History Dependence of Insect Circadian Rhythms History Dependence of Insect Circadian Rhythms 97 (original) (raw)
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Journal of Comparative Physiology B, 2012
Many physiological functions of insects show a rhythmic change to adapt to daily environmental cycles. These rhythms are controlled by a multi-clock system. A principal clock located in the brain usually organizes the overall behavioral rhythms, so that it is called the ''central clock''. However, the rhythms observed in a variety of peripheral tissues are often driven by clocks that reside in those tissues. Such autonomous rhythms can be found in sensory organs, digestive and reproductive systems. Using Drosophila melanogaster as a model organism, researchers have revealed that the peripheral clocks are self-sustained oscillators with a molecular machinery slightly different from that of the central clock. However, individual clocks normally run in harmony with each other to keep a coordinated temporal structure within an animal. How can this be achieved? What is the molecular mechanism underlying the oscillation? Also how are the peripheral clocks entrained by light-dark cycles? There are still many questions remaining in this research field. In the last several years, molecular techniques have become available in nonmodel insects so that the molecular oscillatory mechanisms are comparatively investigated among different insects, which give us more hints to understand the essential regulatory mechanism of the multi-oscillatory system across insects and other arthropods. Here we review current knowledge on arthropod's peripheral clocks and discuss their physiological roles and molecular mechanisms. Keywords Circadian clock Á Clock gene Á Peripheral clock Á Molecular oscillation Á Entrainment Communicated by I.D. Hume.
Journal of Biological Rhythms, 1986
Three night-break experiment protocols were utilized in an attempt to help clarify the role of the circadian system in photoperiodic time measurement in the European corn borer, Ostrinia nubilalis. Larvae raised in a light-dark (LD) cycle consisting of 12 hr of light alternating with 12 hr of darkness (LD 12:12), at a constant temperature of 30°C, enter a state of arrested growth and development known as diapause . In the present research (Experiment 1), the induction of diapause was prevented by 1-hr light pulses that systematically scanned the dark phase of LD 12:12. Thus, the importance of 12 hr of uninterrupted darkness for maximal induction of diapause is stressed. The same experimental protocol applied to larvae already in diapause (Experiment 2), however, resulted in a bimodal curve of diapause termination. Although this result is consistent with the proposition that a nonperiodic hourglass timer underlies this event (Skopik and Takeda, 1986), it does not rule out the circadian system.
OBSERVATION OF THE CIRCADIAN BIORHyTHM IN SOME INSECTS GROuPS
The Circadian rhythms of several flyers’ insects, Hymenoptera, Lepidoptera and Diptera, were monitored in the field by means of a Malaise trap, modified to capture separately every 3 hours intervals. The analyzed data are the insects number observed during each time interval and accumulated over an averaged trap operation of a few days. The Gaussian statistical distribution fit satisfactory the observed data, thus improving the precision in the determination of peak activity and the time- span of biorhythms. From the peak value and Gaussian width, the daily rhythm of each group can be accurately investigated. As a general result, all studied diurnal insects are active with the maximum in the early afternoon (about 14.00 hours after midnight), for duration of about 6-8 hours.
The hormonal and circadian basis for insect photoperiodic timing
FEBS Letters, 2011
Daylength perception in temperate zones is a critical feature of insect life histories, and leads to developmental changes for resisting unfavourable seasons. The role of the neuroendocrine axis in the photoperiodic response of insects is discussed in relation to the key organs and molecules that are involved. We also discuss the controversial issue of the possible involvement of the circadian clock in photoperiodicity. Drosophila melanogaster has a shallow photoperiodic response that leads to reproductive arrest in adults, yet the unrivalled molecular genetic toolkit available for this model insect should allow the systematic molecular and neurobiological dissection of this complex phenotype.
Evolutionary Links Between Circadian Clocks and Photoperiodic Diapause in Insects
Integrative and Comparative Biology, 2013
In this article, we explore links between circadian clocks and the clock involved in photoperiodic regulation of diapause in insects. Classical resonance (Nanda-Hamner) and night interruption (Bünsow) experiments suggest a circadian basis for the diapause response in nearly all insects that have been studied. Neuroanatomical studies reveal physical connections between circadian clock cells and centers controlling the photoperiodic diapause response, and both mutations and knockdown of clock genes with RNA interference (RNAi) point to a connection between the clock genes and photoperiodic induction of diapause. We discuss the challenges of determining whether the clock, as a functioning module, or individual clock genes acting pleiotropically are responsible for the photoperiodic regulation of diapause, and how a stable, central circadian clock could be linked to plastic photoperiodic responses without compromising the clock's essential functions. Although we still lack an understanding of the exact mechanisms whereby insects measure day/ night length, continued classical and neuroanatomical approaches, as well as forward and reverse genetic experiments, are highly complementary and should enable us to decipher the diverse ways in which circadian clocks have been involved in the evolution of photoperiodic induction of diapause in insects. The components of circadian clocks vary among insect species, and diapause appears to have evolved independently numerous times, thus, we anticipate that not all photoperiodic clocks of insects will interact with circadian clocks in the same fashion.
Insect timing (rhythms) from the point of view of neuroendocrine effector mechanisms
Acta Phytopathologica et Entomologica Hungarica, 2009
Living organisms, including insects, have developed a complex array of physiological and behavioral mechanisms allowing them to cope with biotic and abiotic challenges. Under natural circumstances they are readily capable to make 'predictions' and consequently can adjust their physiology and behavior to 'anticipate' the expected changes. The compilation of predictions provide a fine tuning to prepare for would-be conditions allowing them to react at the right time by the best set of available physiological, behavioral 'answers'. The attained internal harmony of the organism is the best option what an individual may achieve. Among insects, the most significant controller of rhythms is light and its changes, while temperature, humidity, food availability and population densities are also important. Rhythmic events at individual and population levels may be grouped as follows: development, dormant, reproductive, behavioral, metabolic cycles and polymorphism. The periodic changing of light and biological events related to this provides the most elaborate model. The main elements are: photoreception; clock mechanism measuring day and/or night length; photoperiodic counter including memory to accumulate information; neuroendocrine effector mechanisms regulating relevant physiological processes. A description of elements and an inventory will be provided of respective hormones, neuropeptides which are notably taking part in controlling events.
Journal of Insect Physiology, 2000
The last-instar larvae of a drosophilid fly, Chymomyza costata enter diapause in response to the dark-phases longer than 9 h (Yoshida, T., Kimura, M.T., 1995. The photoperiodic clock in Chymomyza costata. Journal of Insect Physiology 41, 217-222). In order to switch the developmental programming of the sensitive larvae from continuous development to diapause, after they were transferred from the short (8 h) to the long (14 h) dark-phase, significantly less time (1-2 days) was required when the dark-phase was abruptly and asymmetrically extended into the evening, than when it was extended symmetrically into both morning and evening (2-3 days), or asymmetrically into the morning hours (4-6 days). Diapause was also induced in 40-70% of sensitive larvae that were reared under the gradually shortening light-phase (from 16 h to 2 h, by 1 h in each cycle), despite that the dark-phase remained constant and short (8 h). Larvae developed continuously, however, when reared under the gradually extending light-phase (from 16 h to 24 h) and a constantly short dark-phase. We interpret such results, with the help of the two-oscillator model of circadian rhythmicity (Pittendrigh, C.S., Daan, S., 1976. A functional analysis of circadian pacemakers in nocturnal rodents. V. Pacemaker structure: A clock for all seasons. Journal of Comparative Physiology A 106, 333-355), as indicating that two mutually coupled oscillators (evening and morning) differing in their entrainability may participate in measuring of the dark-phase duration. The levels of dopamine (DA) and serotonin (5-HT) in the larval CNS transiently increased (by up to 20%) after the dusk, while no apparent change was observed during the dawn. The dusk-related increase was observed also after the asymmetric extension of the dark-phase into evening, while the asymmetric extension into morning had no effect on the levels of the DA and 5-HT.
Flies by NightEffects of Changing Day Length on Drosophila's Circadian Clock
Current Biology, 2004
morning and evening peaks, the locomotor activity has a strong tendancy to be bimodal [3, 8]. In the current Seattle, Washington 98195 2 Department of Biology and "seasonal-change" experiments, however, secondary peaks were also evident (Table 1). Under long night National Science Foundation Center for Biological Timing lengths (Ն12 hr), morning locomotor activity began late in the night, and peaks typically coincided with lights-Brandeis University Waltham, Massachusetts 02454 on. However, the presence of a peak about 2 hr before lights-on is evident in addition to the stronger peak associated with lights-on that predominates in the mean (Table 1). We were especially interested in the evening peak Summary because this locomotor maximum persists when flies are transferred from an LD cycle into DD, whereas the In Drosophila, two intersecting molecular loops constimorning peak typically disappears (reviewed in [3]). The tute an autoregulatory mechanism that oscillates with evening peak coincided with lights-off when day length a period close to 24 hr [1, 2, 3]. These loops touch when was less than 12 hr, and it anticipated lights-off as dayproteins from one loop, PERIOD (PER) and TIMELESS length increased. Thus, in LD 14:10, the peak occurred (TIM), repress the transcription of their parent genes, about 1 hr earlier than lights-off; in LD 16:8, it occurred period (per) and timeless (tim), by blocking positive 1.0-2.0 hr earlier, and in LD 18:6 it occurred about 3.5 transcription factors from the other loop. The arrival hr earlier (Figures 1E, 1F, and 1G). Under the shortest of PER and TIM into the nucleus of a clock cell marks nights, the evening peak appeared to stabilize at about the timing of this interaction between the two loops 14.0-14.5 hr after lights-on. [4]; thus, control of PER:TIM nuclear accumulation is a central component of the molecular model of clock PER and TIM Levels Adjust to Photoperiod function [1, 2, 3]. If a light pulse occurs early in the We analyzed the effects of day-length on temporal pronight as the heterodimer accumulates in the nucleus files of PER and TIM nuclear accumulation within key of clock cells, TIM is degraded, PER is destabilized, pacemaker neurons, the LN v 's, which express per and and clock time is delayed [1, 2, 3]. Alternatively, if TIM tim along with the Pigment dispersing factor (Pdf) gene is degraded during the later part of the night, after peak and the neuropeptide it encodes ([9]; LN v 's are reviewed accumulation, clock time advances. Current models in [3, 10, 11]). There are two classes of cells included in state that the effect of a light pulse depends on the the LN v 's: small and large. With one exception (see Figstate of the PER:TIM oscillation, which turns on the ure 4), we saw no differences between the relative prochanging levels of TIM. However, previous studies files of PER and TIM accumulation in these cell types have shown that light:dark (LD) regimes mimicking (data not shown). Therefore, we will emphasize the small seasonal changes cause behavioral adjustments while cells, in part because of their known relevance to behavaltering clock gene expression [5, 6]. This should be ioral rhythmicity [3]. reflected in the adjustment of PER and TIM dynamics. To evaluate possible differences between the nuclear We manipulated LD cycles to assess the effects of accumulation of PER and TIM in the LN v 's, we conaltered day length on PER and TIM dynamics in clock structed detailed time courses of their expression under cells within the central brain as well as light-induced LD 8:16 and LD 16:8. Although a weak nuclear TIM signal resetting of locomotor rhythms. was detectable under LD 8:16 4-6 hr after lights-off, the cytoplasmic signal was far greater (Figures 1A and 1B). Clear nuclear accumulation of TIM in LD 8:16 was evi-Results dent 8 hr after lights-off (Figures 2A and 2B). Peak levels of nuclear TIM accumulation occurred 10 hr after lights-Locomotor Activity Adjusts to Photoperiod As day length varies within a 24 hr LD cycle, mammals off and decreased to undetectable baseline levels by 2 hr after lights-on (Figures 1A and 1B). This profile of TIM and insects display a correlated adjustment in peak nuclear accumulation under LD 8:16 is similar to that observed under LD 12:12 conditions [12].
Journal of Biological Rhythms, 2007
Photoperiodic regulation of development requires a timing mechanism to distinguish long days from short days (a photoperiodic clock), a mechanism to count the number of long or short days (a counter), and endocrine outputs governing the final expression of the developmental mode (diapause vs. continuous development or reproduction) (Denlinger, 2002; Saunders, 2002). A substantial body of evidence suggests that night-length measurement is a function of the circadian system (Saunders et al., 2004; Saunders, 2005). A potential role of circadian clock genes in photoperiodism is the subject of extensive discussions (Tauber and Kyriacou, 2001; Saunders et al., 2004; Mathias et al., 2005). Remarkable progress has been made in the genetic dissection of the circadian clock in Drosophila melanogaster (Dunlap, 1999; Panda et al., 2002).
Possible ?dawn? and ?dusk? roles of light pulses shifting the phase of a circadian rhythm
Journal of Comparative Physiology, 1973
A new automatic photoelectric method used in recording the eclosion rate of flies is described. The phase responses of the circadian rhythm of eclosion in Drosophila pseudoobscura to light pulses, of 1000 lx intensity and durations varying between 30 min and 12 h, were studied. The rhythm responds selectively either to the "on" or to the "off" transition of light pulses offered during the subjective night. The light pulses shift phase with the "off" transition during the first half of the night (dusk effect) and shift phase with the "on" transition during the second half of the night (dawn effect). The present findings are briefly discussed in the context of the work of other authors in this field.