Circadian locomotor rhythms in the desert iguana I. The role of the eyes and the pineal |
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Authors: | Daniel S Janik Michael Menaker |
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Institution: | (1) Department of Biology, University of Oregon, 97403 Eugene, OR, USA;(2) Present address: Department of Psychology, University of Illinois, 603 E Daniel St., 61820 Champaign, IL, USA;(3) Present address: Department of Biology, Gilmer Hall, University of Virginia, 22901 Charlottesville, VA, USA |
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Abstract: | Summary The pineal and the eyes are known to be important components in the circadian system of some species of lizards; their effects may be mediated by the hormone melatonin. We examined the role played by these structures in the desert iguana (Dipsosaurus dorsalis). Surgical removal of the pineal had no effect on circadian locomotor rhythms, even though this procedure abolished the circadian rhythm of melatonin in the blood. Furthermore, when the isolated pineal of Dipsosaurus was studied in organ culture, it showed no circadian rhythm of melatonin secretion, as do pineals of some other lizard species, although it did produce large quantities of this hormone. Bilateral ocular enucleation had only small effects on the freerunning period of locomotor rhythms, without affecting melatonin levels in the blood. Behavioral circadian rhythms persisted in desert iguanas subjected to both enucleation and pinealectomy. These data suggest that neither the pineal nor the eyes are central components of the circadian pacemaking system in Dipsosaurus, nor is melatonin critically involved in maintaining its organization.Abbreviations
CT
circadian time
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ZT
zeitgeber time
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LL
constant light
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LD
light-dark cycle
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DD
constant darkness
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freerunning circadian period |
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Keywords: | Circadian Lizard Pineal Eye Melatonin |
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