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Author Evans, J.A.; Elliott, J.A.; Gorman, M.R.
Title Circadian effects of light no brighter than moonlight Type Journal Article
Year 2007 Publication Journal of Biological Rhythms Abbreviated Journal J Biol Rhythms
Volume 22 Issue 4 Pages 356-367
Keywords Animals; Biological Clocks/physiology/*radiation effects; *Circadian Rhythm; Cricetinae; Dose-Response Relationship, Radiation; Lighting/*methods; Male; Mesocricetus; Motor Activity; Oscillometry; Photic Stimulation/methods; *Photoperiod; Physical Conditioning, Animal; Time Factors
Abstract In mammals, light entrains endogenous circadian pacemakers by inducing daily phase shifts via a photoreceptor mechanism recently discovered in retinal ganglion cells. Light that is comparable in intensity to moonlight is generally ineffective at inducing phase shifts or suppressing melatonin secretion, which has prompted the view that circadian photic sensitivity has been titrated so that the central pacemaker is unaffected by natural nighttime illumination. However, the authors have shown in several different entrainment paradigms that completely dark nights are not functionally equivalent to dimly lit nights, even when nighttime illumination is below putative thresholds for the circadian visual system. The present studies extend these findings. Dim illumination is shown here to be neither a strong zeitgeber, consistent with published fluence response curves, nor a potentiator of other zeitgebers. Nevertheless, dim light markedly alters the behavior of the free-running circadian pacemaker. Syrian hamsters were released from entrained conditions into constant darkness or dim narrowband green illumination (~0.01 lx, 1.3 x 10(-9) W/cm(2), peak lambda = 560 nm). Relative to complete darkness, constant dim light lengthened the period by ~0.3 h and altered the waveform of circadian rhythmicity. Among animals transferred from long day lengths (14 L:10 D) into constant conditions, dim illumination increased the duration of the active phase (alpha) by ~3 h relative to complete darkness. Short day entrainment (8 L:16 D) produced initially long alpha that increased further under constant dim light but decreased under complete darkness. In contrast, dim light pulses 2 h or longer produced effects on circadian phase and melatonin secretion that were small in magnitude. Furthermore, the amplitude of phase resetting to bright light and nonphotic stimuli was similar against dimly lit and dark backgrounds, indicating that the former does not directly amplify circadian inputs. Dim illumination markedly alters circadian waveform through effects on alpha, suggesting that dim light influences the coupling between oscillators theorized to program the beginning and end of subjective night. Physiological mechanisms responsible for conveying dim light stimuli to the pacemaker and implications for chronotherapeutics warrant further study.
Address Department of Psychology, University of California, San Diego, La Jolla, CA 92093, usa. jaevans@ucsd.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 0748-7304 ISBN Medium
Area Expedition Conference
Notes PMID:17660452 Approved no
Call Number IDA @ john @ Serial 31
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Author Dacke, M.; Byrne, M.J.; Baird, E.; Scholtz, C.H.; Warrant, E.J.
Title How dim is dim? Precision of the celestial compass in moonlight and sunlight Type Journal Article
Year 2011 Publication Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences Abbreviated Journal Philos Trans R Soc Lond B Biol Sci
Volume 366 Issue 1565 Pages 697-702
Keywords Animals; Beetles/*physiology; Behavior, Animal; *Moon; *Sunlight; Video Recording
Abstract Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim--and the polarization pattern too weak--to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.
Address Department of Biology, University of Lund, Helgonavagen 3, 223 62 Lund, Sweden. marie.dacke@cob.lu.se
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 0962-8436 ISBN Medium
Area Expedition Conference
Notes PMID:21282173; PMCID:PMC3049003 Approved no
Call Number IDA @ john @ Serial 34
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Author Kyba, C.C.M.; Hölker, F.
Title Do artificially illuminated skies affect biodiversity in nocturnal landscapes? Type Journal Article
Year 2013 Publication Landscape Ecology Abbreviated Journal Landscape Ecol
Volume 28 Issue 9 Pages 1637-1640
Keywords skyglow; light pollution; biodiversity
Abstract The skyglow from cities at night is one of the most dramatic modifications that humans have made to Earth’s biosphere, and it is increasingly extending into nocturnal landscapes (nightscapes) far beyond urban areas. This scattered light is dim and homogenous compared to a lit street, but can be bright compared to natural celestial light sources, such as stars. Because of the large area of Earth affected by artificial skyglow, it is essential to verify whether skyglow is a selective pressure in nocturnal landscapes. We propose two scientific approaches that could examine whether skyglow affects biodiversity.
Address
Corporate Author Thesis
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 0921-2973 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number IDA @ john @ Serial 35
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Author Hölker, F.; Wolter, C.; Perkin, E.K.; Tockner, K.
Title Light pollution as a biodiversity threat Type Journal Article
Year 2010 Publication Trends in Ecology & Evolution Abbreviated Journal Trends Ecol Evol
Volume 25 Issue 12 Pages 681-682
Keywords *Biodiversity; Biological Clocks; Biological Evolution; Ecosystem; *Environmental Monitoring; *Environmental Pollutants; Light/*adverse effects
Abstract
Address
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Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 0169-5347 ISBN Medium
Area Expedition Conference
Notes PMID:21035893 Approved no
Call Number IDA @ john @ Serial 36
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Author Schoech, S.J.; Bowman, R.; Hahn, T.P.; Goymann, W.; Schwabl, I.; Bridge, E.S.
Title The effects of low levels of light at night upon the endocrine physiology of western scrub-jays (Aphelocoma californica) Type Journal Article
Year 2013 Publication Journal of Experimental Zoology. Part A, Ecological Genetics and Physiology Abbreviated Journal J Exp Zool A Ecol Genet Physiol
Volume 319 Issue 9 Pages 527-538
Keywords Animals; Corticosterone/blood; Ecosystem; Female; *Light; Male; Melatonin/blood; Passeriformes/*physiology; *Photoperiod; Reproduction/*physiology; Testosterone/blood
Abstract Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native habitat. Amongst the possible factors that influence this advance (e.g., food availability, microclimate, predator regime, etc.), is exposure to artificial lights at night (LAN). LAN could stimulate the reproductive axis of the suburban jays. Alternatively, LAN could inhibit pineal melatonin (MEL), thus removing its inhibitory influence on the reproductive axis. Because Florida scrub-jays are a threatened species, we used western scrub-jays (Aphelocoma californica) to investigate the effects of LAN upon reproductive hormones and melatonin. Jays were held under conditions in which the dark-phase of the light:dark cycle was without illumination and then under low levels of LAN. Under both conditions, birds were exposed first to short-days (9.5L:14.5D) that were gradually increased to long-days (14.5L:9.5D). At various times, blood samples were collected during the light part of the cycle to measure reproductive hormones (luteinizing hormone, LH; testosterone, T; and estradiol, E2 ). Similarly, samples to assess melatonin were collected during the dark. In males, LAN caused a depression in LH levels and levels were approximately 4x greater under long- than short-days. In females, there was no effect of LAN or photoperiod upon LH. LAN resulted in depressed T levels in females, although there was no effect on T in males. E2 levels in both sexes were lower under LAN than under an unlighted dark-phase. Paradoxically, MEL was higher in jays under LAN, and under long-days. MEL did not differ by sex. LAN disrupted the extraordinarily strong correlation between T and E2 that existed under unlighted nocturnal conditions. Overall, our findings fail to support the hypothesis that LAN stimulates the reproductive axis. Rather, the data demonstrate that LAN tends to inhibit reproductive hormone secretion, although not in a consistent fashion between the sexes.
Address Department of Biological Sciences, University of Memphis, Memphis, Tennessee
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Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 1932-5223 ISBN Medium
Area Expedition Conference
Notes PMID:23970442 Approved no
Call Number IDA @ john @ Serial 37
Permanent link to this record