice will select a high body temperature (Tb), day and night. "
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    • "Several studies have demonstrated that the diel cycles of behavioural thermoregulation are true circadian rhythms, i.e. these cycles remain even under constant darkness (e.g. nocturnal lizard: Refinetti and Susalka 1997; diurnal lizards: Cowgell and Underwood 1979; Innocenti et al. 1993; Tosini and Menaker 1996; Ellis et al. 2006, 2008). Mechanisms underlying circadian rhythms such as melatonin production and the role of the pineal complex for thermoregulation have been reviewed elsewhere and will not be repeated here (see Underwood 1992; Tosini 1997; Lutterschmidt et al. 2003). "
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    Full-text · Article · Aug 2013 · Journal of Comparative Physiology B
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    • "However, the parietal eye seems to be involved in many physiological functions in lizards, such as thermoregulation and sun compass orientation. For instance, in the ruin lizard P. sicula ablation of parietal eye does not affect locomotor rhythmicity but temporarily abolishes the circadian rhythm of behavioral temperature selection (Innocenti et al., 1993). In I. iguana parietalectomy produces transient increase of body temperature during the first and second night following surgery (Tosini and Menaker, 1996). "
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    ABSTRACT: In mammals both the regulation of circadian rhythms and photoperiodic responses depend exclusively upon photic information provided by the lateral eyes; however, nonmammalian vertebrates can also rely on multiple extraocular photoreceptors to perform the same tasks. Extraocular photoreceptors include deep brain photoreceptors located in several distinct brain sites and the pineal complex, involving intracranial (pineal and parapineal) and extracranial (frontal organ and parietal eye) components. This review updates the research field of the most recent acquisitions concerning the roles of extraocular photoreceptors on circadian physiology and behavior, particularly photic entrainment and sun compass orientation.
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