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Braunstein S, Bennett NC, Voigt C, Oosthuizen MK. Differential locomotor activity responses to day-time light intensity in juvenile and adult solitary Cape mole-rats, Georychus capensis (Rodentia: Bathyergidae). Chronobiol Int 2023; 40:1084-1096. [PMID: 37667495 DOI: 10.1080/07420528.2023.2253298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 08/11/2023] [Accepted: 08/24/2023] [Indexed: 09/06/2023]
Abstract
The Cape mole-rat (Georychus capensis) is a solitary, strictly subterranean rodent that is responsive to light and entrains to photic cues despite having a reduced visual system. Circadian entrainment is maintained throughout life, but age can alter the amplitude of the response and re-entrainment time. Mole-rats are long-lived for their size which raises questions regarding the robustness of their circadian rhythms and how impacts their locomotor activity rhythms. The locomotor activity rhythms of juvenile and adult Cape mole-rats were investigated. They were exposed to pre-experimental and post-experimental control cycles under fluorescent lights, six 12 h light:12 h dark cycles of decreasing intensities and a constant dark cycle (DD). All animals exhibited more activity during the dark phases of all light regimes. Juveniles were more active than adults and displayed more variable activity during both the light and dark phases. Adults exhibited relatively stable levels of activity under all experimental conditions, whereas juvenile activity decreased as the light intensity was reduced. The amplitude of Cape mole-rat rhythms was consistently low, but similar across light regimes and between adults and juveniles. Cape mole-rats have functional circadian systems, are primarily nocturnal and respond differentially to light intensity depending on their age. Light intensity does not affect the locomotor activity responses of Cape mole-rats in a predictable manner, and could indicate more complex interactions with light wavelengths. The circadian systems of juveniles appear to be more sensitive than those of adults, although the mechanism of the light response remains unclear.
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Affiliation(s)
- S Braunstein
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - N C Bennett
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - C Voigt
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - M K Oosthuizen
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria, South Africa
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2
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Bano-Otalora B, Martial F, Harding C, Bechtold DA, Allen AE, Brown TM, Belle MDC, Lucas RJ. Bright daytime light enhances circadian amplitude in a diurnal mammal. Proc Natl Acad Sci U S A 2021; 118:e2100094118. [PMID: 34031246 PMCID: PMC8179182 DOI: 10.1073/pnas.2100094118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mammalian circadian rhythms are orchestrated by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN), which receives information about the 24 h light-dark cycle from the retina. The accepted function of this light signal is to reset circadian phase in order to ensure appropriate synchronization with the celestial day. Here, we ask whether light also impacts another key property of the circadian oscillation, its amplitude. To this end, we measured circadian rhythms in behavioral activity, body temperature, and SCN electrophysiological activity in the diurnal murid rodent Rhabdomys pumilio following stable entrainment to 12:12 light-dark cycles at four different daytime intensities (ranging from 18 to 1,900 lx melanopic equivalent daylight illuminance). R. pumilio showed strongly diurnal activity and body temperature rhythms in all conditions, but measures of rhythm robustness were positively correlated with daytime irradiance under both entrainment and subsequent free run. Whole-cell and extracellular recordings of electrophysiological activity in ex vivo SCN revealed substantial differences in electrophysiological activity between dim and bright light conditions. At lower daytime irradiance, daytime peaks in SCN spontaneous firing rate and membrane depolarization were substantially depressed, leading to an overall marked reduction in the amplitude of circadian rhythms in spontaneous activity. Our data reveal a previously unappreciated impact of daytime light intensity on SCN physiology and the amplitude of circadian rhythms and highlight the potential importance of daytime light exposure for circadian health.
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Affiliation(s)
- Beatriz Bano-Otalora
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Franck Martial
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Court Harding
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - David A Bechtold
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Annette E Allen
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Timothy M Brown
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Diabetes, Endocrinology and Gastroenterology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Mino D C Belle
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter EX4 4PS, United Kingdom
| | - Robert J Lucas
- Centre for Biological Timing, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
- Division of Neuroscience and Experimental Psychology, Faculty of Biology Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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Ackermann S, Bennett NC, Oosthuizen MK. The effect of varying laboratory conditions on the locomotor activity of the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and the diurnal Four-striped grass mouse (Rhabdomys dilectus). ZOOLOGY 2020; 141:125804. [DOI: 10.1016/j.zool.2020.125804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Revised: 05/05/2020] [Accepted: 05/08/2020] [Indexed: 01/19/2023]
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Locomotor activity in field captured crepuscular four-striped field mice, Rhabdomys dilectus and nocturnal Namaqua rock mice, Micaelamys namaquensis during a simulated heat wave. J Therm Biol 2020; 87:102479. [DOI: 10.1016/j.jtherbio.2019.102479] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/04/2019] [Accepted: 12/01/2019] [Indexed: 11/19/2022]
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van der Merwe I, Bennett NC, Haim A, Oosthuizen MK. Effects of the colour of photophase light on locomotor activity in a nocturnal and a diurnal South African rodent. Biol Lett 2019; 15:20190597. [PMID: 31573427 DOI: 10.1098/rsbl.2019.0597] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Many physiological and behavioural responses to varying qualities of light, particularly during the night (scotophase), have been well documented in rodents. We used varying wavelengths of day-time (photophase) lighting to assess daily responses in locomotor activity in the nocturnal Namaqua rock mouse (Micaelamys namaquensis) and diurnal four-striped field mouse (Rhabdomys pumilio). Animals were exposed to three light-dark cycle regimes: a short-wavelength- (SWLC, blue), a medium-wavelength- (MWLC, green) and a long-wavelength light-dark cycle (LWLC, red). Overall, daily locomotor activity of both species changed according to different wavelengths of light: the diurnal species displayed most activity under the SWLC and the nocturnal species exhibited the highest levels of activity under the LWLC. Both species showed an increase in diurnal activity and a decrease in nocturnal activity under the LWLC. These results indicate an attenuated responsiveness to long-wavelength light in the nocturnal species, but this does not appear to be true for the diurnal species. These results emphasize that the effect of light on the locomotor activity of animals depends on both the properties of the light and the temporal organization of activity of a species.
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Affiliation(s)
- Ingrid van der Merwe
- Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa.,Mammal Research Institute, University of Pretoria, Hatfield 0028, South Africa
| | - Abraham Haim
- Israeli Center for Interdisciplinary Studies in Chronobiology, University of Haifa, Haifa 31905, Israel
| | - Maria K Oosthuizen
- Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, South Africa.,Mammal Research Institute, University of Pretoria, Hatfield 0028, South Africa
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Miranda-Anaya M, Bosques-Tistler T, Ayala-García IN, Herrera-Argomaniz IJ, Pérez-Mendoza M, Carmona-Castro A. Affectations in photic and thermic circadian entrainment of the locomotor activity rhythm in obese volcano mouse Neotomodon alstoni. BIOL RHYTHM RES 2019. [DOI: 10.1080/09291016.2019.1607221] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Manuel Miranda-Anaya
- Facultad de Ciencias, Unidad Multidisciplinaria de Docencia e Investigación, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México
| | - Teresa Bosques-Tistler
- Facultad de Ciencias, Unidad Multidisciplinaria de Docencia e Investigación, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México
| | - Ivo N Ayala-García
- División de Tecnologías de Automatización e Información, Universidad Tecnológica de Querétaro, Querétaro, México
| | - Irvin J Herrera-Argomaniz
- División de Tecnologías de Automatización e Información, Universidad Tecnológica de Querétaro, Querétaro, México
| | - Moisés Pérez-Mendoza
- Facultad de Ciencias, Unidad Multidisciplinaria de Docencia e Investigación, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México
| | - Agustín Carmona-Castro
- Facultad de Ciencias, Unidad Multidisciplinaria de Docencia e Investigación, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México
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