Altitudinal Variation In Phase Response Curves For The Himalayan Strains Of Drosophila Helvetica

We investigated the effects of natural light at night (LAN) in the field and artificial LAN in the laboratory on the circadian rhythm of pupal eclosion in a tropical wild type strain of Drosophila jambulina captured at Galle, Sri Lanka (6.1(o)N, 80.2(o)E). The influence of natural LAN, varying in intensity from 0.004 lux (starlight intensity) to 0.45 lux (moonlight intensity), on the entrainment pattern of the circadian rhythm of eclosion at 25(o) +/- 0.5(o)C was examined by subjecting the mixed-aged pupae to natural cycles of light and darkness at the breeding site of this strain in the field. The eclosion peak was approximately 2 h prior to sunrise, and the 24 h rhythmicity was the most robust. Effects of artificial LAN at 25(o) +/- 0.5(o)C were determined in the laboratory by subjecting pupae to LD 12:12 cycles in which the light intensity of the photophase was 500 lux in all LD cycles, while that of the scotophase was either 0 lux (complete darkness, DD), 0.5, 5, or 50 lux. In the 0 lux LAN condition (i.e., the control experiment), the eclosion peak was approximately 2 h after lights-on, and the 24 h eclosion rhythm was not as strong as in the 0.5 lux LAN condition. The entrainment pattern in 0.5 lux LAN was strikingly similar to that in the field, as the 0.5 lux LAN condition is comparable to the full moonlight intensity in the tropics. LAN at 0.5 lux dramatically altered both parameters of entrainment, as the eclosion peak was advanced by approximately 4 h and the 24 h eclosion rhythm was better than that of the control experiment. LAN at 5 lux, however, resulted in a weak eclosion rhythm that peaked in the subjective forenoon. Interestingly, the 50 lux LAN condition rendered the eclosion events unambiguously arrhythmic. After-effects of LAN on the period (tau) of the free-running rhythm and the nature of eclosion rhythm were also determined in DD by a single LD 12:12 to DD transfer. After-effects of the LAN intensity were observed on both the tau and nature of the eclosion rhythm in all four experiments. Pupae raised in 0.5 lux LAN exhibited the shortest tau (20.6 +/- 0.2 h, N = 11 for this and subsequent values) and the most robust rhythm, while pupae raised in 50 lux LAN had the longest tau (29.5 +/- 0.2 h) and weakest rhythm in DD. Thus, these results demonstrate the intensity of LAN, varying from 0 to 50 lux, profoundly influences the parameters of entrainment as well as free-running rhythmicity of D. jambulina. Moreover, the observed arrhythmicity in LD 12:12 cycles caused by the 50 lux LAN condition appeared to be the masking effect of relatively bright light at night, as the LD 12:12 to DD transfer restored the rhythmicity, although it was rather weak.

Section: Discussionsupporting

confidence: 82%

LIGHT AT NIGHT ALTERS THE PARAMETERS OF THE ECLOSION RHYTHM IN A TROPICAL FRUIT FLY,DROSOPHILA JAMBULINA

Thakurdas

Sharma

Vanlalhriatpuia

et al. 2009

“…This report is part of the ongoing investigations in our laboratory on the fundamental properties of the natural clock phenotypes of the tropical and subtropical species of Drosophila captured from Malaysia, Sri Lanka, Indonesia, India, etc. (Joshi et al, 1999;Keny et al, 2007aKeny et al, , 2007bKhare et al, 2002Khare et al, , 2004Khare et al, , 2005Satralkar et al, 2007). Recently, we demonstrated that dim nighttime irradiance in the range of 0 to 50 lux affected the pacemaker of D. jambulina that controls the pupal eclosion rhythm expressed in the larval stage (Thakurdas et al, 2009).…”

Section: Introductionmentioning

confidence: 98%

Nocturnal Illumination Dimmer Than Starlight Altered the Circadian Rhythm of Adult Locomotor Activity of a Fruit Fly

Thakurdas

Sharma

Sinam

et al. 2010

The effects of nocturnal irradiance tenfold dimmer than starlight intensity on the locomotor activity rhythm of Drosophila jambulina were investigated in two types of light-dark (12 h:12 h) cycles, in which light intensity of the photophase was 10 lux while that of the scotophase was either 0 lux for control flies or 0.0006 lux for experimental flies. Activity onset in the experimental flies was approximately 5.4 h prior to lights-on, so it occurred around midnight. However, activity onset of the control flies coincided almost with the lights-on. Nevertheless, activity offset was the same in both groups, occurring at lights-off. Duration of the active phase (alpha) and activity passes/fly/cycle (APC) in the experimental flies was far greater than in controls. After-effects of the nocturnal illumination of the light-dark cycles when the flies were transferred to constant darkness were evident as the period of the free-running rhythm was shortened, alpha was lengthened, and APC was enhanced in the experimental compared to control flies. Thus, very low photic sensitivity of these flies appears to be a physiological adaptation to dim-light ambiance in its natural breeding site in the field.

“…However, the cosinor procedure is little known outside the field of applied chronobiology; thus, it must be clearly explained in the Methods section for those readers of Chronobiology International who are less specialized and less familiar with this analytical procedure. Moreover, actual time series of measurements are often rather complex due to the superimposition of rhythms of different frequencies, biological noise, and environmental "masking" effects (Eriksen et al, 2006;Gorman et al, 2006;Keny et al, 2007aKeny et al, , 2007b. Thus, different and/or complementary statistical procedures are often required to detect rhythms and test specific hypotheses.…”

Section: Ethical Standards For Biological Rhythm Researchmentioning

confidence: 99%

“…Particulars about the age, sex, strain, and breeding history/genetic manipulation of study organisms, such as neurospora, drosophila, fish, birds, and laboratory animals also must be conveyed (e.g., Azzaydi et al, 2007;Hanifin et al, 2006;Keny et al, 2007aKeny et al, , 2007bLopez-Olmeda et al, 2006;Merrow et al, 2006;Weinert & Schottner, 2007). Inbred strains of various species have been developed for specific research.…”

Section: Chronobiological Criteriamentioning

confidence: 99%

Ethical and Methodological Standards for Laboratory and Medical Biological Rhythm Research

Portaluppi

Touitou

Smolensky

2008

316

148

The main objectives of this article are to update the ethical standards for the conduct of human and animal biological rhythm research and recommend essential elements for quality chronobiological research information, which should be especially useful for new investigators of the rhythms of life. A secondary objective is to provide for those with an interest in the results of chronobiology investigations, but who might be unfamiliar with the field, an introduction to the basic methods and standards of biological rhythm research and time series data analysis. The journal and its editors endorse compliance of all investigators to the principles of the Declaration of Helsinki of the World Medical Association, which relate to the conduct of ethical research on human beings, and the Guide for the Care and Use of Laboratory Animals of the Institute for Laboratory Animal Research of the National Research Council, which relate to the conduct of ethical research on laboratory and other animals. The editors and the readers of the journal expect the authors of submitted manuscripts to have adhered to the ethical standards dictated by local, national, and international laws and regulations in the conduct of investigations and to be unbiased and accurate in reporting never-before-published research findings. Authors of scientific papers are required to disclose all potential conflicts of interest, particularly when the research is funded in part or in full by the medical and pharmaceutical industry, when the authors are stock-holders of the company that manufactures or markets the products under study, or when the authors are a recent or current paid consultant to the involved company. It is the responsibility of the authors of submitted manuscripts to clearly present sufficient detail about the synchronizer schedule of the studied subjects (i.e., the sleep-wake schedule, ambient light-dark cycle, intensity and spectrum of ambient light exposure, seasons when the research was conducted, shift schedule in studies involving shift work, and menstrual cycle stage in studies involving young women). Rhythm analysis of time series data should be performed with the perspective that rhythms of different periods might be superimposed upon the observed temporal pattern of interest. A variety of different and complementary statistical procedures can be used for rhythm detection. Fitting a mathematical model to the time series data provides a better and more objective analysis of time series data than simple data inspection and narrative description, and if rhythmicity is documented by objective methods, its characterization is required by relevant parameters such as the rhythm's period (tau), MESOR (time series average), amplitude (range of temporal variation), acrophase (time of peak value), and bathyphase (time of trough value). However, the assumptions underlying the time series modeling must be satisfied and applicable in each case, especially the assumption of sinusoidality in the case of cosinor analysis, before it can be accepted...