Reproductive and developmental consequences of a diapause maternal effect in the flesh fly, Sarcophaga bullata

Abstract Progeny of Sarcophaga bullata produced from mothers with a history of short day will not enter pupal diapause even if they are reared in a strong diapause-inducing environment (LD 12:12 h at 20^oC). Short-day exposure and diapause commitment are normally inseparable, but this maternal effect provides a tool for examining separately the effect of photoperiod and diapause commitment. Duration of the wandering period of the third instar is longer in diapause-destined larvae than in non-diapause-destined larvae, and fecundity of flies that have experienced pupal diapause is lower than in long-day flies that have not been through diapause. The puparia of diapausing pupae contain more hydrocarbons than puparia of nondiapausing pupae, and this contributes to higher rates of net transpiration for the nondiapausing flies. Flies showing the maternal effect (short-day experience but no diapause) show an intermediate response: length of wandering, fecundity rate and quantities of puparial hydrocarbon are between the extremes observed in the other two groups of flies. Thus, the maternal effect switches the developmental programme to nondiapause, but the progeny retain some characteristics of diapause. Evidence from reciprocal crosses indicates that the photoperiodic history of the female, rather than the male, is responsible for the influence on fecundity.     

Diapause of the southwestern corn borer, Diatraea grandiosella: Utilization of fat body and haemolymph reserves

The utilization of metabolic reserves of mature southwestern corn borers held in two regimes (23° 12L:12D and 30° 24L:0D) which permitted different rates of diapause development was studied. Diapause larvae which had been reared on a meridic diet or host-plant tissue were compared. Data were obtained on the fate of lipid, glycogen, protein and amino acid reserves of the fat body and haemolymph during diapause. The major results showed that lipids comprised ca. 80% of the fat body dry weight and formed the principal reserve of diapause larvae. Thin layer chromatographic analyses showed that triglycerides made up >90% of the fat body lipids. Protein, amino acids and glycogen were found to be of secondary importance during diapause since they made up <15% of the fat body dry weight. In contrast, the haemolymph had a high protein and low amino acid, lipid, and glycogen content. Haemolymph proteins supplemented the fat body lipid reserves and were drawn upon during the later stages of diapause.

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Zusammenfassung Die Art und das Schicksal der Stoffwechselreserven des Fettkörpers und der Haemolymphe diapausierender Südwest-Maiszünsler, Diatraea grandiosella, wurden untersucht. Im Labor herangezogene und im Freien gesammelte junge Diapause-Raupen wurden zwei verschiedenen Regimen unterworfen, welche signifikant verschiedene Diapause-Entwicklungsraten gewährleisteten: 23° 12L:12D und 30° 24L:0D. Als Daten wurden festgestellt: Verpuppungsraten, Gesamtkörpergewicht und der Verbrauch der Fett-, Glykogen-, Protein- und Aminosäure-Reserven des Fettkörpers und der Haemolymphe während der Diapause unter beiden Bedingungen. Obwohl die Freilandraupen im allgemeinen größer als die Labortiere waren, wurden doch wenig qualitative Unterschiede zwischen beiden Gruppen gefunden. Als Hauptergebnis zeigte sich, daß die Fette, die 80% des Fettkörper-Trockengewichts ausmachen, die hauptsächliche Stoffwechsel-Reserve darstellen. Sie bestehen überwiegend (>90%) aus Triglyceriden und wurden während der Diapause allmählich verbraucht. Eiweiß, Aminosäuren und Glykogen machen nur weniger als 15% des Fettkörper-Trockengewichts aus. Im Gegensatz dazu wies die Haemolymphe der diapausierenden Raupen einen relativ hohen Eiweiß- und geringen Aminosäure-, Fett- und Glykogen-Gehalt auf. Haemolymphe-Proteine ergänzten die Fettreserven des Fettkörpers und wurden während der späteren Stadien der Diapause abgebaut.

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Contribution from the Missouri Agricultural Experiment Station, Columbia, as journal series no. 6546.     

A maternal effect that eliminates pupal diapause in progeny of the flesh fly, Sarcophaga bullata

Flesh flies that have experienced pupal diapause produce progeny that will not enter diapause even when reared in a strongly diapause-inducing environment. The effect is determined, not by diapause itself, but by the short days previously received by the larvae during the programming of pupal diapause. Reciprocal cross matings indicate that the effect is transmitted solely by the female parent. Though the embryos develop within the uterus of the female, the maternal effect is transmitted prior to the onset of embryogenesis, probably during oögenesis. Only by rearing a generation in long-day (nondiapausing) conditions can the capacity for pupal diapause be restored in the progeny. The effect is likely to provide an adaptive mechanism for preventing an untimely diapause response among the progeny of overwintering females that emerge early in the spring.     

Ontogenetic patterns of cold-hardiness and glycerol production in Sarcophaga crassipalpis

Developmental patterns of low-temperature tolerance and glycerol production were determined for larval, pupal and adult stages of the flesh fly Sarcophaga crassipalpis Macquart (Diptera: Sarcophagidae). Both diapause and non-diapause-destined flies were reared at relatively high temperatures, 20° or 25°C, prior to testing. Cold tolerance was greatest for diapause pupae aged 12–35 days after pupariation. Among non-diapause-destined flies, pupae exhibited a greater level of low temperature tolerance than larvae or adults. Although diapause pupae were more tolerant than non-diapause pupae maximal cold tolerance was not attained in either group until 10 days after pupariation. Non-diapause-destined feeding and wandering larvae had higher glycerol levels than larvae destined for diapause. During the first 6 weeks after pupariation glycerol titres increased steadily in diapause pupae. Rapid loss of glycerol is associated with the termination of pupal diapause.     

A novel trade-off of insect diapause affecting a sequestered chemical defense

Diapause allows insects to temporally avoid conditions that are unfavorable for development and reproduction. However, diapause may incur a cost in the form of reduced metabolic energy reserves, reduced potential fecundity, and missed reproductive opportunities. This study investigated a hitherto ignored consequence of diapause: trade-offs involving sequestered chemical defense. We examined the aristolochic acid defenses of diapausing and non-diapausing pipevine swallowtail butterflies, Battus philenor. Pipevine swallowtail larvae acquire these chemical defenses from their host plants. Butterflies that emerge following pupal diapause have significantly less fat, a female fitness correlate, compared to those that do not diapause. However, butterflies emerging from diapaused pupae are more chemically defended compared to those that have not undergone diapause. Furthermore, non-diapausing butterflies are confronted with older, lower quality host plants on which to oviposit. Thus, a trade-off exists where butterflies may have greater energy reserves at the cost of less chemical defense and sub-optimal food resources for their larvae, or have substantially less energetic reserves with the benefit of greater chemical defense and plentiful larval food resources.     

Summer decline in populations of the yellow dung fly: diapause or quiescence?

Abstract. Yellow dung fly ( Scathophaga stercoraria (L.)) populations on cow pastures in Central Europe usually show a characteristic summer decline in fly numbers. This has been related to their sensitivity to hot temperatures, but where and in what state the flies spend the summer has remained unclear. Field enclosure experiments revealed no evidence for survival over summer in the pupal stage, as adults never emerged in early autumn from eggs laid in late spring. Laboratory and field evidence shows instead that adults acclimatize physiologically by suppressing reproduction in favour of accumulating lipid (but not glycogen) reserves. Apparently they spend the summer in cooler, forested areas close to the pastures. As reproduction is not entirely shut down, it is suggested that this represents quiescence rather than diapause. Presumably this increases the survival of the flies during the hottest time of the season, and appears to be a flexible life-history strategy, particularly for late-born spring generation individuals.     

Deuterium oxide alters pupal diapause response in the flesh fly, Sarcophaga crassipalpis

ABSTRACT. Deuterium oxide averts pupal diapause in the flesh fly Sarcophaga crassipalpis Macquart when fed to larvae or when applied topically to photosensitive embryos exposed to short daylength. Deuterium oxide was not effective in promoting diapause when presented to embryos or larvae reared at long daylength. The effect of deuterium oxide appears to be cumulative in the larval state: increasing exposure time progressively reduces diapause response. If flies reared on deuterium oxide are exposed to continuous darkness, the diapause response remains high, thus implying that the physiological capacity for diapause is not disrupted. We suggest that deuterium oxide exerts its effect on the circadian rhythm controlling diapause induction.     

Stimulatory effect of organic solvents on initiating development in diapausing pupae of the flesh fly, Sarcophaga crassipalpis, and the tobacco hornworm, Manduca sexta

ABSTRACT. Alkanes, diethyl ether, and various other organic solvents proved to be potent stimulants of development in diapausing pupae of Sarcophaga crassipalpis Macquart and of Manduca sexta (Johansson). Topical application of 2μl or vapour exposure for 1–2h was sufficient stimulation for the flies, but the solvent had to be injected to elicit the response in the hornworms. In flies, oxygen consumption increased nearly 100-fold within 15 min of hexane application, and thereafter persisted at non-diapause levels. Sensitivity of fly pupae to hexane remained high throughout diapause but acetone sensitivity dropped sharply after the second day in diapause. Acetone applied the day before the onset of diapause averted diapause in flies, and topical application to hornworm larvae 3 days before pupation likewise prevented pupal diapause. Debrained pupae failed to respond to solvent treatment, and we conclude that it is the brain, rather than the prothoracic gland, that responds directly to stimulation.     

Larval diapause duration and fat metabolism in three geographical strains of the blow fly,Calliphora vicina

Diapausing larvae of the blow fly, Calliphora vicina, from three geographical strains exposed, as adults, to short days, were maintained under identical conditions (darkness, 11-12 degrees C) and examined for changes in wet weight, dry weight, water and fat content during diapause development to the emergence of post-diapause adults. Larvae produced by flies originating from northern Finland (Nallikari, 65 degrees N) showed a longer, more intense, diapause than those from localities further south (Edinburgh, Scotland, 55 degrees N and Barga, Italy, 44 degrees N), but all three strains showed similar rates of loss of the parameters measured. This was also the case for post-diapause adults, flies of the Barga strain with its relatively short diapause emerging with greater residual fat reserves than flies from the Edinburgh or Nallikari strains with their more protracted diapause. It was concluded that the rates of water and fat loss were functions of the conditions used for diapause larval maintenance (probably temperature) rather than the maternally programmed degree of diapause incidence, or of its 'depth' or 'intensity'.     

Metabolic dynamics across prolonged diapause development in larvae of the sawfly,Cephalcia chuxiongica (Hymenoptera: Pamphiliidae)

Nutrient metabolism is crucial for the survival of insects through the diapause. However, little is known about the metabolic mechanism of prolonged diapause. The sawfly, Cephalcia chuxiongica (Hymenoptera: Pamphiliidae), is a notorious defoliator of pine trees in southwest China. One of the distinguishing biological characteristics of this pest is the prolonged diapause of about 1.5 years. In this study, the body lipid, carbohydrate (total body sugar, glycogen, trehalose, and glucose), protein, and glycerol contents were measured in diapausing larvae of C. chuxiongica. The results showed that the changes of biochemical composition in C. chuxiongica are associated with the diapause initiation, maintenance, and termination phases. During the initiation phase, trehalose, glucose, and glycerol increased significantly, but glycogen decreased sharply. In general, the lipid, carbohydrate, and glycerol levels decreased gradually across the maintenance phase. At termination phase, the contents of glycogen and lipid persistently decreased, while an increase of trehalose, glucose, and glycerol contents were detected. The protein level was significantly higher at maintenance phase than at initiation and termination phases. It was also found that elevation of trehalose, glucose, and glycerol contents occurred in winter. These implies that the metabolites with altered levels in diapausing larvae of C. chuxiongica are responsible for maintaining a prolonged development and overwintering.     

Photoperiodic sensitivity and diapause induction during ovarian,embryonic and larval development of the flesh fly,Sarcophaga argyrostoma

Sensitivity to the daily photoperiod, particularly with respect to pupal diapause induction, was studied during ovarian, embryonic, and larval development of the flesh flySarcophaga argyrostoma. Large flies were shown to have a greater number of primary follicles in their ovaries and to be capable of limited ovarian maturation in the absence of exogenous protein (autogeny). Such ovarian development occurred independently of photoperiod. However, long days experienced during embryogenesis caused more rapid development, and earlier larviposition, than short days. Short days during embryonic and subsequent larval development also induced pupal diapause, whereas long days led to continuous or non-diapause development of the pupae. Pupal diapause could not be induced by photoperiods during the vitellogenic phase of ovarian development. InSarcophaga argyrostoma, a maternal effect preventing pupal diapause among the progeny of files with a diapause history was not observed.     

Effect of body size on energy reserves in Culex pipiens pallens females (Diptera: Culicidae)

We examined the relationship between body size and energy reserves of female Culex pipiens pallens under laboratory conditions. Small and large‐sized adult mosquitoes were obtained from larvae reared at different densities. There was a significantly positive relationship between pupal body weight and adult wing length depending on body sizes. Studies showed large females contained significantly higher contents of glycogen and lipid but lower protein stores in comparison to small females. Large sized mosquitoes accumulated higher percentages of glycogen (21.2% vs 15.9%) and lipid (45.8% vs 30.7%) but lower levels of protein (33.0% vs 53.4%) than small females. This result suggests that larval‐derived glycogen and lipid stores may be important in determining the body size of female Cx. pipiens pallens.     

Physiological and biological patterns of a highland and a coastal population of the European cherry fruit fly during diapause

Adult emergence of univoltine temperate insect species and its synchronization with specific host phenological stages is mainly regulated by obligatory pupal diapause. Although a few studies have investigated the factors affecting diapause intensity, little attention has been paid to the physiological alterations and metabolic regulation that take place during diapause. Here, we describe differences in diapause between a highland and a coastal Greek population of the European cherry fruit fly Rhagoletis cerasi, a major pest of sweet and sour cherries in many European countries. Pupae of both populations were exposed to the environmental conditions prevailing in the two areas and diapause termination was observed under laboratory conditions. The regulation of energetic metabolites during the long pupae stage was examined under both field and laboratory conditions. Differences in diapause intensity revealed that the two populations have adapted to the local geographical and climatic conditions and have different requirements for low temperatures to terminate diapause. The coastal population undergoes a shorter diapause and adults emerge more rapidly, especially in the highland area. The highland population failed to terminate diapause (<40% adult emergence) in the coastal area. Both populations draw on their major energetic reserves (lipids and protein) similarly during diapause. Nevertheless, regulation of carbohydrate and glycogen reserves seems to vary between the populations: major peaks of these stored nutrients occur on different dates in the two populations, suggesting a differential regulation. Differences in diapause intensity imply a genetic differentiation between the two populations. The importance of our findings in understanding the physiological patterns during obligatory diapause of a univoltine insect species, as well as the practical implications for the development of specific phenological models for the European cherry fruit fly are discussed.     

大斑芫菁滞育幼虫在滞育不同阶段体内糖类和醇类含量的变化

在以卵滞育的昆虫中昆虫滞育时的生理代谢特点已经得到了大量研究。本文对以末龄幼虫（5龄）滞育的大斑芫菁Mylabris phalerate（Pallas）在不同滞育阶段体内糖类和醇类代谢的特征进行了研究。结果表明： 滞育个体血淋巴中的海藻糖含量高于非滞育个体,且随滞育时间的加大逐渐升高,滞育5个月时达到最大值,为5.61 μmol/mL。糖原的含量随滞育的进程逐渐减少,滞育初期（0.5个月）为0.72 mg/mL,到滞育末期（5个月）时仅为0.1 mg/mL。滞育个体脂肪体中的海藻糖含量都高于非滞育个体,滞育1个月时为非滞育个体的3倍,至滞育末期时达非滞育个体的5倍,为2.5 μmol/g脂肪体。糖原含量总体变化趋势是随滞育时间的加大逐渐减少,滞育早期和中期都高于非滞育个体。在滞育过程中血淋巴积累的小分子多元醇主要为甘油,其次是山梨醇;而在脂肪体中主要为甘油,其次是甘露醇,少量积累山梨醇：表明大斑芫菁滞育幼虫主要积累的是海藻糖和一些小分子多元醇。滞育幼虫在准备滞育时储备了大量糖原,这些糖原可能为滞育期间海藻糖、山梨醇和甘油的代谢提供了原料。     

Water and carbohydrate levels at different developmental stages and dynamics in hibernating pupae of Pieris melete (Lepidoptera: Pieridae)

For insight into the physiological indicators of diapause in Pieris melete, water and carbohydrate (glycogen and trehalose) levels were measured under both natural and laboratory conditions. The highest water content (3.71–3.79 mg/mg dry weight) was found in larvae and developing pupae, which was substantially higher than in diapausing pupae (2.59 mg/mg dry weight). Water content was almost stable during diapause, except for individuals approaching diapause termination (3.43–3.58 mg/mg dry weight). The total carbohydrate level was significantly higher in pre‐pupae (47.41 μg/mg) compared to larvae (22.80 μg/mg) and developing pupae (21.48 μg/mg). The highest level of trehalose was detected in winter diapausing pupae, and no trehalose was found in larvae or developing pupae. Levels of glycogen were highest in pre‐pupae and lowest in diapausing pupae. Levels of total carbohydrate decreased as diapause proceeded, and no significant changes were found in trehalose levels for diapausing pupae under natural conditions or treated for 60–90 days at 5°C. Pupae treated at 20°C for 60–90 days had significantly lower levels of trehalose than those treated for 30 days. Glycogen content was relatively stable at 5°C, but increased after treatment under natural conditions and 20°C for more than 60 days. These results suggest that the dynamics of water and carbohydrate levels are potential physiological diapause indicators, which show metabolic differences between trehalose and glycogen during diapause development.     

Diapause development and acclimation regulating enzymes associated with glycerol synthesis in the Shonai ecotype of the rice stem borer larva,Chilo suppressalis walker

Overwintering larvae of the Shonai ecotype of the rice stem borer, Chilo suppressalis, enter diapause in early September and terminate diapause at the end of October. Cold acclimation at 0°C did not influence glycerol, trehalose or glycogen content in larvae collected on 22 September. Acclimation at 0°C increased the glycerol content and reduced the glycogen content significantly in larvae collected on 2 October and 22 November compared with acclimation at 15°C. These results indicate that overwintering larvae at different phases of diapause development respond differently to the low temperature stimulus for glycerol synthesis. Thus, we evaluated the metabolic rearrangements associated with glycerol synthesis during diapause development and after temperature acclimation. Larvae collected on 2 October were acclimated at 15°C for 15 and 60 days. Some of those acclimated at 15°C were then moved to 0°C for 15 days. The larvae acclimated at 15°C for 15 days were in deep diapause and accumulated little glycerol, while larvae acclimated at 15°C for 60 days were nearly ready to emerge from diapause and accumulated glycerol at 155.5 μmol/g. When larvae acclimated to 15°C for 15 days were transferred to 0°C, glycerol accumulation was stimulated to the same extent (ca 140 μmol/g) as it was in larvae that were acclimated to 15°C for 60 days and then transferred to 0°C. These results indicate that low temperature has a cumulative effect on glycerol production in larvae at different phases of diapause development. Glycerol accumulation was accomplished by activation of glycogen phosphorylase and inhibition of fructose-1,6-bisphosphatase, and activation of enzymes associated with glycerol synthesis, mainly glyceraldehyde-3-phosphatase and polyol dehydrogenase with glyceraldehyde activity.     

Nutrient reserves in starving black carpet beetle larvae infected with the eugregarine Pyxinia frenzeli

Starvation-mediated alterations of nutrient reserves (lipid, protein, glycogen) of larvae of the black carpet beetle, Attagenus megatoma (=Attagenus piceus), were studied. Quantitative comparisons of these materials between uninfected larvae and those infected with the eugregarine Pyxinia frenzeli were performed in an effort to characterize pathologic conditions elicited by the gregarine. Fresh weight losses were similar in both types of insects; however, infected larvae had a consistently higher moisture content. No differences were detected in the rate of utilization of stored protein, glycogen, or lipid. These data provide evidence that P. frenzeli is a commensal or mutualist, rather than a pathogen.     

Reduction in the critical number of short days for pupal diapause in Papilio machaon with precocious metamorphosis

Normal and allatectomized larvae of Papilio machaon were transferred from short (light:dark 10:14) to long (light:dark 16:8), or long to short days, on successive days of larval development to examine the critical number of short days necessary for diapause induction. The reciprocal transfer revealed that the normal larvae required 12 consecutive short days during the early instars to raise the incidence of pupal diapause to 50%. The critical number of short days was reduced to 9.5 days when the length of the larval period was cut due to precocious pupation induced by allatectomy. The reduction in the critical number of short days with precocious metamorphosis was less remarkable when the larvae were exposed to short days during the late instars. A possible summation mechanism of photoperiodic information for diapause induction in P. machaon is presented to explain the results obtained.