TY  - JOUR
A1  - Vaze, Koustubh M.
A1  - Helfrich-Förster, Charlotte
T1  - Drosophila ezoana uses an hour-glass or highly damped circadian clock for measuring night length and inducing diapause
T2  - Physiological Entomology
N2  - 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 Bünning’s proposal that circadian systems play the clock role in photoperiodic time measurement (Bünning, 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 Bünsow experiments (Nanda & Hammer, 1958; Bünsow, 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.
KW  - photoperiodic time mesurement
KW  - wyeomyia smithii
KW  - protophormia terraenovae
KW  - immunoreactive neurons
KW  - geographical variation
KW  - reproductive diapause
KW  - rhythmic components
KW  - locomotor activity
KW  - circadian clock
KW  - damped-oscillator-model of photoperiodic clock
KW  - diapause
KW  - Drosophila
KW  - hour-glass
KW  - pitcher-plant mosquito
KW  - bug riptortus-pedestris
KW  - Nanda-Hamner
KW  - photoperiodism
Y1  - 2016
UR  - https://opus.bibliothek.uni-wuerzburg.de/frontdoor/index/index/docId/20427
UR  - https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-204278
VL  - 41
IS  - 4
ER  -