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Author Gorman, M. R.; Elliott, J. A.
Title Dim nocturnal illumination alters coupling of circadian pacemakers in Siberian hamsters, Phodopus sungorus Type Journal Article
Year 2004 Publication Journal of Comparative Physiology A Abbreviated Journal Comp Physiol A
Volume 190 Issue 8 Pages 631-
Keywords animals; rodents; seasonal timing
Abstract The circadian pacemaker of mammals comprises multiple oscillators that may adopt different phase relationships to determine properties of the coupled system. The effect of nocturnal illumination comparable to dim moonlight was assessed in male Siberian hamsters exposed to two re-entrainment paradigms believed to require changes in the phase relationship of underlying component oscillators. In experiment 1, hamsters were exposed to a 24-h light-dark-light-dark cycle previously shown to split circadian rhythms into two components such that activity is divided between the two daily dark periods. Hamsters exposed to dim illumination (<0.020 lx) during each scotophase were more likely to exhibit split rhythms compared to hamsters exposed to completely dark scotophases. In experiment 2, hamsters were transferred to winter photoperiods (10 h light, 14 h dark) from two different longer daylengths (14 h or 18 h light daily) in the presence or absence of dim nighttime lighting. Dim nocturnal illumination markedly accelerated adoption of the winter phenotype as reflected in the expansion of activity duration, gonadal regression and weight loss. The two experiments demonstrate substantial efficacy of light intensities generally viewed as below the threshold of circadian systems. Light may act on oscillator coupling through rod-dependent mechanisms.
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Call Number (down) LoNNe @ schroer @ Serial 1590
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Author Ikeda, Masayuki; Sagara, Masami; Inoué, Shojiro
Title Continuous exposure to dim illumination uncouples temporal patterns of sleep, body temperature, locomotion and drinking behavior in the rat Type Journal Article
Year 2000 Publication Neuroscience Letters Abbreviated Journal
Volume 279 Issue 3 Pages 185-189
Keywords animals; rodents; animal behaviour
Abstract Dissociable circadian rhythms of sleep and body temperature in primates are thought to be regulated by independent oscillators whereas the uncoupling of circadian rhythms has not been well described in other mammals. Therefore, we made simultaneous recordings of non-rapid-eye-movement-sleep (NREMS), rapid-eye-movement-sleep (REMS), brain temperature, intraperitoneal temperature, locomotion and drinking activity under light-dark (LD) and continuous dim illumination (dim LL) and analyzed their interrelations. The rhythmic patterns of body temperature, locomotion and drinking were modified on the 12th circadian day of dim LL, while the mean body temperature as well as mean occurrence of drinking and locomotor activities did not change significantly. In contrast, dim LL exposure significantly increased the total time spent in NREMS during the resting phase of dim LL and increased REMS episodes during the active phase of dim LL. The diverse effects of dim LL exposure on the recorded phenomena suggest that temporal patterns of sleep were the most sensitive to perturbations of lighting and that differential oscillatory mechanisms may regulate sleep and other circadian rhythms in the rat.
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Call Number (down) LoNNe @ schroer @ Serial 1591
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Author Imsland, A.K.; Roth, B.; Foss, A.; Vikingstad, E.; Stefansson, S.O.; Pedersen, S.; Sandvik, T.; Norberg, B.
Title Long-term effect of photoperiod manipulation on growth, maturation and flesh quality in Atlantic halibut. Type Journal Article
Year 2009 Publication Aquaculture Research Abbreviated Journal
Volume 40 Issue 11 Pages 1260-1269
Keywords animals; fish; aquaculture; animal production
Abstract The aim of this study was to investigate the effect of continuous light at different stages during the production cycle of Atlantic halibut Hippoglossus hippoglossus L. on growth, age at first maturity, endocrine parameters and flesh quality. A group of juvenile halibut [mean (SD), initial weight 191.3 g (44.7)] was reared in indoor tanks under ambient temperature conditions for 38 months until harvesting (mean final weight, 4.6 kg). The entire photoperiod experiment was divided into four phases, where the fish in each phase were exposed to either natural photoperiod (62°33&#8242;N) or continuous light (L). Thus, the following five photoperiod combinations were tested: (a) Control group (NNNN), (b) Group 2A (NLNN), (c) Group 2B (NNLN), (d) Group 2C (NNNL) and (e) Production group (LNNN). Exposure to continuous light stimulated growth, and the final mean weights of Groups 2A and 2B were 23% and 11% higher than those of the Control group (NNNN). The final plasma 11-ketotestosteron levels were lower in Groups 2A (2.94 ng mL&#8722;1) and 2B (2.46 ng mL&#8722;1) compared with the Control (5.29 ng mL&#8722;1), Group 2C (5.09 ng mL&#8722;1) and the Production group (4.78 ng mL&#8722;1) during spring 2007 (age 4 years), indicating higher age at first maturity in Groups 2A and 2B. Photoperiod regime had only a minor, and transient, effect on flesh-quality traits of the fish, whereas a significant seasonal effect was seen with a tendency towards increased gaping, lower pH, lower hardness and lower shear force in July compared with December and March.
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Call Number (down) LoNNe @ schroer @ Serial 1592
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Author Jung, K.; Kalko, E.K.
Title Where forest meets urbanization: foraging plasticity of aerial insectivorous bats in an anthropogenically altered environment Type Journal Article
Year 2010 Publication Journal of Mammalogy Abbreviated Journal J. Mammal.
Volume 91 Issue 1 Pages 144-153
Keywords animals; flying mammals; acoustic monitoring; anthropogenic influence; artificial light; bat activity; Chiroptera; habitat plasticity; moon
Abstract Given worldwide rapid human population growth resulting in degradation or loss of habitats, it is important to understand how anthropogenic factors affect species presence and activity, and consequently, how well species tolerate or adapt to anthropogenically altered environments. This study, conducted in Panama, focuses on aerial insectivorous bats, a highly mobile and ecologically important, but largely understudied group. Acoustic monitoring was used to investigate habitat use in a tropical forest-town interface and microhabitat use around streetlights differing in wavelength (type of light) and accessibility (distance to vegetation). Plasticity in microhabitat use also was examined in relation to season and moonlight. We recorded a total of 25 aerial insectivorous bat species in the study area and found a subset of 20 species in town of which 18 frequently foraged around streetlights. Bat activity (passes/min) was lowest at the forest site, highest at streetlights, and intermediate in the dark areas of town. General bat activity at streetlights was concentrated at bluish-white lights compared to yellow-white and orange lights. However, bats revealed species-specific microhabitats with regard to light type, distance to vegetation, and relative light intensity. Season and moon phase affected microhabitat use around streetlights leading to microhabitat plasticity of individual species. Thus, in the forest-town interface most, but not all, aerial insectivorous bats were present in town and regularly foraged around streetlights, suggesting a species-specific tolerance for habitat alteration. Bats foraging at streetlights used microhabitats, and some species even changed microhabitats, according to season or moon phase. This indicates species-specific requirements for microhabitats and the importance of preserving habitat heterogeneity.
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Call Number (down) LoNNe @ schroer @ Serial 1593
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Author Liu, Y; Li, X.; Xu, G. F.; Bai, S. Y.; Zhang, Y. Q.; Gu, W.; Mou, Z. B.
Title Effect of photoperiod manipulation on the growth performance of juvenile lenok, Brachymystax lenok (Pallas, 1773) Type Journal Article
Year 2015 Publication Journal of Applied Ichtyology Abbreviated Journal
Volume 31 Issue 1 Pages 120-1124
Keywords animals; fish; photoperiod; growth
Abstract The effect of four different light regimes on growth was studied in lenok, Brachymystax lenok. Fish with average weights of 5.5 g were subjected to four different photoperiods (0L:24D, 6L:18D, 12L:12D and 24L:0D) for 35 days. The specific growth rate (SGR) of lenok in 24-h darkness had a significantly higher SGR than those in the continuous light regime (P < 0.05); however, there was no significant difference among fish exposed to 6L:18D, 12L:12D and 24L:0D photoperiods. There was a tendency for higher food intake over the light period extension from 0L to 24L, and feed intake was significantly higher in the continuous light group than in 24-h darkness (P < 0.05). No significant difference in feed conversion efficiency (FCE) was observed between fish exposed to 0L:24D and 6L:18D photoperiods, however, the FCE in both photoperiods was significantly higher than that in the other two groups. The final survival rate of juveniles varied from 79.67 to 95.33%, with significant differences among experimental groups. Fish tested in continuous illumination spent much more energy on respiration and excretion while depositing less energy for growth than in the other photoperiods. In contrast, fish in 24-h darkness deposited more energy for growth and spent less energy on respiration and excretion. Results show that photoperiod manipulation can affect growth, and that a continuous dark regime could improve growth in lenok at this stage of development.
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Call Number (down) LoNNe @ schroer @ Serial 1595
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