@article{VazeHelfrichFoerster2016,
  author    = {Vaze, Koustubh M. and Helfrich-F{\"o}rster, Charlotte},
  title     = {Drosophila ezoana uses an hour-glass or highly damped circadian clock for measuring night length and inducing diapause},
  series = {Physiological Entomology},
  volume    = {41},
  journal   = {Physiological Entomology},
  number    = {4},
  doi       = {10.1111/phen.12165},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204278},
  pages     = {378-389},
  year      = {2016},
  abstract  = {Insects inhabiting the temperate zones measure seasonal changes in day or night length to enter the overwintering diapause. Diapause induction occurs after the duration of the night exceeds a critical night length (CNL). Our understanding of the time measurement mechanisms is continuously evolving subsequent to B{\"u}nning's proposal that circadian systems play the clock role in photoperiodic time measurement (B{\"u}nning, 1936). Initially, the photoperiodic clocks were considered to be either based on circadian oscillators or on simple hour-glasses, depending on 'positive' or 'negative' responses in Nanda-Hamner and B{\"u}nsow experiments (Nanda \& Hammer, 1958; B{\"u}nsow, 1960). However, there are also species whose responses can be regarded as neither 'positive', nor as 'negative', such as the Northern Drosophila species Drosophila ezoana, which is investigated in the present study. In addition, modelling efforts show that the 'positive' and 'negative' Nanda-Hamner responses can also be provoked by circadian oscillators that are damped to different degrees: animals with highly sustained circadian clocks will respond 'positive' and those with heavily damped circadian clocks will respond 'negative'. In the present study, an experimental assay is proposed that characterizes the photoperiodic oscillators by determining the effects of non-24-h light/dark cycles (T-cycles) on critical night length. It is predicted that there is (i) a change in the critical night length as a function of T-cycle period in sustained-oscillator-based clocks and (ii) a fxed night-length measurement (i.e. no change in critical night length) in damped-oscillator-based clocks. Drosophila ezoana flies show a critical night length of approximately 7 h irrespective of T-cycle period, suggesting a damped-oscillator-based photoperiodic clock. The conclusion is strengthened by activity recordings revealing that the activity rhythm of D. ezoana flies also dampens in constant darkness.},
  language  = {en}
}
@article{AmatobiOzbekUnalSchaebleretal.2023,
  author    = {Amatobi, Kelechi M. and Ozbek-Unal, Ayten Gizem and Sch{\"a}bler, Stefan and Deppisch, Peter and Helfrich-F{\"o}rster, Charlotte and Mueller, Martin J. and Wegener, Christian and Fekete, Agnes},
  title     = {The circadian clock is required for rhythmic lipid transport in Drosophila in interaction with diet and photic condition},
  series = {Journal of Lipid Research},
  volume    = {64},
  journal   = {Journal of Lipid Research},
  number    = {10},
  doi       = {10.1016/j.jlr.2023.100417},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-349961},
  pages     = {100417},
  year      = {2023},
  abstract  = {Modern lifestyle is often at odds with endogenously driven rhythmicity, which can lead to circadian disruption and metabolic syndrome. One signature for circadian disruption is a reduced or altered metabolite cycling in the circulating tissue reflecting the current metabolic status. Drosophila is a well-established model in chronobiology, but day-time dependent variations of transport metabolites in the fly circulation are poorly characterized. Here, we sampled fly hemolymph throughout the day and analyzed diacylglycerols (DGs), phosphoethanolamines (PEs) and phosphocholines (PCs) using LC-MS. In wild-type flies kept on sugar-only medium under a light-dark cycle, all transport lipid species showed a synchronized bimodal oscillation pattern with maxima at the beginning and end of the light phase which were impaired in period01 clock mutants. In wild-type flies under constant dark conditions, the oscillation became monophasic with a maximum in the middle of the subjective day. In strong support of clock-driven oscillations, levels of the targeted lipids peaked once in the middle of the light phase under time-restricted feeding independent of the time of food intake. When wild-type flies were reared on full standard medium, the rhythmic alterations of hemolymph lipid levels were greatly attenuated. Our data suggest that the circadian clock aligns daily oscillations of DGs, PEs, and PCs in the hemolymph to the anabolic siesta phase, with a strong influence of light on phase and modality.},
  language  = {en}
}