Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua

The influence of pupal diapause on adult eclosion rhythm of Delia antiqua was investigated. When non-diapause and diapause pupae were exposed to various photoperiods at 15, 20 and 25 °C, both of them emerged as adults close to the light-on time, but the phase of eclosion varied with photoperiod and temperature. Moreover, there was a significant difference in the eclosion time between non-diapause and diapause pupae; the eclosion peak of diapause pupae was earlier than that of non-diapause pupae. When non-diapause and diapause pupae were transferred to constant darkness (DD) after having experienced LD 12:12 at 15, 20 and 25 °C, both showed circadian rhythmicity in eclosion. Although the free-running period (τ) decreased slightly as temperature increased in both non-diapause and diapause pupae, the latter tended to show shorter τ than the former. This observation suggests that the observed difference in eclosion time in LD cycles between non-diapause and diapause pupae is due to differences in τ.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the change of rhythmicity

When pupae of Delia antiqua were transferred to constant darkness (DD) from light-dark (LD) cycles or constant light (LL), the sensitivity to light of the circadian clock controlling eclosion increased with age. The daily rhythm of eclosion appeared in both non-diapause and diapause pupae only when this transfer was made during late pharate adult development. When transferred from LL to DD in the early pupal stage, the adult eclosion was weakly rhythmic in non-diapause pupae but arrhythmic in diapause pupae. However, the sensitivity of the circadian clock to temperature cycles or steps was higher in diapause pupae than in non-diapause pupae; in the transfer to a constant 20 degrees C from a thermoperiod of 25 degrees C (12 h)/20 degrees C (12 h) on day 10 after pupation or from chilling (7.5 degrees C) in DD, the adult eclosion from diapause pupae was rhythmic but that from non-diapause pupae arrhythmic. In a transfer to 20 degrees C from the thermoperiod after the initiation of eclosion, rhythmicity was observed in both types of pupae. The larval stage was insensitive to the effect of LD cycle initiating the eclosion rhythm. In D. antiqua pupae in the soil under natural conditions, therefore, the thermoperiod in the late pupal stage would be the most important 'Zeitgeber' for the determination of eclosion timing.     

Thermoperiodic regulation of the circadian eclosion rhythm in the flesh fly, Sarcophaga crassipalpis

We recorded the eclosion time of the flesh fly, Sarcophaga crassipalpis, at different depths in the outdoor soil and under temperature cycles with various amplitudes in the laboratory, to examine the timing adjustment of eclosion in response to temperature cycles and their amplitudes in the pupal stage. In the soil, most eclosions occurred in the late morning, which was consistent with the eclosion time under pseudo-sinusoidal temperature cycles in the laboratory. The circadian clock controlling eclosion was reset by temperature cycles and free-ran with a period close to 24 h. This clock likely helps pupae eclose at an optimal time even when the soil temperature does not show clear daily fluctuations. The eclosion phase of the circadian clock progressively advanced as the amplitude of the pseudo-sinusoidal temperature cycle decreased. This response allows pupae located at any depth in the soil to eclose at the appropriate time despite the depth-dependent phase delay of the temperature change. In contrast, the abrupt temperature increase in square-wave temperature cycles reset the phase of the circadian clock to the increasing time, regardless of the temperature amplitude. The rapid temperature increase may act as the late-morning signal for the eclosion clock.     

Effect of photoperiod and thermoperiod on the eclosion rhythm ofTrichogramma evanescens

The dynamics of adult eclosion inTrichogramma evanescens Westw. were studied under (1) constant light and temperature of 20 °C, (2) photoperiods L12:D12 and L16:D8 at 20 °C, (3) thermoperiod 4 h 27 °/20 h 20 °C at constant light, (4) joint action of photo- and thermoperiod. The emergence was arhythmic in constant light combined with constant temperature, while a sharp monophasic rhythm was observed with the isolated action of photo- or thermoperiod. The ‘light-on’ and ‘temperature step-up’ signals were shown to act in one direction. When both signals were combined, they manifested themselveses competing entraining stimuli which, in turn, revealed an apparent individual variation in relative reactivity to the light and temperature signals. Some perspectives which follow from these observations are discussed.     

Effects of temperature, photoperiod, and light intensity on the eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae

Eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae from Badrinath (altitude 5123 m) was temperature-dependent and at 21°C, it was entrained by cycles of 12 h light: 12 h darkness (LD 12:12) and free-ran in constant darkness, however, it was arrhythmic at 13°C or 17°C under identical experimental conditions (Khare, P. V., Barnabas, R. J., Kanojiya, M., Kulkarni, A. D., Joshi, D. S. (2002). Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae. Chronobiol. Int. 19:1041-1052). The present studies were designed to see whether or not these strains could be entrained at 13°C, 17°C, and 21°C by two types of LD cycles in which the photoperiod at 100 lux intensity varied from 6 h to 18 h, and the light intensity of LD 14:10 cycles varied from 0.001 lux to 1000 lux. All LD cycles entrained this strain at 21°C but not at 13°C or 17°C. These results demonstrate that the entrainment of eclosion rhythm depends on the ambient temperature and not on the photoperiod or light intensity of LD cycles. Thus the temperature has taken precedence over the light in the entrainment process of eclosion rhythm of the high altitude Himalayan strain of D. ananassae. This may be the result of natural selection in response to the environmental temperature at Badrinath that resembles that of the sub-Arctic region but the photoperiod or light intensity are of the subtropical region.     

In vitro regulation of circadian phosphorylation rhythm of cyanobacterial clock protein KaiC by KaiA and KaiB

Biochemical circadian oscillation of KaiC phosphorylation, by mixing three Kai proteins and ATP, has been proven to be the central oscillator of the cyanobacterial circadian clock. In vivo, the intracellular levels of KaiB and KaiC oscillate in a circadian fashion. By scrutinizing KaiC phosphorylation rhythm in a wide range of Kai protein concentrations, KaiA and KaiB were found to be “parameter-tuning” and “state-switching” regulators of KaiC phosphorylation rhythm, respectively. Our results also suggest a possible entrainment mechanism of the cellular circadian clock with the circadian variation of intracellular levels of Kai proteins.     

Clock genes period and timeless are rhythmically expressed in brains of newly hatched, photosensitive larvae of the fly, Sarcophaga crassipalpis

While roles of the clock genes period (per) and timeless (tim) are relatively well understood in relation to circadian clocks, their potential roles in insect photoperiodism remain enigmatic. In this study, the expression of per and tim genes under two contrasting photoperiods is described in the central nervous system of photoperiodically sensitive, newly hatched first instar larvae of the flesh fly, Sarcophaga crassipalpis. Using qPCR, diel oscillations were observed in the mRNA levels of both genes under long-day (15 h light:9 h dark, promotes direct development) and short-day conditions (11 h light:13 h dark, induces pupal diapause). Peak per and tim mRNA oscillations were closely associated with the light/dark transition. The conspicuous difference between the two photoperiodic conditions was that the sharp increase in per and tim mRNA abundance occurred during the light phase under long days but during the dark phase under short days. The diel oscillations were, at least in part, driven by an endogenous component, as demonstrated by transferring larvae to continuous darkness. The cells displaying Tim- and Per-like immunoreactivities (Tim- and Per-LIRs) were localized using anti-Drosophila-Per and anti-Chymomyza-Tim antibodies. Per-LIR and Tim-LIR co-localized in three groups of cells in each brain hemisphere. Two other groups, one in the brain hemispheres and the other in the fused ventral nerve ganglion, expressed only the Per-LIR.     

Seasonal change in the locomotor activity rhythm of the medaka,Oryzias latipes

A group of the medaka,Oryzias latipes (Cyprinodontidae, orange-red variety, 25 males and 25 females), was kept in an aquarium, which was placed outdoors under natural conditions from December 1984 to January 1986. Locomotor activity at three layers (upper, middle, and lower layers) was recorded with a phototransistor system in each season. In summer, the fish showed typical diurnal activity at all three layers and the activity was greater than in other seasons. However, in autumn and winter, the fish became less active and showed relatively high activity at night at the upper or middle layer and diurnal activity at the lower layer. Nocturnal activity seemed to appear when the water temperature was decreased and the photoperiod was shortened. A free-running activity rhythm was also recorded under continuous darkness (DD) in each season; however, the fish showed clear free-running activity rhythms under DD only in summer.     

Circadian rhythms of adult emergence and activity but not eclosion in males of the parasitic wasp Nasonia vitripennis

An endogenous circadian system is responsible for the rhythms observed in many physiological and behavioural traits in most organisms. In insects, the circadian system controls the periodicity of eclosion, egg-laying, locomotor and mating activity. The parasitoid wasp Nasonia vitripennis has been extensively used to study the role of the circadian system in photoperiodism. In this study, behavioural activities expected to be under the control of the endogenous circadian system were characterized in Nasonia. Male emergence from the host puparium is rhythmic under light-darkness conditions while eclosion from the own pupal integument is not rhythmic but continuous. Following entrainment in light-dark conditions, males show robust free-running circadian activity rhythms with a period (τ, tau) of approximately 25.6 h in constant darkness. While the endogenous circadian system is enough to trigger male emergence in Nasonia, light seems to have a modulatory effect: when present it induces more males to emerge. Our results add to the understanding of chronobiological phenotypes in insects and provide a basis towards the molecular characterization of the endogenous circadian system in Nasonia.     

Circadian rhythm in plasma aldosterone concentration and its seasonal modulation in the camel (Camelus dromedarius) living in the Algerian Sahara desert

Five male camels dwelling in the Algerian Sahara were studied for circadian rhythmicity in plasma aldosterone concentration and its seasonal modulation. Blood was sampled at a frequency of 1 h or less for a span of 27 h during each season of the year. The mean plasma aldosterone concentration exhibited a significant circadian rhythmicity in every season of the year. Plasma aldosterone concentration was lowest in the morning, increased in the afternoon, and generally highest in the late evening. The peak of the circadian rhythm exhibited seasonal variation; it occurred at 20:04h in October, 16:41h in December, 20:40h in March, and 24:16h in June. The rhythm's 24h mean also exhibited seasonal variability, being significantly higher in March and June compared to October.     

A study of the relationship between photoperiod and pinealocyte granulated vesicles in the golden Syrian hamster

Summary Previous studies in rabbits and mice have revealed distinct circadian rhythms in the number of pinealocyte granulated vesicles (PGVs) and control of their synthesis and/or secretion by sympathetic nerves. The present study demonstrates the absence of a circadian rhythm in PGV content in hamsters functionally pinealectomized by maintenance under long photoperiod (L/D=14/10 h). On the other hand, a highly significant rhythm of low amplitude was noted in PGVs of hamsters placed in photoperiods (<12.5 h) which are known to initiate pineal antigonadotropic activity. Bilateral optic enucleation, which also leads to pineal-mediated gonadal atrophy in the hamster, produced a significant decrease in the number of perivascular PGVs when compared to intact control animals. Daily late afternoon injections of melatonin produced no significant difference in the number of PGVs between treated and control animals at any sample time examined.Supported in part by N.I.H. Grant#HD08759     

Influence of temperature changes on larviposition rhythm in the tsetse fly, Glossina morsitans

ABSTRACT. The hourly and quarter-hourly distribution of larval deposition by female Glossina morsitans Westw. was studied at various temperatures. At constant temperature and humidity, peak larviposition occurred 8–9 h after lights on. The effect of confining the flies to daily (LD 12:12 h) regimes of at least twenty-five consecutive cycles that included a sudden increase in temperature of c. 6°C for 2 h was a significant reduction in depositions during each period of increased temperature, and a significant increase before the heat impulse. When the temperature was allowed to fall rapidly, larviposition rate doubled in the following 15 min.     

Visual behaviour of the onion fly, Delia antiqua: antagonistic interaction of ultraviolet and visible wavelength reflectance

The interaction of ultraviolet (UV=350–400 nm) and visible (VISIBLE=400–650 nm) wavelengths in the visual behaviour of the onion fly, Delia antiqua (Meigen), was examined by measuring spontaneous alightment on various UV- and non-UV-reflecting, sticky cardboard traps in onion fields. Alightment on traps was negatively correlated with the percent UV (350 nm) and green (540–580 nm) reflectance and positively correlated with the percent blue (430–470 nm) reflectance. Alightment varied directly with the ratio of stimulatory/inhibitory reflected wavelengths. Males and females were similar in their response to both UV and VISIBLE wavelength reflectance, with the exception that males were more sensitive than females to UV-reflecting white surfaces. A multiple regression model, that used the intensity of 3 key wavelengths, 350, 450 and 560 nm, as independent variables, explained 90% of the variation in the combined male and female response to spectral reflectance from traps. These results indicate that some visual behaviours of D. antiqua are a function of the integration of sensory input from the entire spectral distribution of the stimulus, and not simply the dominant wavelengths or hue.

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Résumé L'interaction des ondes ultraviolettes (UV=350–400 n nm) et des ondes visibles (VISIBLE=400–650 nm) sur le fonctionnement visuel de la mouche de l'oignon, Delia antiqua, a été examinée par le mesurage des descentes spontanées sur des pièges variés, construits de carton gluant, qui reflète le UV ou non, dans des champs d'oignons. Les descentes furent en rapport négativement avec le pour-cent de la réflexion de l'UV (350 nm) et du vert (540–580 nm), et en rapport positivement avec la réflexion du bleu (430–470 nm). Le chiffre des descentes était en rapport directement avec la porportion stimulantes/inhibitantes des ondes reflétées. Les mâles et les femelles étaent comparables en leurs réponses aux ondes UV et VISIBLES reflétées, sauf que les mâles fussent plus sensibles que les femelles aux surfaces blanches et UV-reflétantes. Une modèle d'analyse multiple de regression qui prenait en considération les intensités des trois ondes significatives, 350, 450 et 560 nm, en tant que les variables indépendants, a expliqué 90% de la variation en la réponse combinée des mâles et des femelles à la réflexion spectrale des pièges. Ces resultats indiquent que quelques fonctionnements visuels de la D. antiqua sont une fonction des données sensorielles de la distribution spectrale entière du stimulus, pas seulement une fonction des ondes dominantes ou de la teinte.

     

Clock-controlled rhythm of ecdysteroid levels in the haemolymph and testes, and its relation to sperm release in the Egyptian cotton leafworm, Spodoptera littoralis

In Spodoptera littoralis, testicular sperm release occurs in a daily rhythm, which is controlled by endogenous circadian oscillator located in the male reproductive system. Although this rhythm is essential for male fertility, factors that initiate and maintain daily sperm release are not understood. In this study, we investigated a modulatory role for ecdysteroids in the sperm release rhythm and identified the source of ecdysteroids in adult males. We found that the onset of sperm release occurs two days pre-eclosion and coincides with a significant decrease in haemolymph ecdysteroids levels. 20-HE injection into the pupae prior to the first sperm release delayed its initiation and disrupted the developing rhythm in a dose dependent manner. 20-HE injection into adults depressed the number of sperm bundles leaving the testes. A day before the initial sperm release, ecdysteroid levels in the haemolymph and testes begin to oscillate in a circadian fashion. Ecdysteroid rhythms continue throughout imaginal life and correlate with the rhythm of sperm release. In each cycle, testicular sperm release coincides with a trough in testicular ecdysteroid concentration. Rhythmic changes in ecdysteroid levels are regulated by an endogenous circadian oscillator that continues to function in decapitated males. The generation of a complete cycle of ecdysteroid release by testes cultured in vitro indicates that this oscillator is located in the gonads. The haemolymph ecdysteroid levels are significantly lower and arrhythmic in males with removed testes, indicating that the testes are an important ecdysteroid source that may contribute to oscillations in haemolymph ecdysteroid levels.     

Endogenous rhythms of locomotion in the American horseshoe crab, Limulus polyphemus

American horseshoe crabs (Limulus polyphemus) exhibit clear circadian rhythms of visual sensitivity in the laboratory and in the field they exhibit seasonal patterns of mating behavior that are closely associated with the tides. Recent reports suggest that Limulus locomotor activity may be controlled by endogenous circadian and/or circatidal clocks and that light:dark (LD) cycles may affect the rhythmic output of both of these clocks. In this study, we examined locomotor behavior in the laboratory to determine the extent of this endogenous activity and to examine the influence of LD cycles on these rhythms. Thirty-three L. polyphemus were captured during the breeding season and their activity was monitored with activity boxes and “running wheels” in seawater kept at constant temperature and salinity. Activity patterns were analyzed using visual inspection of actograms and Chi-square and Lomb-Scargle periodograms. Overall, 36% of the animals was significantly more active during L, while only 12% was more active during D (52% showed no preference). Circatidal rhythms were observed in LD in 67% of the horseshoe crabs. Surprisingly, LD cycles appeared to synchronize these rhythms at times. In DD, the majority of animals tested (63%) exhibited circatidal rhythms that persisted for at least seven days. Overall, the results demonstrate that an endogenously controlled tidal rhythm of locomotion operates during, and significantly after, the breeding season in this species. In addition, the present results are consistent with the presence of circalunidian oscillators controlling these rhythms.     

A circadian system is involved in photoperiodic entrainment of the circannual rhythm of Anthrenus verbasci

In the circannual pupation rhythm of the varied carpet beetle, Anthrenus verbasci, entrainment to annual cycles is achieved by phase resetting of the circannual oscillator in response to photoperiodic changes. In order to examine whether a circadian system is involved in expression of the periodic pattern and phase resetting of the circannual rhythm as photoperiodic responses, we exposed larvae to light-dark cycles with a short photophase followed by a variable scotophase (the Nanda-Hamner protocol). When the cycle length (T) was a multiple of 24 h, i.e., 24, 48, or 72 h, short-day effects were clearer than when T was far from a multiple of 24 h, i.e., 36 or 60 h. Exposure to light-dark cycles of T = 36 h had effects similar to exposure to long-day cycles of T = 24 h. The magnitude of phase shifts depended on the duration and the phase of exposure to the cycles of T = 36 or 60 h. It was therefore concluded that a circadian system is involved in photoperiodic time measurement for phase resetting of the circannual oscillator of A. verbasci.     

Photoperiodic modulation of circadian rhythms in the cricket Gryllus bimaculatus

The waveform and the free-running period of circadian rhythms in constant conditions are often modulated by preceding lighting conditions. We have examined the modulatory effect of variable length of light phase of a 24h light cycle on the ratio of activity (alpha) and rest phase (rho) as well as on the free-running period of the locomotor rhythm in the cricket Gryllus bimaculatus. When experienced the longer light phases, the alpha/rho-ratio was smaller and the free-running period was shorter. The magnitude of changes in alpha/rho-ratio was dependent on the number of cycles exposed, while the free-running period was changed by a single exposure, suggesting that there are separate regulatory mechanisms for the waveform and the free-running period. The neuronal activity of the optic lobe showed the alpha/rho-ratio changing with the preceding photoperiod. When different photoperiodic conditions were given to each of the two optic lobe pacemakers, the alpha/rho-ratio of a single pacemaker was rather intermediate between those of animals treated with either of the two conditions. These results suggest that the storage of the photoperiodic information occurs at least in part in the optic lobe pacemaker, and that the mutual interaction between the bilateral optic lobe pacemakers is involved in the photoperiodic modulation.     

Phaseshifting of the photoperiodic flowering response rhythm in Pharbitis nil by red-light pulses

The control by light of the flowering response rhythm in the short-day plant Pharbitis nil Choisy cv. Violet was examined by giving a single pulse of light at various times between 1 and 6 h after a 24-h light period. When the first circadian cycle of the rhythm was monitored, it was found that a pulse of red light given at 1, 2 or 3 h into a 72-dark period caused a 1-h delay of the phase of the response rhythm, while a pulse at 6 h caused a 2-h delay. These results support the hypothesis that, when red-light pulses are given at hourly intervals, they are as effective as continuous light in preventing the onset of dark timing because they repeatedly return the rhythm to the circadian time at which it is apparently suspended in continuous light. The perception of and response to continuous light and red-light pulses are also briefly discussed.