Effects of psi-mutations on the Oviposition Rhythm of Drosophila rajasekari

The psi -mutations affected the circadian rhythm of locomotor activity in the early and late strains of Drosophila rajasekari (Joshi, 1999a). The present study was designed to determine the effects of psi -mutations on the oviposition rhythm of the early and late strains. Oviposition rhythms were studied in light-dark cycles of 12 :12 h in which the light intensity of photophase was 0.001, 0.01, 0.1, 1, 10, 100 or 1000 lux. The oviposition rhythm of wild type was unimodal at or above 10 lux with a peak before lights-off, while it was bimodal at lower light intensities. The early strain was unimodal at all light intensities with a peak after lights-on at or above 10 lux, and around the mid-day at or below 1lux. The late strain was rhythmic at 100 and 1000 lux with a peak after the lights-off, weakly rhythmic at 10 lux and arrhythmic at or below 1 lux. Free running period in constant darkness was shortest in the early and longest in the late strain. Threshold light intensity of constant light to generate arrhythmicity was lowest in the early and highest in the late strain, apparently the photic sensitivity of the clock photoreceptors was differentially altered by these mutations. Thus the psi -mutations for locomotor rhythmicity affected the oviposition rhythm too, suggesting that the same circadian oscillator might be controlling these both rhythms.     

Rhythm-Specific Mutations in Drosophila rajasekari Altered Adult Locomotor Activity Rhythm but Not Eclosion Rhythm

The early and late strains for phase angle difference (Φ) of adult locomotor activity in Drosophila rajasekari were developed by artificial selection; these strains differed in Φ, activity pattern, activity level, free-running period (τ) in constant darkness (DD) and light induced phase shifts from those of the wild type (Joshi, 1998). The present studies were designed to determine whether or not the psi-mutations for adult locomotor activity rhythm had also altered the fundamental properties of the eclosion rhythms in these strains. The circadian rhythms of eclosion have been studied in the wild type, the early and late strains. In contrast to the effects on the locomotor activity rhythms in the early and late strains, the psi-mutations have no apparent effect on the eclosion median in light-dark cycles of 12 : 12 h, on τ in DD, light induced phase shifts or subjective light sensitivity in these strains. Thus the psi-mutations for the adult locomotor activity rhythms in D. rajasekari appear to be rhythm-specific mutations altering the locomotor rhythms but not the eclosion rhythms.     

Rhythm-Specific Mutations in Drosophila rajasekari Altered Adult Locomotor Activity Rhythm but Not Eclosion Rhythm

The early and late strains for phase angle difference (Φ) of adult locomotor activity in Drosophila rajasekari were developed by artificial selection; these strains differed in Φ, activity pattern, activity level, free-running period (τ) in constant darkness (DD) and light induced phase shifts from those of the wild type (Joshi, 1998). The present studies were designed to determine whether or not the psi-mutations for adult locomotor activity rhythm had also altered the fundamental properties of the eclosion rhythms in these strains. The circadian rhythms of eclosion have been studied in the wild type, the early and late strains. In contrast to the effects on the locomotor activity rhythms in the early and late strains, the psi-mutations have no apparent effect on the eclosion median in light-dark cycles of 12 : 12 h, on τ in DD, light induced phase shifts or subjective light sensitivity in these strains. Thus the psi-mutations for the adult locomotor activity rhythms in D. rajasekari appear to be rhythm-specific mutations altering the locomotor rhythms but not the eclosion rhythms.     

Effects of Photophase and Altitude on Oviposition Rhythm of the Himalayan Strains of Drosophila Ananassae

The effects of varying photophase and altitude of origin on the phase angle difference (Ψ) of the circadian rhythm of oviposition during entrainment to light‐dark (LD) cycles and the aftereffects of such photophases on the period of the free‐running rhythm (τ) in constant darkness (DD) were evaluated in two Himalayan strains of Drosophila ananassae, the high‐altitude (HA) strain from Badrinath (5,123 m above sea level=ASL) and the low‐altitude (LA) strain from Firozpur (179 m ASL). The Ψ (i.e., the hours from lights‐on of the LD cycle to oviposition median) of both strains was determined in LD cycles in which the photophase at 100 lux varied from 6 to 18 h/24 h. The HA strain was entrained by all LD cycles except the one with 6 h photophase in which it was weakly rhythmic, but the LA strain was entrained by only three LD cycles with photophases of 10, 12, and 14 h, but photophases of 6, 8, 16, and 18 h rendered it arrhythmic. Lights‐off transition of LD cycles was the phase‐determining signal for both strains as oviposition medians of the HA strain occurred～6 h prior to lights‐off, while those of the LA strain occurred～1 h after lights‐off. The Ψ of the HA strain increased from～2 h in 8 h photophase to～11 h in 18 h photophase, while that of the LA strain increased from～11 h in 10 h photophase to～15 h in 14 h photophase. The aftereffects of photophase of the prior entraining LD cycles on τ in DD were determined by transferring flies from LD cycles to DD. The τ of the HA strain increased from～19 to～25 h when transferred to DD from LD 8:16 and LD 18:6 cycles, respectively, whereas the τ of the LA strain increased from～26 to～28 h when transferred to DD from LD 10:14 and LD 14:10 cycles, respectively. Thus, these results demonstrate that the photophases of entraining LD cycles and the altitude of origin affected several parameters of entrainment and the period of the free‐running rhythm of these strains.     

Effect of Light Intensity on the Oviposition Rhythm of the Altitudinal Strains of Drosophila Ananassae

The sensitivity of the circadian photoreceptors mediating entrainment of the eclosion rhythm and phase shifts of oviposition rhythm of the high altitude (HA) strain of Drosophila ananassae originating from Badrinath (5123 m above sea level) in the Himalayas was compared with the low altitude (LA) strain from Firozpur (179 m above sea level). Reduced photic sensitivity of the HA strain is regarded as the result of natural selection, which led to the weakening of the coupling mechanism between the circadian pacemaker and light at the high altitude of origin. The present study was designed to determine whether or not the photic entrainment of the oviposition rhythm of the HA strain of D. ananassae is also altered by the high altitude of its origin, and the results are compared with those of the LA strain. The effects of light intensity on the phase angle difference (Ψ), degree of rhythmicity (R), the percent oviposition in photophase, the threshold light intensity (i.e., the intensity at which stable entrainment occurred), and the saturation light intensity (i.e., the intensity beyond which the values of Ψ or amplitude of rhythm remained unaltered) were determined. Entrainment was studied in light–dark cycles in which the light intensity of 12 h of photophase varied from 1 to 1000 lux, and complete darkness prevailed in all scotophases. The oviposition rhythm of the HA strain was arrhythmic from 1 to 90 lux, weakly rhythmic at 95 lux, but rhythmic at or above 100 lux, while that of the LA strain was weakly rhythmic at 1 lux but rhythmic at or above 2 lux. Oviposition of the HA strain occurred mostly in the photophase, while that of the LA strain occurred in the scotophase; as a result, the oviposition medians of the HA strain were around the subjective forenoons while those of the LA strain were around the subjective evenings. The percent of oviposition in photophase increased from 68 to 98 in the HA strain and from 5 to 33 in the LA strain as light intensity increased from 1 to 1000 lux. In the HA strain, the Ψ values were significantly less and values of R and percent oviposition in photophase were significantly more than those of the LA strain at each level of light intensity. Threshold and saturation intensities for Ψ were 100 and 700 lux, respectively, for the HA strain, but just 2 and 45 lux, respectively, for the LA strain. The saturation intensity for R was 650 and 700 lux for the HA and LA strains, respectively. These results extend the confirmation that the reduced photic sensitivity of the HA strain might have been acquired through natural selection in response to environmental conditions at the high altitude of its origin.     

影响野生型Canton S果蝇睡眠时间的相关生理因素

目的探讨影响果蝇睡眠时间的相关生理因素。方法选择野生型CantonS果蝇为实验对象,利用果蝇活动监测系统(DAMS),以5min为单位自动统计一次果蝇活动次数,若5min内活动次数为零,认为果蝇处于睡眠状态,计为果蝇的睡眠时间,累积计算果蝇24h睡眠总时间为指标,分别观察了日龄(7日龄)相同,而性别不同和性别(雌性)相同,而日龄(2,7,12,17,22,27和32日龄)不同果蝇的24h睡眠总时间。结果①同一日龄(7日龄)不同性别的果蝇之间白天(12h)及夜间(12h)平均睡眠时间的长短存在着显著差异。雌果蝇白天(12h)平均睡眠时间短于雄果蝇,而夜间(12h)平均睡眠时间长于雄果蝇。雌果蝇白天(12h)平均睡眠时间显著短于夜间平均睡眠时间(P0.05);而雄果蝇白天(12h)平均睡眠时间与夜间(12h)平均睡眠时间基本持平。②同一性别(雌性)不同日龄的果蝇,随着日龄的增加,其白天(12h)平均睡眠时间有逐渐缩短的趋势,27日龄的果蝇睡眠时间减少相对明显,32日龄果蝇的睡眠时间有所恢复,相互之间存在着显著差异(P0.05)。夜间(12h)平均睡眠时间有逐渐延长的趋势,27日龄果蝇的夜间平均睡眠时间有所减少,32日龄果蝇的夜间平均睡眠时间相对有所恢复,相互之间存在着显著差异(P0.05)。结论性别与日龄等生理因素对果蝇24h睡眠时间有显著的影响。     

Novel Fraction Collector for Studying the Oviposition Rhythm in the Turnip Moth

Turnip moths, Agrotis segetum (Schiff.) (Lepidoptera: Noctuidae), were held in a transparent plastic box with a window opening to a rotating paper drum upon which the females could lay eggs. A novel fraction collector, consisting of a standard 24-hr wall timer and simple electronic circuit, served to rotate the paper in hourly increments. The entire apparatus was housed in an environmental chamber on a 16 hr light: 8 hr dark photoperiod at constant 23.7°C and 55% r.h. Under these conditions a circadian rhythm of egg laying was indicated with a mean activity time 0.2 hr before dark and standard deviation of 2.1 hr. The relative egg productions during the second to seventh day of oviposition peaked on the third day. Differences in the circadian rhythms of mating and oviposition are considered in terms of ecological fitness.     

Oviposition and development of Drosophila modified by magnetic fields

Drosophila flies placed in a habitat with two lateral boxes demonstrated sensitivity to magnetic fields: Oviposition decreased by exposure to pulsated extremely low frequency (ELF) (100)Hz, 1.76 miliTesla (mT) and sinusosidal fields (50 Hz, 1 mT), while there was no initial effect of exposure to a static magnetic field (4.5 mT). Drosophila eggs treated for 48 h with the above described fields showed that (1) mortality of eggs was lower in controls than in eggs exposed to all tested magnetic fields; (2) mortality of larvae increased when a permanent magnet was used; (3) mortality of pupae was highest when a permanent magnet was used; and (4) general adult viability was highest in controls (67%) and diminished progressively when eggs were exposed to pulsated (55%), sinusoidal (45%), and static (35%) magnetic fields.     

Oviposition pattern of several Drosophila species under various light environments

The oviposition pattern over two continuous days under constant light (LL) and light-and-dark (LD) conditions was studied by means of a special apparatus; four Drosophila species (D. lutescens, D. melanogaster, D. hydei, and D. virilis) were used. The results showed that: (1) Under the LL condition, the oviposition pattern was characteristic for each species. The number of eggs laid by D. lutescens was smaller than that laid by the other species, and the oviposition pattern of this species was rhythmical. Females of D. melanogaster laid eggs continuously, but at a low rate. In contrast, D. hydei and D. virilis laid eggs in clusters, the total numbers of eggs being larger than those of D. lutescens and D. melanogaster. (2) Females of three species (D. lutescens, D. melanogaster, and D. virilis) laid more eggs in the light phase than in the dark phase under the LD condition. However, no consistent trend was obtained with D. hydei, suggesting that the oviposition pattern of this species is indifferent to the light condition (i.e., it is independent of it). (3) No effects of pre-experimental light condition on the oviposition were found for any of the species. The light-dependency of the oviposition pattern is discussed from the viewpoint of adaptation.     

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. (). 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.     

Oviposition of resistant and susceptible strains of Drosophila melanogaster in the presence of deltamethrin

Oviposition of three strains of Drosophila melanogaster in the presence of deltamethrin was observed. These strains had different levels of physiological susceptibility to deltamethrin. Two-choice tests were conducted with couples of flies in petri-dish arenas containing two oviposition dishes. On the first day of the experiment, females were given a choice between a treated oviposition dish and an untreated control dish. On the second day of the experiment, two control oviposition dishes were given to females. Although individual females showed a tendency to aggregate their eggs in one of the dishes, control experiments demonstrated an overall equal distribution of eggs between the dishes. When one of the two oviposition dishes in the arena was treated with deltamethrin, the percentage of females ovipositing and the mean number of eggs laid by females were reduced, compared with control arenas. Females avoided the treated oviposition dish and laid significantly more eggs on the control dish. Furthermore, when the deltamethrin concentration was increased on the first day, female flies postponed their oviposition and laid significantly more eggs on the second day. The resistant strain, SR, demonstrated the same capacity to select the untreated site for oviposition as the susceptible strain, but it showed a smaller oviposition reduction and egg retention. The relationship between physiological and behavioural susceptibility to deltamethrin is discussed.     

Juvenile Hormone Controls Oviposition and Fertility in Drosophila virilis during Starvation

Degradation of juvenile hormone and reproductive function during starvation and experimental increase of the juvenile hormone titer were studied in wild type and mutant D. virilis females incapable to respond to heat stress by changes in juvenile hormone metabolism and fertility. After 24-hour starvation, the females of both lines were characterized by a decreased level of juvenile hormone degradation, 24-hour delay of oviposition, increased oviposition within 3 h after the termination of starvation, and decreased fertility within three days. Application of exogenous juvenile hormone also led to a decreased level of its degradation and 24-hour arrest of oviposition. Experimental increase of the juvenile hormone titer before the beginning of starvation led to a sharply increase fertility (number of laid eggs and number of progenies) within the first 24 h after the termination of starvation. The dynamics of juvenile hormone degradation and of fertility were similar after starvation and upon application of the exogenous hormone. The role of juvenile hormone in the control of egg maturation and laying under stress conditions has been discussed.     

Effects of Choline Depletion on the Circadian Rhythm in Neurospora crassa

One approach to identifying components of the circadian oscillator is to screen for clock defects in mutants with known biochemical lesions. The chol-1 mutant of Neurospora crassa is defective in the first methylation step of phosphatidylcholine synthesis, the conversion of phosphatidylethanolamine to phosphatidylmonomethylethanolamine, and requires choline for normal growth. Choline depletion of this mutant inhibits growth and lengthens the period of the rhythm of conidiation. On high levels of choline (above 20 µM), the growth rate and the period of the rhythm are normal. Below about 10 µM choline, the growth rate and period length depend on the choline concentration, and the period is about 58 h on minimal medium without choline. Choline depletion decreases period stability, and replicate cultures do not remain in phase due to variability in period within each culture. At intermediate levels of choline (around 10 µM) cultures are often arrhythmic. The choline requirement for growth can be met by the phosphatidylcholine precursors monomethylethanolamine and dimethylethanolamine, and these supplements also restore a normal period. Choline depletion of the chol-1 strain exaggerates the rhythm in growth rate previously reported in a chol + strain. Growth rate during formation of a conidial band (measured as forward advance of the mycelial front) is less than half of the maximum rate during non-conidiating interband formation. Choline-depleted cultures can be entrained to light/dark (LD) cycles with periods near to their free-running periods. Cultures on 10 µM choline (with a free-running period of about 25 h) can be entrained to a 24 h (12:12) LD cycle, but not to a 36 h (18:18) or 48 h (24:24) LD cycle. Cultures on 0.5 µM choline (free-running period of about 52 h) or minimal medium (free-running period of about 58 h) can be entrained to 18:18 and 24:24 LD cycles, but not a 12:12 cycle. The phase relationship of the conidiation rhythm to the zeitgeber for low-choline cultures in LD 24:24 is similar to high choline cultures in LD 12:12. Continuous light abolishes rhythmicity in choline-depleted cultures. These results may indicate a role for membrane phospholipids, and the metabolites of phosphatidylcholine in particular, in the control of the period of the circadian oscillator in Neurospora.     

Effects of Choline Depletion on the Circadian Rhythm in Neurospora crassa

One approach to identifying components of the circadian oscillator is to screen for clock defects in mutants with known biochemical lesions. The chol-1 mutant of Neurospora crassa is defective in the first methylation step of phosphatidylcholine synthesis, the conversion of phosphatidylethanolamine to phosphatidylmonomethylethanolamine, and requires choline for normal growth. Choline depletion of this mutant inhibits growth and lengthens the period of the rhythm of conidiation. On high levels of choline (above 20 µM), the growth rate and the period of the rhythm are normal. Below about 10 µM choline, the growth rate and period length depend on the choline concentration, and the period is about 58 h on minimal medium without choline. Choline depletion decreases period stability, and replicate cultures do not remain in phase due to variability in period within each culture. At intermediate levels of choline (around 10 µM) cultures are often arrhythmic. The choline requirement for growth can be met by the phosphatidylcholine precursors monomethylethanolamine and dimethylethanolamine, and these supplements also restore a normal period. Choline depletion of the chol-1 strain exaggerates the rhythm in growth rate previously reported in a chol + strain. Growth rate during formation of a conidial band (measured as forward advance of the mycelial front) is less than half of the maximum rate during non-conidiating interband formation. Choline-depleted cultures can be entrained to light/dark (LD) cycles with periods near to their free-running periods. Cultures on 10 µM choline (with a free-running period of about 25 h) can be entrained to a 24 h (12:12) LD cycle, but not to a 36 h (18:18) or 48 h (24:24) LD cycle. Cultures on 0.5 µM choline (free-running period of about 52 h) or minimal medium (free-running period of about 58 h) can be entrained to 18:18 and 24:24 LD cycles, but not a 12:12 cycle. The phase relationship of the conidiation rhythm to the zeitgeber for low-choline cultures in LD 24:24 is similar to high choline cultures in LD 12:12. Continuous light abolishes rhythmicity in choline-depleted cultures. These results may indicate a role for membrane phospholipids, and the metabolites of phosphatidylcholine in particular, in the control of the period of the circadian oscillator in Neurospora .     

Circadian Rhythm of Temperature Preference and Its Neural Control in Drosophila

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Highlights? We identify a novel circadian behavior in flies, temperature preference rhythm (TPR) ? Drosophila TPR follows a similar pattern as body temperature rhythm in humans ? Drosophila TPR is regulated independently from circadian locomotor activity ? TPR is controlled by a newly identified DN2-based pacemaker circuit in the brain     

Adult Emergence Rhythm of Fruit Flies Drosophila melanogaster under Seminatural Conditions

In insects, the role of circadian clocks in the temporal regulation of adult emergence rhythm under natural conditions has not previously been reported. Here we present the results of a study aimed at examining the time course and waveform of emergence rhythm in the fruit fly Drosophila melanogaster under seminatural condition (SN). We studied this rhythm in wild-type and clock mutant flies under SN in parallel with laboratory condition (LAB) to examine (1) how the rhythm differs between SN and LAB, (2) what roles the circadian clock protein PERIOD and the circadian photoreceptor CRYPTOCHROME (CRY) play in the regulation of emergence rhythm under SN, and (3) whether there is seasonality in the rhythm. Under SN, wild-type flies displayed tightly gated emergence, peaking at "dawn" and gradually tapering down toward the evening, with little or no emergence by night, while in LAB, flies emerged throughout the light phase of light-dark (LD) cycles. The period loss-of-function mutant (per ( 0 )) flies were arrhythmic in LAB but displayed weak rhythmic emergence under SN. Under SN, cry mutants displayed less robust rhythm with wider gates, greater variance in peak timing, and enhanced nighttime emergence compared to controls. Furthermore, flies showed seasonal variation in emergence rhythm, coupled either to light or to humidity/temperature depending on the severity of environmental conditions. These results suggest that adult emergence rhythm of Drosophila is more robust in nature, is coupled to environmental cycles, and shows seasonal variations.     

Effects of Illumination on the Circadian Motor Rhythm of the Chelipeds of Crayfish

The effects of different illumination conditions on the main parameters of the circadian motor rhythms of the two chelipeds of the crayfish, Procambarus digueti, were compared. Under either constant darkness (DD) or constant light (LL) the phase relationship between the two circadian rhythms was more stable than under entrained conditions (LD cycles). These results suggest that the oscillators responsible for these rhythms differ in their sensitivity to light. The role of paired organs in the internal temporal order of the crayfish is discussed.