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.     

FIELD STUDIES ON THE INFLUENCE OF WEATHER ON EGG-LAYING BY THE CABBAGE ROOT FLY, ERIOISCHIA BRASSICAE BCHÉ. II

Observations on the intensity and duration of egg-laying by Erioischia brassicae Bché were continued in 1953 on the same site as in 1952. Eggs were first observed on 31 April and the spring peak period of egg-laying lasted from 3 to 30 May with a daily average of 40 eggs/plant. The mean total in spring 1953 was 1287 eggs/plant. Summer peaks occurred on 1–20 July (average 17 eggs/day/plant) and 5–11 August (average 21 eggs/day/plant).
In the field the threshold of reproduction was approximately 60° F. The rate of egg-laying was highest at 65–70° F. and it declined during prolonged periods of higher temperatures.
The annual cycle of generations, as shown by egg counts and confirmed by the examination of puparia, consisted of two generations and a partial third. The spring generation developed without a prolonged diapause, and there was complete emergence during the summer. The overwintering puparia came from the second and third generations of larvae.     

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。     

Influence of ecdysterone, precocene and compounds with juvenile hormone activity on induction, termination and maintenance of diapause in the parasitoid wasp, Nasonia vitripennis

ABSTRACT. Using the Galleria bioassay, no difference could be found between the JH titre of diapausing and developing Nasonia larvae. Compared to the values found in some Lepidoptera, the JH titres in Nasonia larvae are low, c. 14 Galleria units/g live weight. Induction of diapause could not be brought about by topical application of JH I, JH analogues, precocene, or ecdysterone to the maternal generation, nor by treating eggs or larvae with compounds with JH activity. Diapause was easily terminated by topical application of ecdysterone, however. If ecdysterone treatment was preceded by JH-treatment, the percentage of larvae terminating diapause was reduced: JH II seems to be more potent than JH I or JH III in this effect if the interval between JH and ecdysterone treatment is 72 h.     

Characteristics of larvae of the southwestern corn borer, Diatraea grandiosella, obtained from populations present in tropical and temperate regions

A comparative study was undertaken of southwestern corn borers (Diatraea grandiosella) collected from south central Mexico (19°N latitude) and southeast Missouri (37°N latitude). All the life stages of the Mexican insects were found to be larger or heavier, or both, than were those of the Missouri insects. Mexican larvae grew at a higher rate and attained a significantly heavier body weight than did Missouri larvae. Although both Mexican and Missouri larvae underwent ecdyses during diapause, Mexican larvae ecdysed more frequently than did the Missouri larvae at 23°C light:dark 12 h:12 h. Larvae that ecdysed most frequently did not necessarily spend longer in diapause. Electrophoresis of the fat body and haemolymph proteins of Mexican and Missouri larvae revealed similar patterns. The fat body of diapausing Mexican larvae contained substantial amounts of a diapause-associated protein which has been characterized previously from the fat body of Missouri Larvae. Double immunodiffusion confirmed that the diapause-associated protein of the Mexican larvae was identical to that present in the Missouri larvae. Smaller amounts of this protein appear to be present in the fat body of diapausing Mexican larvae than are present in that of diapausing Missouri larvae.     

Relationships between body weight of overwintering larvae and supercooling capacity; diapause intensity and post-diapause reproductive potential in Chilo suppressalis Walker

The rice stem borer, Chilo suppressalis Walker, overwinters in China as a larva in facultative diapause. The instars and body weights of overwintering larvae vary widely. In this paper, the relationships between body weight and supercooling capacity, diapause intensity and post-diapause reproductive potential of overwintering larvae collected in late-stage rice field were examined. There was a significant positive correlation between body weight, instar, and head capsule width, thus the overwintering larvae were divided into five groups based on body weight (I, up to 35.0 mg; II, 35.1-57.0 mg; III, 57.1-79.0 mg; IV, 79.1-101.0 mg; and V, over 101.1 mg) for further analysis. The body water content of the lighter group (I) was significantly higher than that of the heavier groups (IV-V). However, the mean supercooling point decreased with an increase of the mean larval body weight in five groups; mean supercooling point of group I was significantly lower than that of group V, except in January 2009. After transfer of overwintering larvae to 15, 20 and 25 °C on different dates, smaller individuals pupated slightly faster than larger ones at the same temperature, suggesting that diapause was less intense in smaller overwintering larvae. On 19 March 2009 there was a strong positive correlation between larval body weight and the weight of 3 day-old pupae, and the number of eggs carried by 2 day-old adult females at 15, 20 and 25 °C. The average number of eggs carried by 2 day-old adult females differed significantly among different groups. The average number of eggs carried by 2 day-old adult females in group V was significantly greater than those of other groups, and that of group I was significantly lower than those of other groups, suggesting that post-diapause reproductive potential was determined, to a certain extent, by body weight of the overwintering larvae.     

宽翅曲背蝗卵的过冷却能力与抗寒性

采用热电偶法,在室内测定了宽翅曲背蝗卵的过冷却能力及抗寒性.结果表明： 土壤含水量对滞育前卵的含水量有显著影响, 而对卵过冷却点(SCP)的影响不显著,卵含水量随着土壤含水量的升高而上升.不同发育时期卵的SCP、含水量和脂肪含量存在显著差异.随着卵的发育,其含水量从产卵当天的51.5%下降至120 d的46.8%,脂肪含量从10.5%(鲜质量)/19.0%(干质量)上升到14.5%(鲜质量)/28.9%(干质量),而SCP从-23.5 ℃下降至-30.0 ℃;卵SCP与其含水量及脂肪含量存在显著相关关系;深度滞育卵的SCP显著低于滞育前和滞育初期卵的SCP.不同低温强度和处理时间对滞育卵的存活率有显著影响.滞育卵暴露12 h的致死温度为-27.3 ℃,在-25 ℃低温处理的致死时间为22.73 d.滞育卵的SCP与致死温度相近,说明宽翅曲背蝗卵为不耐结冰类型,且SCP是衡量其抗寒性的可靠指标.     

The effect of larval temperature and photoperiod on the incidence of larval diapause in the blowfly, Calliphora vicina

ABSTRACT. The blowfly, Calliphora vicina Meigen (Diptera: Calliphoridae), displays a maternally induced larval diapause. Progeny of adults exposed to short days enter diapause if the larval temperature is 15C or below; exposing adults to long days, or larvae to temperatures above 15C, results in non-diapause. By keeping progeny from short-day parents at the parental temperature of 23.5C for various lengths of time before transfer to 11C, it could be shown that the diapause-averting effect of high temperature operates in the late wandering stage of larva, possibly at the moment of the decision for the brain-ring gland complex to release PTTH/ecdysone at the diapause/non-diapause stage.
Although photoperiodic induction in the blowfly is maternal, previous work had shown that the larvae were also slightly sensitive to photoperiod. From the present study it is evident that also the eggs are photo-sensitive.     

In vitro release of lipophorin from the fat body of nondiapause and diapause larvae of the Southwestern corn borer,Diatraea grandiosella

The release of lipophorin and total protein was examined from the fat body of nondiapause and diapause larvae of the southwestern corn borer, Diatraea grandiosella, incubated in vitro in Grace's medium. The characteristics of the released lipophorin were compared to those of the high-density lipophorin present in the hemolymph of nondiapause and diapause larvae. Over a 4 h incubation period, the fat body of nondiapause larvae released about 1.5 times more total protein and 2 times more lipophorin per mg dry weight than did that of diapause larvae. Lipophorin isolated from the medium in which fat bodies of nondiapause and diapause larvae had been incubated and from the plasma of nondiapause and diapause larvae had similar mean densities of 1.115, 1.112, 1.117 and 1.119 g/ml, respectively. Although the lipid classes detected in lipophorin isolated from the fat body incubation medium and hemolymph were identical, more polar lipids and less diacylglycerol were associated with lipophorin isolated from fat body incubation medium then were associated with lipophorin isolated from the hemolymph. Sterols accounted for about 11% of the total lipids of lipophorin isolated from the fat body incubation medium, whereas they accounted for about 20% of the total lipids of lipophorin from hemolymph. We conclude that the fat body of feeding nondiapause larvae and nonfeeding diapause larvae releases high-density lipophorin.     

Reversal of embryonic diapause in the Australian plague locust, Chortoicetes terminifera (Walker), by temperatures above the development threshold

Diapause was induced in embryos of Chortoicetes terminifera (Walker) by transferring adults from an L:D 15:9 regime to an L:D 12.5:11.5 regime. When incubated at 20°C all eggs in all pods entered and remained in diapause but when incubated at 26, 32 and 38°C a proportion of eggs in some pods did not. Pods incubated at 32°C for up to 6 days, when diapause intervenes and then transferred to 20°C gave the same result as pods incubated at 20°C throughout development. All eggs entered and remained in diapause. If the period at 32°C was extended to 8 days, the proportion remaining in diapause was not significantly different from that found when pods were incubated at 32°C throughout development. In eggs which broke diapause at 32°C there was a pause or slowing down of development for about 2 or 3 days around the stage at which diapause intervenes.     

Impact of increasing temperatures and exposure duration on egg hatch in the hemlock looper,Lambdina fiscellaria

As the growing season is expected to begin earlier under climate change, insects should initiate reproduction several days or weeks earlier than they used to. In eastern Canada, hemlock looper (HL) Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae) females generally oviposit in September, with eggs entering an obligatory diapause quickly after their deposition. We therefore simulated an early start of the HL reproduction cycle of 2, 4, 6, or 8 weeks to examine the extent to which freshly laid eggs from two populations (island and mainland) can withstand exposure to four temperature conditions (15, 20, 25 °C, or fluctuating temperature in an outdoor insectary), with all treatments ending on 1 September 2007. On this date, half the eggs from each population were immediately incubated at 15 °C, while the rest were stored in an outdoor insectary until their incubation at 15 °C the following spring. In a separate experiment, the effect of temperature on pre‐diapause duration was determined from the number of days required for eggs to change colour after oviposition. The pre‐diapause phase was completed faster as temperature increased. Regardless of incubation date and population, percent hatch decreased significantly after 6‐8 weeks of exposure to 25 °C or in the outdoor insectary. Under most treatments, the odds of dying as pharate larvae increased with exposure duration. When eggs were incubated at 15 °C immediately after treatment, time to hatch and diapause duration remained constant over treatments, except at 25 °C when they both decreased. After 8 weeks of exposure to 15 or 20 °C, eggs transferred outdoors were more likely to hatch precociously than those exposed to 25 °C or insectary conditions. Globally, mortality seemed greater among eggs stored outdoors than among those kept indoors. Most eggs that survived the winter hatched synchronously after incubation in spring. Overall, larger eggs from the island population survived better than smaller eggs from the mainland population.     

Effects of photoperiod and low temperature on diapause termination in the yellow-spotted longicorn beetle (Psacothea hilaris)

Abstract. .The effects of photoperiod and low temperature on diapause termination in the yellow-spotted longicorn beetle, Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae), were examined using a population from Ino, Japan. Diapausing insects obtained by rearing larvae under short daylength (12 or 13 h) at 25^oC were subjected to various treatments. When the photoperiod was changed at the same temperature, diapausing larvae showed a long-day response with a critical daylength between 13.5 and 14h. The diapause was terminated and consequently pupation occurred if the daylength was longer than 13.5 h. Chilling the diapausing larvae at 10^oC for 30 or more days also terminated diapause in most larvae irrespective of the photoperiods during and after chilling treatment. In contrast, the post-chilling photoperiod had a critical effect on development of diapausing larvae chilled for only 15 days.     

Bionomics of the carrot fly (Psila rosae Fab.): II. Soil populations of carrot fly during autumn, winter and spring

The behaviour of the carrot-fly population in the soil during autumn and winter has been investigated in East Anglia over the three seasons 1943-5. The results show that the pest overwinters in both the larval and pupal conditions, and that the proportion of the individuals in each stage varies from crop to crop and from season to season. Samples taken from a May (1943) sown plot showed that pupation, which was 452% complete in October, rose to 742% in March and was not complete until late April. From a June (1944) sown plot of carrots samples showed a rise in percentage pupation from 8-6% in October to 935% in March, the process probably being complete by early April. The changes in proportion of the soil larvae, carrot larvae and puparia in both the May and June plots were followed and are shown graphically. The changes in the size groups of the soil larvae and in the carrot larvae were also traced. The immature larvae persist longer in the carrots than in the soil. The size composition of the larvae from the soil of the June (1944) plot was recorded over the period September to April and the results are given graphically. Samples taken in October 1945 contained highly organized puparia from which flies emerged in a few days. These flies (third generation) gave rise to progeny which overwintered in the larval condition. The population in December 1945, composed chiefly of second generation puparia and third generation larvae, was very similar to that occuring in the previous two years. Mortality in the overwintering carrot-fly larvae and puparia varied considerably but was frequently heavy. The principal agencies concerned were an hymenopterous insect, Dacnusa gracilis Nees., and fungus and bacterial diseases. Other insect parasites occasionally important were Loxotropa tritoma Thorns, and Aleochara sparsa Heer. Nematode parasites were also recorded.     

Dopamine is a key factor for the induction of egg diapause of the silkworm, Bombyx mori.

The silkworm, Bombyx mori, enters diapause in the early embryonic stage. Embryonic diapause is induced by incubating eggs of the maternal generation at high temperature (diapause type), whereas incubation at low temperature results in non-diapausing progeny (non-diapause type). Measurement of catecholamine concentrations in haemolymph and brain-subesophageal ganglia (Br-SGs) showed that only dopamine concentrations in both tissues are consistently higher in diapause-type than non-diapause-type larvae and pupae. In particular, the difference in dopamine concentrations in both tissues increases around pupal ecdysis. During the early pupal stage, Dopa decarboxylase activities and mRNA concentrations in Br-SGs were also much higher in diapause-type than non-diapause-type insects. Elevation of dopamine levels induced by feeding Dopa to penultimate-instar and last-instar larvae, and by injecting Dopa or dopamine into pupae 2 days after pupation made the non-diapause-destined insects lay diapause-destined eggs at 59% and approximately 70% frequencies, respectively. Furthermore, injection of Dopa or dopamine elevated mRNA levels of the diapause hormone in the Br-SGs of non-diapause-type pupae 1 day after injection. Incubation of Br-SGs isolated from non-diapause-type day-2 pupae with Dopa or dopamine also stimulated the expression of diapause hormone mRNA. These data indicate that environmental stimuli during embryonic development increase dopamine levels in both hemolymph and Br-SGs from the larval stage to early pupal stage, which results in laying of diapause-destined eggs by female adults through enhanced expression of the diapause hormone gene.     

Environmental Cues, Endocrine Factors, and Reproductive Diapause in Male Insects

Environmental cues, mostly photoperiod and temperature, mediated by effects on the neuroendocrine system, control reproductive diapause in female insects. Arrest of oocyte development characterizes female reproductive diapause, which has two major adaptive functions: It improves chances of survival during unfavorable season(s), and/or it confines oviposition to that period of the year that is optimal for survival of the eggs and progeny. Although reproductive diapause is less well studied in male insects, there may be no sex-dependent differences in regard to the first of these functions. The second one, however, is not valid for the male; instead, selection pressure directs the male's reproductive strategy toward maximum chances of fertilization of the female's eggs with minimum waste of energy. Therefore, in species with female reproductive diapause, the males may or may not exhibit diapause, but if they do, their diapause must be adapted to that existing in conspecific females. Male reproductive diapause is defined as a reversible state of inability of the male to inseminate receptive females. In relation to reproductive diapause, there are several patterns of coadaptations between male reproductive strategy and timing of female receptivity, (a) In some insects, the females are receptive in the early part of their diapause; mating occurs during this period and there is no diapause in the male. The male dies shortly after copulation and the female stores the sperms to fertilize the eggs that develop after termination of the female's diapause, (b) In some species, as in the grasshopper Anacridium aegyptium, females are receptive during diapause; though oocyte development is arrested, copulation occurs and the stored sperms fertilize the eggs when the female's diapause ends. Males were claimed to have no diapause, but recent studies have revealed the presence of a reproductive diapause in a proportion of the males. This and other cases show that female receptivity during reproductive diapause may or may not be accompanied by male reproductive diapause. If there is a reproductive diapause in the male, it is controlled by the same endocrine mechanism, the corpora allata (CA), as in the females, (c) In many species females are refractory during their diapause. In these cases, males exhibit reproductive diapause, which may be light, as in the beetle Oulema melanopus, or well established, as in certain grasshoppers, butterflies, and beetles. In the latter cases, male diapause is controlled by similar environmental cues (photoperiod, temperature) and by the same intrinsic mechanism (neuroendocrine system, especially CA) as female diapause. Nevertheless, male diapause is less intense; the environmental cues leading to its termination are less complex and/or less extreme, so male diapause terminates before that of the females. Presumably, male diapause is under two antagonistic selection pressures: A male should not waste energy by courting dia-pausing refractory females, but he should be ready to copulate as soon as the females become receptive, otherwise he may lose in the competition between males for females. Some further strategies, which do not seem to fit the above patterns, are also outlined.     

Relationship between photoperiod and secretion of the diapause hormone during larval stages of the silkworm, Bombyx mori L., reared on an artificial diet

The suboesophageal ganglion of the silkworm, Bombyx mori synthesizes sufficient diapause hormone to produce diapause eggs, regardless of the photoperiodic conditions experienced during the larval stages. When larvae destined to produce non-diapause eggs are implanted with the brain-suboesophageal ganglion complex from larvae which have been reared under short-day conditions, the resulting adults lay diapause eggs. The larvae receiving the complex from larvae reared under long-day conditions gave rise to adults which did not produce any diapause eggs. The brains from pupae which have been reared under long-day conditions show an activity inhibiting the secretion of diapause hormone by the suboesophageal ganglion. The mechanism through which the brain controls the secretion of diapause hormone from the suboesophageal ganglion can be modified by photoperiodic conditions during the larval stages.     

A diapause associated protein of the pink bollworm Pectinophora gossypiella Saunders.

A diapause associated protein was electrophoretically isolated from the hemolymph of diapausing last instar larvae of the pink bollworm Pectinophora gossypiella. This protein (M(r) approximately 490,000, glycolipoprotein) was given the name Pectinophora diapause protein (PDP). It is composed of one subunit (M(r) 103,000). The concentration of PDP increased dramatically in the hemolymph of diapausing larvae from 17.4% in prediapause (PD) phase to 29.2% in early diapause (ED) phase reaching a level of 38.6% in larval hemolymph of middiapause (MD) phase. The concentrations of total proteins in the hemolymph of active feeding (A), PD, ED, and MD larvae were 69.8, 106,6, 113.3, and 118 mg/ml, respectively, while those in the fat body of the same larvae were 7.1, 7.4, 8.8, and 4.5 mg/g, respectively. In Pectinophora a drop in the concentration of fat body proteins coincided with a corresponding increase in hemolymph proteins, which suggests an active release of protein from the fat body into the hemolymph during the development of diapause. A partial amino acid sequence of pectinophorin showed the first 15 amino acids starting from the amino terminus of the peptide chain: N-ALA-LYS-THR-ILEU-VAL-GLU-ASN-MET-PRO-PRO-THR-PRO-LEU-ASN-ALA-C.     

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'.     

Maternal influence on the incidence and duration of larval diapause in Calliphora vicina

ABSTRACT. The photoperiodic mechanism governing larval diapause in the blowfly Calliphora vicina R.-D. (Diptera: Calliphoridac) is largely maternal. The critical daylength for adult flies at 20C, and larvae derived from day 12 eggs and maintained in darkness at 11C, is about 14.5 h/24. At short daylength (LD 12:12 h) and a range of temperatures, eggs laid on or before day 9 gave rise to a low incidence of diapause, whereas those laid on day 10 and later gave rise to a high incidence; the photoperiodic 'counter' therefore shows a temperature-compensated mechanism for 'accumulating' successive short days. The rate of switching from non-diapause to diapause progeny is hardly affected by the timing of protein meals, although an early supply of meat accelerates egg development and leads to an increasing proportion of early, non-diapausing progeny. There is no evidence for a maternal effect preventing diapause induction in the first post-diapause ('spring') generation of flies. Diapausing larvae terminate diapause spontaneously in darkness at 11C after a variable period which is positively correlated with the incidence of diapause in the group. Diapause incidence and duration therefore are both determined maternally.