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Seenappa, S. N. (2012). Effect of Photoperiodism on Feeding and Defecation in Compost Earthworm Eudrilus eugeniae. Universal Journal of Environmental Research and Technology, 2(1), 21–25.
Abstract: The effects of different fixed photoperiodic regimes on the rate of feeding and defecation in the epigeic
oligochaete (Eudrilus eugeniae) has been investigated. The different photoperiods stipulated were Natural 12hr Light: 12hr Dark (natural LD 12:12), Reversal of 12hr Light: 12hr Dark ( reversal LD 12:12), 24hr Light source (L 24), 24hr Dark (D 24) and control set (natural rhythm) were experienced by E. eugeniae in the course of the study. The experiments were carried out during the ambient winter (26 degree C + 2 ) and all clitellate worms showed varied feeding and defecation activities. Worms fed actively only during night times under natural LD 12: 12. when exposed to reversal LD 12:12 revealed acclimatization to the changed conditions of day and night by the end of 2nd week and started feeding voraciously. Worms that were maintained in D 24 showed enhanced feeding rate with increased biomass over the worms that were maintained in natural LD 12:12 and natural rhythm (control set). ANOVA and ANCOVA tests applied revealed that the total darkness or diffused light without any disturbance influenced the feeding rate of worms that in turn showed higher production of defecation as vermicompost. The critical difference (C.D.) of ANOVA was 0.98(0.05%) and the difference for testing among treatments in ANCOVA was 781191.15(0.05). Resynchronization pattern were seen when changed to reversal LD 12:12 from natural LD 12:12. Observations revealed that worms were confused from day 1-4 when any changed photoperiodic devices were fixed other than their regular normal pattern of Light and Dark cycle and later got acclimatization into the induced photoperiodic cycles. The study apart from proving the exogenous factors on the photoperiodic effects also proven the importance of darkness to the worms in defecation that has importance in the conversion of given substrate at a faster pase. |
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Sharkey, K. M., Carskadon, M. A., Figueiro, M. G., Zhu, Y., & Rea, M. S. (2011). Effects of an advanced sleep schedule and morning short wavelength light exposure on circadian phase in young adults with late sleep schedules. Sleep Med, 12(7), 685–692.
Abstract: OBJECTIVE: We examined the effects of an advanced sleep/wake schedule and morning short wavelength (blue) light in 25 adults (mean age+/-SD=21.8+/-3 years; 13 women) with late sleep schedules and subclinical features of delayed sleep phase disorder (DSPD). METHODS: After a baseline week, participants kept individualized, fixed, advanced 7.5-h sleep schedules for 6days. Participants were randomly assigned to groups to receive “blue” (470nm, approximately 225lux, n=12) or “dim” (<1lux, n=13) light for 1h after waking each day. Head-worn “Daysimeters” measured light exposure; actigraphs and sleep diaries confirmed schedule compliance. Salivary dim light melatonin onset (DLMO), self-reported sleep, and mood were examined with 2x2 ANOVA. RESULTS: After 6days, both groups showed significant circadian phase advances, but morning blue light was not associated with larger phase shifts than dim-light exposure. The average DLMO advances (mean+/-SD) were 1.5+/-1.1h in the dim light group and 1.4+/-0.7h in the blue light group. CONCLUSIONS: Adherence to a fixed advanced sleep/wake schedule resulted in significant circadian phase shifts in young adults with subclinical DSPD with or without morning blue light exposure. Light/dark exposures associated with fixed early sleep schedules are sufficient to advance circadian phase in young adults.
Keywords: Affect/physiology/radiation effects; Circadian Rhythm/*physiology/*radiation effects; Color; Dose-Response Relationship, Radiation; Female; Humans; *Light; Male; Melatonin/metabolism; Photoperiod; Phototherapy/*methods; Saliva/metabolism; Sleep/physiology/radiation effects; Sleep Disorders, Circadian Rhythm/prevention & control/*therapy; Stress, Psychological/prevention & control/therapy; Treatment Outcome; Young Adult; blue light
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Sinam, B., Sharma, S., Thakurdas, P., & Joshi, D. S. (2012). Bright photophase accelerates re-entrainment after experimental jetlag in Drosophila. Naturwissenschaften, 99(7), 575–578.
Abstract: The efficacy of bright photophase (BP) in accelerating the re-entrainment of Drosophila biarmipes rhythm following 8 h phase advance and delay of light-dark (LD) cycle was examined by subjecting the flies to 24 h LD cycles with dim photophase (DP) at 30 lx and BP at 300 lx. Re-entrainment was analysed by using the activity onset, activity offset and the duration of activity. Following LD advance or delay, the BP flies re-entrained faster than the DP flies which was attributed to the enhanced zeitgeber strength of BP. Nevertheless, the re-entrainment was a protracted process even in the BP flies since the activity offsets underwent more transients than the activity onsets. Thus, this study demonstrates that the BP accelerates the re-entrainment in D. biarmipes. It, however, also reveals that the re-entrainment is a prolonged process when the activity onset and offset are regarded as the rhythm markers.
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Summa, K. C., Vitaterna, M. H., & Turek, F. W. (2012). Environmental perturbation of the circadian clock disrupts pregnancy in the mouse. PLoS One, 7(5), e37668.
Abstract: BACKGROUND: The circadian clock has been linked to reproduction at many levels in mammals. Epidemiological studies of female shift workers have reported increased rates of reproductive abnormalities and adverse pregnancy outcomes, although whether the cause is circadian disruption or another factor associated with shift work is unknown. Here we test whether environmental disruption of circadian rhythms, using repeated shifts of the light:dark (LD) cycle, adversely affects reproductive success in mice. METHODOLOGY/PRINCIPAL FINDINGS: Young adult female C57BL/6J (B6) mice were paired with B6 males until copulation was verified by visual identification of vaginal plug formation. Females were then randomly assigned to one of three groups: control, phase-delay or phase-advance. Controls remained on a constant 12-hr light:12-hr dark cycle, whereas phase-delayed and phase-advanced mice were subjected to 6-hr delays or advances in the LD cycle every 5-6 days, respectively. The number of copulations resulting in term pregnancies was determined. Control females had a full-term pregnancy success rate of 90% (11/12), which fell to 50% (9/18; p<0.1) in the phase-delay group and 22% (4/18; p<0.01) in the phase-advance group. CONCLUSIONS/SIGNIFICANCE: Repeated shifting of the LD cycle, which disrupts endogenous circadian timekeeping, dramatically reduces pregnancy success in mice. Advances of the LD cycle have a greater negative impact on pregnancy outcomes and, in non-pregnant female mice, require longer for circadian re-entrainment, suggesting that the magnitude or duration of circadian misalignment may be related to the severity of the adverse impact on pregnancy. These results explicitly link disruptions of circadian entrainment to adverse pregnancy outcomes in mammals, which may have important implications for the reproductive health of female shift workers, women with circadian rhythm sleep disorders and/or women with disturbed circadian rhythms for other reasons.
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Titulaer, M., Spoelstra, K., Lange, C. Y. M. J. G., & Visser, M. E. (2012). Activity patterns during food provisioning are affected by artificial light in free living great tits (Parus major). PLoS One, 7(5), e37377.
Abstract: Artificial light may have severe ecological consequences but there is limited experimental work to assess these consequences. We carried out an experimental study on a wild population of great tits (Parus major) to assess the impact of light pollution on daily activity patterns during the chick provisioning period. Pairs that were provided with a small light outside their nest box did not alter the onset, cessation or duration of their working day. There was however a clear effect of artificial light on the feeding rate in the second half of the nestling period: when provided with artificial light females increased their feeding rate when the nestlings were between 9 and 16 days old. Artificial light is hypothesised to have affected the perceived photoperiod of either the parents or the offspring which in turn led to increased parental care. This may have negative fitness consequences for the parents, and light pollution may thus create an ecological trap for breeding birds.
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