Photoperiodic Induction Of Diapause Research Articles

Timeless is a critical gene in the diapause of silkworm, Bombyx mori

The diapause is a specific physiological phenomenon induced by circadian zeitgebers of temperature and photoperiod at the stage of maternal embryonic development. In this research, the authors investigated the linkage of diapause and the regulation of circadian rhythm by inspecting the expression profiles of a circadian clock gene timeless (tim) under diapause-inducing temperature and photoperiod inBombyx mori. The results show that the level of tim mRNA was higher in 25LL than in 20LD or in 15DD during the late embryonic stages (EAT 2520-3240°C·h), which is the most effective inducing period of temperature and photoperiod on diapause in the progeny. The tim transcription level was significantly higher in darkness than in light during postembryonic development, which contradicted the results found in the pupa and adult stages at 25°C. Exposure of maternal embryos to a high temperature (25°C) resulted in up-regulated levels of tim mRNA in egg stage of progeny. However, this up-regulation only occurred before egg-age at 72 h, which was a pivot for diapause and diapause termination. In conclusion, diapause-inducing temperature and photoperiod of incubation directly affect tim gene expression throughout the life cycle of B. mori. Key words: Circadian clock gene, timless gene, diapause, temperature, photoperiod, Bombyx mori.

Effects of constant and changing temperature conditions on diapause induction inHelicoverpa armigera(Lepidoptera: Noctuidae)

The effects of photoperiod and temperature on the induction and termination of facultative pupal diapause in Helicoverpa armigera (Lepidoptera: Noctuidae) were investigated under laboratory conditions. Exposing H. armigera larvae to both constant and fluctuating temperature regimes with a mean of 25°C and 20°C resulted in a type-III photoperiodic response curve of a short-long day insect. The long-day critical daylengths for diapause induction were ten hours and 12 hours at the constant temperatures of 25°C and 20°C, respectively. Higher incidences of diapause and higher values both for the longer and the shorter critical photoperiods for diapause induction were observed at fluctuating regimes compared with the corresponding constant ones. At alternating temperatures, the incidence of diapause ranged from 4.2% to 33.3% and was determined by the temperature amplitude of the thermoperiod and by the interaction of cryophase or thermophase with the photoperiod. Helicoverpa armigera larvae seem to respond to photoperiodic stimuli at temperatures >15°C and <30°C; all insects entered diapause at a constant temperature of 15°C, whereas none did so at a constant temperature of 30°C under all the photoperiodic regimes examined. Although chilling was not a prerequisite for diapause termination, exposure of diapausing pupae to chilling conditions significantly accelerated diapause development and the time of adult emergence. Therefore, temperature may be the primary factor controlling the termination of diapause in H. armigera.

The effect of diapause on neutral lipids in the pitcher-plant mosquitoWyeomyia smithiias determined by HPTLC-densitometry

Diapause in insects typically results in metabolic adjustments that may include the levels of feeding and activity, metabolic rate, and the accumulation and utilization of reserves. The objective of this study was to characterize and quantify the various neutral lipid classes in the pitcher-plant mosquito (Wyeomyia smithii) that are associated with photoperiod-induced diapause. We used high-performance thin-layer chromatography (HPTLC) with 10 cm × 20 cm silica gel plates, petroleum ether-diethyl ether-glacial acetic acid 80:20:1 as the mobile phase, and 5% ethanolic phosphomolybdic acid solution as detection reagent to determine the percentage of replicate larvae samples (consisting of 16–31 larvae) that contained free sterols (FS), free fatty acids (FFA), triacylglycerols (TG), methyl esters (ME), and steryl esters (SE). Irrespective of the growth treatment (shortdays or long-days), the greatest concentrations of neutral lipids in all samples examined were TG. The effects of day length were such that du...

Sexual difference in the photoperiodic induction of pupal diapause in the flesh fly Sarcophaga similis

The flesh fly Sarcophaga similis enters pupal diapause in response to short days, but averts diapause under long days. This species shows a sexual difference in the photoperiodic induction of diapause, with females having shorter critical daylength than males. Here, we proposed two hypotheses to explain this sexual difference. First, we proposed a sexual difference in the qualitative evaluation of photoperiods. This hypothesis assumes under the external coincidence model that although the photoinducible phase of both sexes locates at late scotophase, in males, it locates at a slightly earlier phase. However, the results of night interruption experiments clearly ruled out this hypothesis. Because we verified that S. similis evaluated photoperiods quantitatively, we next proposed a sexual difference in the quantitative evaluation of photoperiods. This hypothesis incorporates concepts of a hypothetical substance accumulation that shows a diapause-inducing effect and an internal threshold that serves as a reference to determine the diapause/nondiapause developmental program. In long-day exposure experiments and night interruption experiments, females consistently showed a lower incidence of diapause than males. Thus, the present study data satisfactorily meet the second hypothesis, that is a sexual difference in the quantitative evaluation of photoperiods exists in S. similis.

Photoperiodic diapause under the control of circadian clock genes in an insect

BackgroundMost organisms have evolved a circadian clock in order to anticipate daily environmental changes and many of these organisms are also capable of sophisticated measurement of daylength (photoperiodism) that is used to regulate seasonal events such as diapause, migration and polymorphism. It has been generally accepted that the same elements are involved in both circadian (daily) and seasonal (annual) rhythms because both rely upon daily light-dark cycles. However, as reasonable as this sounds, there remains no conclusive evidence of such a molecular machinery in insects. We have approached this issue by using RNA interference (RNAi) in Riptortus pedestris.ResultsThe cuticle deposition rhythm exhibited the major properties of circadian rhythms, indicating that the rhythm is regulated by a circadian clock. RNAi directed against the circadian clock genes of period and cycle, which are negative and positive regulators in the circadian clock, respectively, disrupted the cuticle deposition rhythm and distinct cuticle layers were produced by these RNAi. Simultaneously, period RNAi caused the insect to avert diapause under a diapause-inducing photoperiod whereas cycle RNAi induced diapause under a diapause-averting photoperiod. The expression patterns of juvenile hormone-regulated genes and the application of juvenile hormone analogue suggested that neither ovarian development itself nor a downstream cascade of juvenile hormone secretion, were disturbed by period and cycle RNAi.ConclusionsThis study revealed that the circadian clock genes are crucial not only for daily rhythms but also for photoperiodic diapause. RNAi directed against period and cycle had opposite effects not only in the circadian cuticle deposition rhythm but also in the photoperiodic diapause. These RNAi also had opposite effects on juvenile hormone-regulated gene expression. It is still possible that the circadian clock genes pleiotropically affect ovarian development but, based on these results, we suggest that the circadian clock operated by the circadian clock genes, period and cycle, governs seasonal timing as well as the daily rhythms.See Commentary: http://www.biomedcentral.com/1741-7007/8/115

Possible involvement of distinct photoreceptors in the photoperiodic induction of diapause in the flesh fly Sarcophaga similis

Physiological characteristics of the photoreceptors involved in the photoperiodic induction of diapause were investigated in the flesh fly Sarcophaga similis. Both the early and late phases of scotophase were sensitive to light and a light pulse during each of these phases prevented diapause. Certain physiological differences between the phases were, nevertheless, detected. Compared with early scotophase, late scotophase required a light pulse with a long period and a large number of night interruption photoperiodic cycles in order to effectively prevent diapause. The diapause-averting effects of a light pulse during early scotophase were canceled by an additional long dark period, but those during late scotophase were not. Thus, the diapause-averting effects produced during early scotophase are different to those produced during late scotophase. The early scotophase was sensitive to light at wavelengths of 470 nm or shorter, but not to light of 583 nm or longer. In contrast, the late scotophase was sensitive to light of a broad range of wavelengths, ranging from 395 to 660 nm. Furthermore, the early scotophase was considerably more sensitive to monochromatic light with low photon flux density than the late scotophase. These results suggest that different types of photoreceptor are involved in the photoperiodic response.

Genetics of the photoperiodic larval diapause in Chymomyza costata (Diptera; Drosophilidae)

The genetic control of the photoperiodic larval diapause of Chymomyza costata was studied by hybridization, backcross and selection tests. The strains used in the experiment, normal photoperiodic-diapause strains from Finland (VK) and Japan (SP) and a mutant non-photoperiodic-diapause strain (NP), which was selected from the Japanese population, differed from each other with respect to critical daylength and critical temperature measured at long-day or short-day conditions. The loss of photoperiodic response in NP was shown to be associated with the lowering of the short-day critical temperature to the level of the long-day critical temperature. A recessive allele at a single autosomal locus is responsible for the trait. The differences between VK and SP, or VK and NP, in the critical daylength are due to at least two loci, one on the X chromosome and one on an autosome. The critical daylengths of F1 females obtained from reciprocal crosses between SP and VK were intermediate between those of the parental strains. SP and VK responded quantitatively to photoperiod in diapause induction; a shorter photoperiod was more effective in inducing diapause than a longer photoperiod.

Effects of light quality and intensity on diapause induction in the two-spotted spider mite, Tetranychus urticae

It has been known that diapause is not induced in populations of the two-spotted spider mite, Tetranychus urticae, under continuous darkness (DD). When the light intensity was changed under LD 8:16 at 18°C, the threshold intensity for blue light (475 nm) to induce 50% of diapause was below 50 mW/m2; and the blue light was most effective in photoperiodic induction of diapause. The threshold intensities for green (572 nm) and orange (612 nm) light were 50–500 and 500–2,500 mW/m2, respectively. T. urticae showed no sensitivity to red light (658 nm) even at 2,500 mW/m2 intensity. Low diapause incidence under long wavelengths was probably due to the absence of photoreception by photoreceptor pigments for photoperiodic time measurement, or for circadian entrainment required for photoperiodic induction.

10 ナミニクバエの休眠誘導日長と低温耐性からセンチニクバエとの分布域の比較(第59回日本衛生動物学会東日本支部大会講演要旨)

10 ナミニクバエの休眠誘導日長と低温耐性からセンチニクバエとの分布域の比較(第59回日本衛生動物学会東日本支部大会講演要旨)

The role of temperature and photoperiod in diapause induction in the brassica leaf beetle, Phaedon brassicae (Coleoptera: Chrysomelidae)

The brassica leaf beetle, Phaedon brassicae Baly (Coleoptera: Chrysomelidae), one of the pests infesting cruciferous vegetables in China and Japan, is a multivoltine species that oversummers and overwinters as an adult. The effects of both temperature and photoperiod on reproductive diapause induction were systematically investigated in this beetle. Under 16L : 8D, most of the beetles entered reproductive diapause at 12-30°C, indicating that photoperiod played a crucial role in estivation diapause induction. Under 12L : 12D, all adults developed without diapause at 28 and 30°C; less than 25% of the individuals entered reproductive diapause at 16-24°C; however, 46.1% of the individuals entered diapause at 12°C, suggesting that low temperature also had a relatively important influence on the determination of diapause. The photoperiodic response curves indicate that this species is a typical short-day species. The critical day-lengths at 20, 24 and 28°C were 13.2, 13.6 and 13.8 h, respectively. Transferring them from 16L : 8D to 12L : 12D or vice versa at different ages and/or stages during their development revealed that the photoperiod experienced by adults during the first 11 days might be important for diapause determination, even though an effect of photoperiod on the larval and pupal stages can not be excluded. Transferring individuals kept at a photoperiod of 12L : 12D from 25°C to 12°C or vice versa at different ages and/or stages during their development revealed that the temperature cue for diapause is mainly perceived by the late instar larvae and pupae.

Effects of extending the light phase on diapause induction in a Japanese population of the two-spotted spider mite, Tetranychus urticae

Artificial lighting is a merit of a 'plant factory', which might be utilized to suppress an increase in pest population. We investigated the effects of extending the light phase on diapause induction in the two-spotted spider mite (TSSM), Tetranychus urticae. TSSM were reared at 18 degrees C under light phases ranging from 2 to 64 h combined with a constant dark phase of 16 h in aluminum bottles, with white light emitting diodes attached inside to minimize fluctuations in air temperature between the light and dark phases. Diapause was induced in adult TSSM females when the light phase was 24 h or shorter, and diapause induction was inhibited when the light phase extended over 32 h. The development of deutonymphs was delayed under a diapause-inducing photoperiod. Diapause inducing photoperiods may suppress an increase in the TSSM population, by slowing down development and reproduction.

Diapause in the Leaf Beetle &lt;I&gt;Diorhabda elongata&lt;/I&gt; (Coleoptera: Chrysomelidae), a Biological Control Agent for Tamarisk (&lt;I&gt;Tamarix&lt;/I&gt; spp.)

The tamarisk leaf beetle, Diorhabda elongata Brullé deserticola Chen, was collected in northwestern China and has been released in the western United States to control tamarisk (Tamarix spp.). Characteristics of diapause and reproductive development in D. elongata were examined to improve management as a biocontrol agent. Under long days, 16:8 (L:D) h, males began to emit aggregation pheromone within 2-3 d of adult emergence, mating occurred, and females oviposited within 7 d of adult emergence. Under short days, 12:12 (L:D) h, males did not emit pheromone, mating did not occur, and both males and females entered reproductive diapause marked by inconspicuous gonads and hypertrophied fat body. Ovaries of diapausing females lacked vitellogenic oocytes, and the ovarioles were clear and narrow, whereas reproductive females had enlarged ovaries with two to three yellow oocytes per ovariole. Diapausing males had thin, transparent accessory glands and ejaculatory ducts, whereas reproductive males had thick white accessory glands and white opaque ejaculatory ducts. Sensitivity to diapause-inducing photoperiods extended into the adult stage. Reproductive females ceased oviposition, resorbed oocytes, and entered diapause when switched from long to short days. Diapause-destined insects ceased feeding and entered the leaf litter 10-20 d after adult emergence, whereas reproductive insects remained on the plants and fed for at least 30 d. Reproductive insects exhibited dispersal behaviors, such as attempted flights, whereas diapause-destined insects did not show dispersal behaviors. Information gained from these studies will be used to better manage populations in the field and to improve rearing and storage in the laboratory.

Photoperiodic Induction of Reproductive Diapause in the Predator Geocoris uliginosus (Hemiptera: Geocoridae)

Abstract The critical photoperiod for diapause induction in the predator Geocoris uliginosus (Say) and the stage/instar(s) sensitive to diapause-inducing photoperiods were determined in the laboratory. Six photoperiods were used for the critical photoperiod experiment (all at 24 ± 1°C): 10:14, 11:13, 12:12, 13:11, 14:10, and 15:9 (L:D) h. The critical photoperiod was ≈13.2 h of light d−1. At 12:12 and 11:13 h, 86–88% of the population entered diapause, whereas 20% or less entered diapause at longer daylength. To determine the stage/instar(s) sensitive to diapause-inducing photoperiods, cohorts of bugs were reciprocally switched between two photoperiods, 15:9 (not diapause-inducing) and 11:13 h (diapause-inducing), at the beginning of the second, third, fourth, and fifth instar, and at the beginning of the adult stage. A given cohort was switched only once during the experiment. Two additional cohorts were reared as controls under the respective photoperiods with no switching throughout the experiment. Exp...

Photoperiod-sensitive developmental delay in facet mutants of the drosophilid fly, Chymomyza costata and the genetic interaction with timeless

Previously, we demonstrated that the biological clock gene , timeless ( tim), is potentially involved in photoperiodic diapause induction in the larvae of the drosophilid fly Chymomyza costata. Suppression of tim transcription was inevitably associated with the loss of diapause induction even under diapause-promoting short-day conditions. In the present paper, I report a novel gene, facet ( fa), which may genetically interact with tim in photoperiodically controlled larval development in this species. I demonstrated the effect of photoperiod on the development of fa morphological mutants. Developmental delay was remarkable in fa larvae under a diapause-preventing photoperiod, 16 h light: 8 h dark/day, in which the wild-type individuals showed normal and synchronous development. The delay was recovered by extension of the light phase of daily light/dark cycles or the introgression of a deficient tim allele.

PHOTOPERIODIC CONTROL OF ADULT DIAPAUSE IN CHRYSOPERLA SINICA (TJEDER) (NEUROPTERA: CHRYSOPIDAE— I. CRITICAL PHOTOPERIOD AND SENSITIVE STAGES OF ADULT DIAPAUSE INDUCTION

Abstract Photoperiodic sensitivity for diapause induction of the green lacewing, Chrysoperla sinica (Tjeder) was examined at 22°C. The adult diapause of C. sinica was induced by short‐day photoperiods, and the critical photoperiod for its induction was between 12.5L‐11.5D and 13L‐11D.Adults developed without diapause under long‐day conditions, and entered diapause under short‐day conditions. The adult stage was the uppermost sensitive stage for adult diapause induction, adults could go into diapause only when the emerging adults were under diapause‐inducing short‐day photoperiods. The short‐day photoperiodic experience by transferring between 15L: 9D and 9L: 15D at preimaginal stages did not result in adult diapause under 15L: 9D photo regime, although some treatments extended the pre‐oviposition period in adult stage. The results showed that the 3rd instar larvae and pre‐pupae were more sensitive to the photoperiodic change from 15L: 9D to 9L: 15D photo regime than the other preimaginal stages.

Photoperiodic induction of diapause: opening the black box

Abstract. Over several decades, formal experiments measuring diapause responses to variable light inputs have indicated that photoperiodic time measurement in insects is accomplished either by a nonoscillatory ‘hourglass‐like’ mechanism or by oscillatory components of the circadian system. Although both are possible given the present state of our knowledge, a substantial body of evidence strongly suggests that night‐length measurement is a function of the circadian system, and that ‘hourglass‐like’ clocks are manifestations of damping circadian components. The two types of time measurement, ‘hourglass’ and circadian, are therefore parts of a spectrum of mechanisms differing in their damping coefficients. If this view is correct, it may follow that genes and proteins involved in circadian timing are also involved in photoperiodism, although additional genes, or known ‘clock’ genes used in novel ways, may also play a part. This review outlines the experimental evidence for the oscillator clock theory of photoperiodism and suggests ways in which further progress may be made.

Role of Reproductive Diapause in the Adaption of the Tarnished Plant Bug (Heteroptera: Miridae) to Its Winter Habitat in the Mississippi River Delta

Reproductive diapause in the tarnished plant bug, Lygus lineolaris (Palisot de Beau- vois), was studied by dissection of Þeld collected adults or adults reared from Þeld collected nymphs in 1999 Ð2001 in Washington County near Stoneville, MS. The critical photoperiod for diapause induction was 12.5:11.5 (L:D) h, or 12 September. This photoperiod was also near the day-length at which new generation adults produced in late winter and early spring became reproductive. Overwintering adults collected from winter host plants in December 1999 and 2001 began breaking diapause in the second and third weeks of December at a day-length near 10:14 (L:D) h. Most of the overwintering females collected on winter host plants had mature eggs by the end of December in both winters, and new generation adults were produced on winter hosts by the second or third week in March. Overwintering adults also were collected in January 2002 from plant debris not associated with any winter host plant. Most of the females overwintering in plant debris had mature eggs at the end of January, approximately 1 month later than overwintering females collected from winter hosts. This indicated than the adults from plant debris were in a different state of diapause, because they did not overwinter on a food source and matured reproductively at a later date. The winters of 1998 Ð1999 and 1999 Ð2000 were mild, whereas in the winter of 2000 Ð2001, winter host plants were killed or stunted by cold weather. Diapause in plant debris in the winter of 2000 Ð2001 was probably favored, because these adults would be more likely to survive until suitable host plants were available.

Circadian component influences the photoperiodic induction of diapause in a drosophilid fly, Chymomyza costata

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.

Photoperiodic control of the intensity of diapause and diapause development in the bean bug, Riptortus clavatus (Heteroptera: Alydidae)

Adult diapause in Riptortus clavatus (Thunberg) was induced by short-day photoperiods, and the critical daylength for its induction was 13.5 h. When insects were reared from eggs under diapause-inducing photoperiods near the critical daylength, the duration of diapause was shorter than when reared under the shorter daylengths. Adults terminated diapause under long-day photoperiods earlier when they had been raised under a near-critical photoperiod than under shorter daylengths; this indicated that the initial intensity of diapause was dependent on the length of the inducing photoperiod. Not only the photoperiods experienced during preimaginal development but also the value of the long-day photoperiods experienced after adult emergence affected the time of onset of oviposition. When the photophase was shortened, either abruptly or gradually after adult emergence, the duration of diapause was prolonged. Diapause was long when induced by shorter daylengths than the near-critical photoperiod. Different photoperiods have thus different quantitative effects on both the initial intensity of diapause and the rate of diapause development.

Dopamine and serotonin in the larval CNS of a drosophilid fly, Chymomyza costata: are they involved in the regulation of diapause?

Developmental profiles of dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) in the larval CNS of Chymomyza costata were measured by HPLC using electrochemical detection. Larvae of two strains, wild-type (W) and nondiapause mutant (M), were maintained either under long-day (LD, inducing pupariation) or short-day (SD, inducing diapause in W-strain) photoperiods. The levels of DA ranged from 10 fmol/CNS (early 3rd instar larvae) to 60 fmol/CNS (150-day-old diapausing larvae); the range for 5-HT was from 10 fmol/CNS to 75 fmol/CNS in the same larvae. During the 3rd larval instar, which is the decisive stage for photoperiodic induction of diapause, no differences were found in DA developmental profiles between different strains or conditions. Some differences were found in 5-HT developmental profiles, but only after the end of sensitive stage, and were therefore regarded as insignificant for regulation of developmental mode. Similarly, no clear correlations between the developmental profiles of DA and 5-HT and the course of developmental changes during the maintenance and termination of a few-month-long larval diapause were observed. Furthermore, the DA and 5-HT levels in the CNS were pharmacologically manipulated by feeding the larvae with either precursors or enzyme inhibitors of DA and 5-HT biosynthesis. Although retardations of growth and development were observed, the treated larvae retained full capacity for the photoperiodic response, irrespective of the level of DA or 5-HT in their CNS. Larvae with their 5-HT depleted to trace levels survived and were capable of diapause induction, maintenance, and termination. Depletion of DA to trace levels resulted in 100% mortality. Collectively, the present study indicates that 5-HT in the CNS is dispensable for the photoperiodic response in C. costata. More information is needed to elucidate the potential role of DA.