外源保幼激素对中华通草蛉滞育解除及滞育后发育的影响

[目的]本研究旨在明确外源保幼激素(juvenile hormone,JH)在中华通草蛉Chrysoperla sinica滞育快速解除过程中的使用剂量及最佳使用时期.[方法]测定点滴不同剂量(0,5,15,25和35 μg/成虫)外源JH后中华通草蛉滞育成虫的产卵前期、产卵历期、雌虫寿命及单雌产卵量,以及15 μg/...     

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.     

Effects of juvenile hormone analogs and 20-hydroxyecdysone on diapause termination in eggs of Locusta migratoria and Oxya yezoensis

To understand the hormonal control of embryonic diapause, juvenile hormone analogs (JHAs), methoprene and hydroprene, and 20-hydroxyecdysone (20E) were applied onto diapause eggs of Locusta migratoria and Oxya yezoensis. These insects enter diapause at the mid-stage of embryogenesis prior to blastokinesis. Topical application of JHAs significantly facilitated diapause termination in both species but JHA-treated embryos underwent abnormal morphogenesis, pigmentation and sclerotization without dorsal closure. The Locusta eggs immersed in the 20E solution for 24h terminated diapause in a dose-dependent manner. We also investigated phosphorylation of extracellular signal-regulated kinase (ERK), a member of mitogen-activated protein kinase (MAPK), during diapause-terminating process of Locusta migratoria and found that ERK was activated either by cold exposure or JHA treatment. The possible involvement of the hormones and ERK in embryonic diapause and the possibility of ecdysteroids synthesis by prothoracic glands of diapause embryo were proposed.     

Factors influencing the duration and termination of diapause in the Indian-meal moth, Plodia interpunctella

The influence of environmental factors on the duration of diapause in Plodia interpunctella larvae reared in short photoperiods at 20 or 25° C was examined, Diapause terminated most rapidly in long photoperiods at high temperatures. Pupation was more delayed, and mortality was higher, in darkness than in the presence of light. At 20° C, LD 16: 8 hastened diapause termination only slightly in unchilled samples. Chilling for 10 weeks at 10° C greatly reduced the duration of diapause at 20 or 25° C in constant darkness, and rendered LD 16:8 effective in terminating diapause at 20° C. In addition, the quite short duration of diapause under LD 16:8 at 25° C was further shortened by holding for 6–10 weeks at 10° C or below, or by holding in an outbuilding during winter. Holding diapausing larvae at 15 or 20° C proved less effective. Temperature rises from 20 to 25 or 30° C proved effective in terminating diapause. In one stock, the temperature at which diapause was induced influenced its subsequent duration. Lighting conditions during induction had less influence on duration than had temperature, and no difference occurred between pupation times of larvae reared at different population densities, Under all conditions tested, diapause lasted longer in a recently collected field stock than in a laboratory stock.     

Involvement of ERK/MAPK in regulation of diapause intensity in the false melon beetle, Atrachya menetriesi

Embryonic diapause is commonly terminated by exposure to low temperature for a certain duration. Previous studies using the silkworm, Bombyx mori, showed that extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase family, was activated by cold exposure and regulated diapause termination. The involvement of ERK in regulation of diapause termination was investigated in the false melon beetle, Atrachya menetriesi. Embryonic diapause of this beetle is terminated both by cold exposure and by mercury. Phospho-ERK levels remained high during the pre-diapause period but decreased after the eggs entered diapause. Exposure to 7.5 degrees C, which was effective for diapause termination, increased phospho-ERK levels, and these levels were maintained under 7.5 degrees C at least for 100 d. Incubation at 25 degrees C after the eggs were kept at 7.5 degrees C for 20 d, which intensified diapause, decreased the phospho-ERK level. An insufficient cold treatment, i.e., incubation at 0 degrees C for diapause termination did not activate ERK. However, incubation at 0 degrees C after cold treatment at 7.5 degrees C, which is effective for diapause termination, induced high phospho-ERK levels. Moreover, mercury treatment also increased phospho-ERK. Therefore, changes in the phospho-ERK level correlated well with diapause intensity. The results suggest that ERK plays a key role in the regulation of embryonic diapause.     

Influence of methoprene and temperature on diapause termination in adult females of the over-wintering solitary bee, Osmia rufa L

Females of Osmia rufa, as most species in this genus, enter an obligatory diapause, overwintering as an imago inside a cocoon until the ensuing spring when after emergence – mating, egg development and oviposition occur. Diapause in this species is initiated in November, undergoes 2 months of a pre-wintering period that is terminated at the end of January, after 1 month of maintenance. In this study, factors that affect the termination of adult diapause in the female of this species were investigated. The experimental material consisted of bees that were brought from nests kept in natural conditions 1 month prior to natural termination of diapause. Three different experimental treatments were planned to evaluate the potential effect of methoprene and temperature on diapause termination. During the 5 day experimental period the first group of females was kept at 4 °C, the second group at 15 °C and the last group of females was kept at 20 °C. All groups of females were treated with methoprene topically at a dose of 200 μg. After methoprene application a significant increase (p < 0.001) in the size of terminal oocytes was recorded in the three experimental groups. However, no changes in the size of terminal oocytes between acetone treated and untreated control groups were observed. The number of oocytes progressively increased following topical application of methoprene compared to non-treated or acetone treated females. In successive applications of 200 μg methoprene gradual changes in ovary and fat body protein concentration were observed. As compared to controls, protein content in ovaries isolated from methoprene-treated females increased, whereas it decreased in fat body. The least differences in oocyte size and protein concentration in ovary and fat body between control groups and with methoprene application occurred at 4 °C. Differences increased and were higher in females kept at 20 °C and increased rapidly after methoprene application. Exposure to increasing temperature regimes accelerated the juvenile hormone (JH) induced termination of diapause. Taken together, our results indicate that temperature may play an important role in termination of diapause in O. rufa, but its role is secondary to that played by JH.     

Interaction of cyclic nucleotides and ecdysterone in breaking the pupal diapause of the bertha armyworm, Mamestra configurata WLK.

Cyclic GMP and cyclic AMP have distinct and opposite effects upon the action of ecdysterone in diapausing pupae of the Bertha armyworm, $\text{Mamestra}$$\text{configurata}$. Cyclic GMP enhanced the effectiveness of suboptimal doses of ecdysterone in breaking diapause; the amount of cyclic GMP required to lower the ED50 of ecdysterone by half was 80 μg/g. Dibutyryl cyclic GMP had no apparent effect on the action of ecdysterone over a wide dose range (0.07 – 70 μg/g). On the other hand, cyclic AMP and dibutyryl cyclic AMP effectively blocked the diapause-breaking action of ecdysterone when administered simultaneously with the steroid hormone. The amount of cyclic AMP required to reduce the incidence of diapause termination from 100% to 50% was 60 μg/g; for dibutyryl cyclic AMP the amount required was only 14 μg/g. No cyclic nucleotide tested in the study could by itself break the pupal diapause of $\text{M.}$$\text{configurata}$. The concept that cyclic GMP and cyclic AMP provide at least different if not opposing regulatory influences in certain insect systems is discussed briefly in the light of these observations.     

Effects of temperature and photoperiod on termination of pseudopupal diapause in the bean blister beetle, Epicauta gorhami

Larvae of the bean blister beetle, Epicauta gorhami (Coleoptera: Meloidae), feed on grasshopper eggs in soil and undergo hypermetamorphosis. This beetle undergoes larval diapause in the fifth instar as a pseudopupa, a form characteristic of hypermetamorphosis in meloid beetles. This pseudopupal diapause is maintained for a long period if the larvae are kept under continuous diapause-inducing short-day conditions. In the present study, the effects of temperature and photoperiod on termination of pseudopupal diapause in E. gorhami were examined using pseudopupae obtained under 12L-12D at 25°C. Diapause was terminated by exposure to low or high temperature, but not by transfer to long-day conditions. The pseudopupal stage comprises diapause and post-diapause phases despite its unchanging appearance. The optimum low temperature for diapause termination was 10-15°C, and a higher or lower temperature was less effective. There was an individual variation in the low temperature requirement for diapause termination and post-diapause development may not occur until this requirement is satisfied. Although under natural conditions pseudopupae may encounter low temperatures that are effective for diapause termination at different ages, our results show that pseudopupae at various ages respond similarly to low temperature exposure. This response may ensure that resumption of development synchronizes in a population.     

Low temperature storage of larvae and synchronization of adult emergence in the predatory midge Aphidoletes aphidimyza.

Diapause larvae of Aphidoletes aphidimyza were stored at a temperature of 3 degrees C under continuous darkness for up to 7 months with survival rates above 50%; after storage for 1 year the survival rate dropped to 12%. Diapause was terminated in the majority of individuals within 120 days of chilling under storage conditions. Brief exposure (10-60 s) to the vapor of n-hexane appeared to be a useful alternative to chilling for the termination of diapause. The larvae with terminated diapause required, on average, an additional 31 days at 22 degrees C and long-day conditions in order to reach the adult stage. The 10-90% adult emergence spanned a period of 21.1 days. When the larvae with terminated diapause were exposed to 30 degrees C for 1 week after the end of low temperature storage, the survival rate was not affected, the average "time-to-adult" shortened moderately to 28 days, and the synchrony of adult emergence improved considerably to 10 days. Low temperature storage of nondiapause larvae resulted in a decrease in survival from 98 to 31% during the first 60 days of storage. Nondiapause larvae did not enter diapause during low temperature storage and, as a consequence, the adults emerged relatively rapidly (after 14-15 days) and synchronously (within 2-3 days) after the end of storage. Directions for future research, which might bring further improvement in low temperature storability and synchrony of adult emergence in A. aphidimyza, are proposed.     

Factors influencing the duration and termination of diapause in the Warehouse moth, Ephestia elutella

The influence of environmental factors on the duration of diapause was evaluated in larvae of Ephestia elutella (Hübner) reared in short photo-periods at 25C or below. Termination of diapause was hastened by long photoperiods, high temperatures, long periods at low temperature, or exposure to fumigants. Diapause terminated rapidly under long photoperiods at 30 or 25C, but not at 20C. The critical photoperiod for the termination of diapause was similar to that for induction, lying between 13 and 16 h at 25C. The longest duration of diapause occurred in constant darkness (DD) at 20C. However, batches of larvae reared at 20C in DD pupated a little sooner than batches reared under LD, if both were transferred at the start of diapause to warm, long-day conditions. Long exposure to low temperature reduced the number of long photoperiods necessary for the rapid termination of diapause at high temperature. Samples of larvae brought to the laboratory at monthly intervals from an unheated outbuilding in which they were overwintering, required an average of c. 200 days to pupate in DD at 25C when transferred in December, compared with only 32 days when transferred in February or March. By comparison, batches transferred to LD 16:8 at 25C required 39 days when transferred in December and 20–24 days in February and March. Holding at low temperature for long periods also encouraged synchronous emergence of the sexes. Duration of diapause was generally shorter in a laboratory stock than in a stock collected from the field.     

Ecdysteroids and adult diapause in the Colorado potato beetle, Leptinotarsa decemlineata

ABSTRACT. The difference in ecdysteroid activity in short-day (10-h photo-phase) and long-day (16-h photophase) Leptinotarsa decemlineata Say adults was characterized by high performance liquid chromatography, which revealed that for short-day beetles ecdysterone and ecdysone are the major constituents of the free ecdysteroids, whereas in long-day beetles products co-migrating with 2-deoxyecdysone and 2-deoxyecdysterone are just as abundant. Ecdysteroids were detected (15 ng/ml) only in the haemolymph of females. Ligation experiments showed that the induction of the diapause syndrome by inactivation of the corpora allata or the brain not only resulted in the formation of the typical diapause proteins but also in an increase of the ecdysteroid activity. It is suggested that adult diapause in L.decemlineata is regulated by a multifactorial system.     

Preventing insect diapause with hormones and cholera toxin

The decision to enter pupal diapause can be reversed in the flesh fly $\text{Sarcophaga crassipalpis}$ by treatment with a juvenile hormone analogue, ecdysterone, or cholera toxin. A topical application of juvenile hormone analogue (10μg) is effective in preventing diapause if applied to newly ecdysed 3rd instar larvae. An ecdysterone injection (1μg) into post-fed 3rd instar larvae can avert diapause, and even lower dosages (0.01μg) are effective if injected into young pupae immediately before the onset of diapause. Cholera toxin, a stimulant of adenylate cyclase, can prevent diapause if 1μg is injected into larvae 24 hrs. prior to pupariation. This is the first report of an effect of cholera toxin on insects. A 2-day exposure to 33°C was the only physical manipulation shown to be capable of reversing the previous commitment to enter pupal diapause.     

Effect of anoxia on diapause termination in eggs of the false melon beetle, Atrachya menetriesi

The effect of anoxia on diapause development in the leaf beetle Atrachya menetriesi was investigated to elucidate the role of oxygen in regulation of egg diapause. While anoxia alone had no effect on diapause termination, it decreased diapause intensity before chilling. Such an effect reached a maximum level when anoxia lasted for about 10 days. Anoxia applied during the pre-diapause stage also reduced diapause intensity. On the other hand, anoxia terminated diapause when the diapause intensity had been lowered by sufficient duration of chilling (50 days at 7.5 degrees C). The effect of anoxia was temperature dependent; the larger effect was elicited when anoxia was combined with a higher temperature. A 50-day chilling caused more than 20% of eggs to terminate diapause upon transfer to warm conditions. However, when this chilling period was interrupted on the 20th day by a 5-day exposure to a high temperature of 20, 25 or 30 degrees C, the effect of the former chilling was cancelled partially or completely, suggesting that warming reversed diapause development. This reversing effect of a high temperature, however, was not manifested when the warming was combined with anoxia. The results suggest that anoxia inhibits diapause reversal and facilitates a certain process of diapause development. The sequence of exposure to anoxia and chilling is not important.     

Geographic variation in diapause induction and termination of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Overwintering diapause in Helicoverpa armigera, a multivoltine species, is controlled by response to photoperiod and temperature. Photoperiodic responses from 5 different geographical populations showed that the variation in critical photoperiod for diapause induction was positively related to the latitudinal origin of the populations at 20, 22 and 25 °C. Diapause response to photoperiod and temperature was quite different between northern and southern populations, being highly sensitive to photoperiod in northern populations and temperature dependence in southern populations. Diapause pupae from southern population showed a significantly shorter diapause duration than from northern-most populations when they were cultured at 20, 22, 25, 28 and 31 °C; by contrast, overwintering pupae from southern populations emerged significantly later than from northern populations when they were maintained in natural conditions, showing a clinal latitudinal variation in diapause termination. Diapause-inducing temperature had a significant effect on diapause duration, but with a significant difference between southern and northern populations. The higher rearing temperature of 22 °C evoked a more intense diapause than did 20 °C in northern populations; but a less intense diapause in southern population. Cold exposure (chilling) is not necessary to break the pupal diapause. The higher the temperature, the quicker the diapause terminated. Response of diapause termination to chilling showed that northern populations were more sensitive to chilling than southern population.     

The initiation of adult development in Sarcophaga argyrostoma by β-ecdysone

Sarcophaga argyrostoma pupae otherwise destined to diapause can be made to initiate prompt, complete adult development by injection of 0.2 to 0.3 μg β-ecdysone/g body weight, if the injection is given soon after head eversion at the time ecdysone levels would normally increase in developing animals. At these doses some animals show only the earliest signs of adult development and then enter diapause. After two weeks in diapause, a 40-fold higher dose (10 μg/g) is required to initiate development promptly. β-ecdysone can also accelerate the termination of diapause after a time delay which is dose-dependent. Doses of 6 to 10 μg/g lead to hyperhormonal abnormalities affecting antennae, genitalia, and bristle orientation.     

Diapause termination in the spotted stem borer, Chilo partellus (Lepidoptera: Pyralidae) in the laboratory

The effect of temperature, photoperiod, artificial diet and water on the termination of diapause by larvae of the stem borer, Chilo partellus (Lepidoptera: Pyralidae), was studied in the laboratory. Termination of diapause as indicated by pupation was affected mainly by a combination of high temperature and a long day photoperiod. Total darkness did not prevent termination of diapause and pupation occurred also in larvae which were never exposed to water. Long days accelerated pupation, but, under 16 h daylength, termination of diapause was faster than under constant illumination. Provision of artificial diet had no effect or slowed down pupation but water decreased the time to pupation. Under 28°C, 16 h daylength and availability of water, C. partellus diapausing larvae terminated diapause and pupated in about 9 days.     

Effects of nutrition and methoprene treatment upon reproductive diapause in Caloptilia fraxinella (Lepidoptera: Gracillariidae)

Abstract Female Caloptilia fraxinella exhibit a prolonged reproductive diapause immediately post adult emergence in mid‐summer until the next spring when mating, egg development and oviposition on fresh Fraxinus spp. leaflets occur. Factors that effect the termination of reproductive diapause are investigated in this species. Caloptilia fraxinella diapausing adults held in overwintering conditions (2 °C, LD 0 : 24 h) for 24 weeks terminate diapause after placement for 2 weeks in simulated summer conditions (24 °C, LD 16 : 8 h) only if they are provided with 10% sugar water. Exogenous application of the Juvenile Hormone (JH) analogue methoprene to moths in both early‐ (summer) and mid‐ (autumn) reproductive diapause demonstrates that JH affects diapause termination but a carbohydrate nutrition source also mediates mating and vitellogenesis. Mating between moth pairs early in diapause occurs only after treatment with methoprene and provision with sugar water. However, there is no impact of mating on the propensity of females to produce vitellogenic oöcytes. Moths collected in the autumn in mid‐diapause respond in a dose‐dependent fashion to methoprene treatment and the response is greater than that of moths early in diapause collected in the summer. Treatment with methoprene and access to sugar water results in vitellogenic oöcytes in 18.75% of females from mid‐diapause moth pairs treated with 0.01 μg methoprene per insect and in all females from pairs treated at the two highest doses of methoprene (0.1 and 1 μg per insect). Mating occurs only between moths in mid‐diapause treated with the two highest doses of methoprene and these doses induce 91% and 100% mating, respectively. Both control and methoprene‐treated males in mid‐diapause held under summer conditions mate successfully and pass a spermatophore to their methoprene‐treated female partner. These data demonstrate that female C. fraxinella undergo a prolonged reproductive diapause in which termination is dependent on JH and further mediated by a carbohydrate nutrition source. The production of vitellogenic oöcytes is independent of mating. These data also provide evidence that response of moths in diapause to exogenous applications of methoprene differs throughout the diapause period and between male and female C. fraxinella.     

Diapause termination in two species of tropical butterfly, Euploea core (Cramer) and Euploea sylvester (Fabricius) (Lepidoptera: Nymphalidae)

Abstract This study examined the factors used as cues for diapause termination by two Euploea species. Euploea core and E. sylvester were collected from two overwintering sites at Chillagoe, Queensland. Under tropical wet-season conditions, more butterflies terminated diapause (approximately 60%) than those kept under dry-season conditions (approximately 40%). However, 100% diapause termination occurred only when butterflies were kept under wet-season conditions and were fed with honey. For reproductive success, Euploea species need to terminate diapause rapidly to synchronise oviposition with fresh, rapid growth of their larval host plants, which often occurs after rain. The presence of rainfall, increased temperature and long days alone is not a fail-safe set of cues for this event. Our results suggest that food (as nectar), in conjunction with these combined environmental factors, provide Euploea species with a reliable signal that larval host resources are available for oviposition.