Prothoracicotropic hormone activity in the embryonic brain of the tobacco hornworm,Manduca sexta

Summary Head segments and brains were extirpated from embryos of the tobacco hornworm,Manduca sexta, extracted and the resulting extracts assayed for prothoracicotropic hormone (PTTH) activity on prothoracic glands from day 3 fifth instar larvae and day 0 pupae. Dose-response curves were generated and indicated the presence of PTTH activity in embryonic brains and head segments, suggesting a role(s) for this neurohormone during embryogenesis. Maximal PTTH activity was found in brains from embryos 117 h post-oviposition, just prior to hatching, but activity was also noted in head segments as early as 24 h postoviposition. These data on PTTH and those on ecdysteroids and juvenile hormones in embryos suggest that these 3 classes of hormones which control insect post-embryonic development, may also be involved in the regulation of developmental processes in the embryo.     

Characterization of HSP27 and three immunologically related polypeptides during Drosophila development

The low-molecular-weight heat-shock protein HSP27 is made in the absence of heat shock during Drosophila melanogaster development. An analysis of the accumulation of HSP27 during specific stages of development is presented using an antiserum recognizing this protein. Whereas HSP27 is abundant during embryogenesis, the level of this protein begins to decrease in the 20-h old embryo and is no longer detectable in second instar larvae. A high level of HSP27 is again observed in third instar larvae and reaches a maximal level in late pupae. While still abundant in young adult flies of both sexes, a greater amount of HSP27 is found in females with the protein being highly concentrated within the ovaries. Following lysis of whole pupae, about 60% of HSP27 is found in the soluble lysate fraction in a form which sediments between 5 and 20 S. Anti-HSP27 serum also recognizes three other developmentally regulated polypeptides with apparent MW of 33, 85 and 120 kDa. The 33 kDa protein accumulates in pupae while those of 85 and 120 kDa are more abundant in third instar larvae. Unlike HSP27, these proteins are not detected in embryos or ovaries. Immunoblot analysis of V8 proteolytic fragments suggests that HSP 27 and 33 kDa are related polypeptides. Exposure of the developing insect to heat-shock treatment results in increased level of HSP27. In larvae, a small amount of the 33 kDa protein accumulates following heat shock, while in pupae and adult flies a decrease in the concentration of this protein is observed after heat shock. Finally, different cellular localizations and distributions within the pupal body have been found for these developmentally regulated polypeptides.     

Ergatoid queen development in the ant Myrmecina nipponica: modular and heterochronic regulation of caste differentiation

Caste polyphenism in social insects provides us with excellent opportunities to examine the plasticity and robustness underlying developmental pathways. Several ant species have evolved unusual castes showing intermediate morphologies between alate queens and wingless workers. In some low-temperature habitats, the ant Myrmecina nipponica produces such intermediate reproductives (i.e. ergatoids), which can mate and store sperm but cannot fly. To gain insight into the developmental and evolutionary aspects associated with ergatoid production, we conducted morphological and histological examinations of the post-embryonic development of compound eyes, gonads and wings during the process of caste differentiation. In compound eyes, both the queen-worker and ergatoid-worker differences were already recognized at the third larval instar. In gonads, queen-worker differentiation began at the larval stage, and ergatoid-worker differentiation began between the prepupal and pupal stages. Wing development in ergatoids was generally similar to that in workers throughout post-embryonic development. Our results showed that the developmental rate and timing of differentiation in body parts differed among castes and among body parts. These differences suggest that the rearrangement of modular body parts by heterochronic developmental regulation is responsible for the origination of novel castes, which are considered to be adaptations to specific ecological niches.     

Developmental Arrest and Ecdysteroid Deficiency Resulting from Mutations at the Dre4 Locus of Drosophila

Loss-of-function mutations of the dre4 gene of Drosophila melanogaster caused stage-specific developmental arrest, the stages of arrest coinciding with periods of ecdysteroid (molting hormone) regulated development. Nonconditional mutations resulted in the arrest of larval development in the first instar; embryogenesis was not impaired, and mutant larvae were behaviorally normal and long-lived. At 31 degrees the temperature-sensitive dre4e55 allele caused the arrest of larval development in the first or second instars. When upshifted to 31 degrees at various times during development, dre4e55 mutants exhibited nonpupariation of third-instar larvae, failure of pupal head eversion, failure of adult differentiation, or noneclosion of pharate adults. Under some temperature regimens second-instar larvae pupariated precociously without entering the normally intervening third-instar. Nonpupariation and defects in metamorphosis were associated with the reduction or elimination of ecdysteroid peaks normally associated with late-larval, prepupal, pupal and pharate adult development. Ecdysteroid production by larval ring glands from dre4e55 hemizygous larvae was suppressed after 2 hr of incubation in vitro at 31 degrees, indicating autonomous expression of the dre4 gene in the ring gland. We postulate that the dre4 gene is required for ecdysteroid production at multiple stages of Drosophila development and that the pathologies observed in dre4 mutants reflect developmental consequences of ecdysteroid deficiency.     

Cellular localization of HSP23 during Drosophila development and following subsequent heat shock

The low-molecular-weight heat-shock protein HSP23 is synthesized in the absence of heat shock during Drosophila development. Here, I present a quantitative analysis of this phenomenon and describe the cellular localization of this protein during normal development and after a subsequent heat shock. HSP23 is first detected in the late third instar larvae and continues to accumulate reaching a maximum level in late pupae. In a 1-week-old adult, HSP23 can no longer be detected. Following lysis of whole pupae, HSP23 is found in the soluble lysate fraction in a form which sediments between 10 and 20 S. Exposure of larvae, pupae, and the adult fly to heat stress (37 degrees C) results in an increased amount of HSP23 which, however, is recovered in an insoluble particulate form following insect lysis. During recovery from heat shock, HSP23 is again found in the soluble 10- to 20-S lysate fraction. In pupae which are exposed to a severe heat stress (41 degrees C) HSP23 remains in the pellet fraction after the heat stress and no pupae are able to emerge as adult flies. However, when pupae are first exposed to a mild heat-shock treatment prior to the 41 degrees C stress, the thermotolerance process is induced and HSP23 is again rapidly found in the soluble lysate fraction during the recovery from heat shock. These observations suggest a possible correlation between the survival of pupae after heat shock and the recovery of HSP23 in the soluble lysate fraction as 10- to 20-S structures after the heat shock.     

The effect of temperature on the development and life cycle regulation of the pine weevil Hylobius abietis and the potential impacts of climate change

• 1 The pine weevil Hylobius abietis is widely distributed in the Palaearctic region where it is a major pest. Although predominantly semi‐voltine, with a 2‐year life cycle, the generation time across its range can vary from 1 to 4 years. The duration of the life cycle and the seasonal timing of weevil activity affect the economic impact and management of this pest, all of which are likely to change in a warming climate.
• 2 To determine the effect of temperature and tree species on weevil growth and development, laboratory experiments were performed with eggs, larvae, prepupae, pupae and adults, using, as appropriate, the host species Scots pine Pinus sylvestris L. and Sitka spruce Picea sitchensis (Bong.) Carr. under constant or alternating temperatures.
• 3 The development rate was linearly related to temperature, with developmental thresholds for eggs, larvae and pupae of 8, 4.5 and 7.3 °C, respectively. Day‐degrees were estimated for each life stage. Larval development was affected by tree species, being slower on Sitka spruce than on Scots pine, and was faster under alternating than constant temperatures.
• 4 The development time for prepupae was highly variable, with an apparent facultative prepupal diapause initiated by temperature. The temperature range 20–17.5 °C marked the transition between median prepupal development times of approximately 25 and 90 days. The prepupal stage may serve to minimize the risk of overwintering mortality in the pupal stage and help to synchronize the life cycle.
• 5 Larval and adult mass was positively related to developmental temperature, demonstrating an inverse temperature size rule, and weevils were heavier when developing on Scots pine than Sitka spruce. Development in alternating temperatures reduced weevil mass on Scots pine. The influence of temperature on weevil mass is likely to have a positive effect on fecundity and overwintering survival. The effects of climate change on development, voltinism and weevil mass are discussed.

     

幼虫密度对甜菜夜蛾生长发育与繁殖的影响

为了研究甜菜夜蛾Spodoptera exigua(Hübner)幼虫的密度对其发育及繁殖的影响,本实验观察了5种幼虫密度下（1,5,10,20,30头/瓶）,幼虫发育和成虫繁殖情况。结果表明：幼虫和蛹历期、存活率和蛹重均差异显著。幼虫和蛹历期均以20头/瓶的最短,1头/瓶的最长,其余随幼虫密度增加而延长;幼虫至蛹存活率以10头/瓶的最高,其余随幼虫密度增加而降低;1头/瓶的蛹最重,显著高于其他密度的,其余随幼虫密度增加而下降。尽管密度间成虫羽化率和产卵前期均无显著差异,但成虫产卵量、寿命和畸形率差异显著。1头/瓶的产卵量最多,其次为10头/瓶的,其余随幼虫密度增加而减少,30头/瓶的产卵量显著少于其他密度的; 密度在1～20头/瓶范围内,雌蛾寿命均较短,显著短于30头/瓶的,而雄蛾寿命以5头/瓶的最短,显著短于其他密度的（10头/瓶除外）,10头/瓶的次之,其余密度间差异不显著;不同幼虫密度下羽化的成虫畸形率差异显著,10头/瓶的最低,其余随幼虫密度增加而升高; 生命表结果表明甜菜夜蛾在10头/瓶下世代存活率和种群增长指数均最高,幼虫密度过低或过高均不利于种群增长;世代存活率（S）和种群增长指数（I）与幼虫密度之间的关系均呈抛物线关系：S =－0.2087x²+2.5694x+211.52 (R²=0.88),I=－0.0552x²+0.9166x+54.168 (R²=0.95)。结果提示幼虫密度影响甜菜夜蛾种群动态的重要生态因子之一。     

滞育和非滞育棉铃虫血淋巴类固醇蜕皮素含量变化的比较

采用放射免疫分析法对不同时期的注定滞育和非滞育棉铃虫的血淋巴中的类固醇蜕皮素的含量进行了测定,发现在预蛹期间,注定滞育的棉铃虫的类固醇蜕皮素含量高于非滞育的棉铃虫,化蛹后,注定滞育的棉铃虫的类固醇蜕皮素含量则迅速降到极低的水平,明显低于非滞育棉铃虫。用20-羟基蜕皮素处理不同时期的滞育蛹,均能打破滞育。由此可见,类固醇蜕皮素含量的降低或缺乏乃是导致棉铃虫滞育的关键因子之一。     

Effects of a juvenoid, DPE-28, on biology and behaviour of Culex quinquefasciatus, the human filariasis vector

Studies on the effect of a juvenoid, DPE-28 (2,4-dinitrophenyl-2',6'-di-tertiarybutyl phenyl ether) on biology and behaviour of Cx. quinquefasciatus showed that the developmental duration, sex ratio, mating success and blood feeding were considerably affected by the exposure of larvae and pupae to the compound. Exposure of fourth instar larvae to 0.007 (EI90) and 0.0019 (EI50) ppm of DPE-28 prolonged the duration of pupation by 58.6 and 52.4 hr and delayed the adult emergence by 35.4 and 17.7 hr in males and 36.8 and 21.1 hr in females respectively. Exposure of freshly ecdysed pupae to 10 and 5 ppm delayed the adult emergence with respect to the control by 54.3 and 32.4 hr in males and 55.2 and 33.2 hr in females respectively. The sex ratio of the adults emerged from treated larvae and pupae was also affected. The female mosquitoes that survived from the exposed fourth instar larvae and pupae exhibited a low blood engorgement ratio. This depression in blood feeding was more pronounced in adults emerged from treated pupae than that of treated fourth instar larvae. A significant proportion of adults emerged from treated larvae and pupae were able to feed only partially. Mating success of the treated populations declined considerably when crosses were made between the males and females emerged from treated fourth instar larvae and pupae. The adults emerged from treated larvae and pupae showed a significant reduction in the oviposition.     

Rhomboid Enhancer Activity Defines a Subset of Drosophila Neural Precursors Required for Proper Feeding,Growth and Viability

Organismal growth regulation requires the interaction of multiple metabolic, hormonal and neuronal pathways. While the molecular basis for many of these are well characterized, less is known about the developmental origins of growth regulatory structures and the mechanisms governing control of feeding and satiety. For these reasons, new tools and approaches are needed to link the specification and maturation of discrete cell populations with their subsequent regulatory roles. In this study, we characterize a rhomboid enhancer element that selectively labels four Drosophila embryonic neural precursors. These precursors give rise to the hypopharyngeal sensory organ of the peripheral nervous system and a subset of neurons in the deutocerebral region of the embryonic central nervous system. Post embryogenesis, the rhomboid enhancer is active in a subset of cells within the larval pharyngeal epithelium. Enhancer-targeted toxin expression alters the morphology of the sense organ and results in impaired larval growth, developmental delay, defective anterior spiracle eversion and lethality. Limiting the duration of toxin expression reveals differences in the critical periods for these effects. Embryonic expression causes developmental defects and partially penetrant pre-pupal lethality. Survivors of embryonic expression, however, ultimately become viable adults. In contrast, post-embryonic toxin expression results in fully penetrant lethality. To better define the larval growth defect, we used a variety of assays to demonstrate that toxin-targeted larvae are capable of locating, ingesting and clearing food and they exhibit normal food search behaviors. Strikingly, however, following food exposure these larvae show a rapid decrease in consumption suggesting a satiety-like phenomenon that correlates with the period of impaired larval growth. Together, these data suggest a critical role for these enhancer-defined lineages in regulating feeding, growth and viability.     

Differences in heat shock protein 70 expression during larval and early spat development in the Eastern oyster, Crassostrea virginica (Gmelin, 1791)

For a variety of species, changes in the expression of heat shock proteins (HSP) have been linked to key developmental changes, i.e., gametogenesis, embryogenesis, and metamorphosis. Many marine invertebrates are known to have a biphasic life cycle where pelagic larvae go through settlement and metamorphosis as they transition to the benthic life stage. A series of experiments were run to examine the expression of heat shock protein 70 (HSP 70) during larval and early spat (initial benthic phase) development in the Eastern oyster, Crassostrea virginica. In addition, the impact of thermal stress on HSP 70 expression during these early stages was studied. C. virginica larvae and spat expressed three HSP 70 isoforms, two constitutive, HSC 77 and HSC 72, and one inducible, HSP 69. We found differences in the expression of both the constitutive and inducible forms of HSP 70 among larval and early juvenile stages and in response to thermal stress. Low expression of HSP 69 during early larval and spat development may be associated with the susceptibility of these stages to environmental stress. Although developmental regulation of HSP 70 expression has been widely recognized, changes in its expression during settlement and metamorphosis of marine invertebrates are still unknown. The results of the current study demonstrated a reduction of HSP 70 expression during settlement and metamorphosis in the Eastern oyster, C. virginica.     

The 30kP protease A responsible for 30-kDa yolk protein degradation of the silkworm, Bombyx mori: cDNA structure, developmental change and regulation by feeding

We have cloned and sequenced the cDNA encoding the major component (43-kDa peptide) of 30kP protease A which selectively hydrolyzes 30-kDa yolk proteins of the silkworm, Bombix mori. The deduced amino acid sequence consisted of 318 amino acids and shared sequences conserved in many serine proteases. Northern blot analysis using the cDNA as probe revealed that 43-kDa peptide mRNA began to rise at the last phase of embryogenesis and reached a maximum level at larval hatching. This level was maintained with some fluctuations throughout post-embryonic development. The concentration of 43-kDa peptide increased greatly toward larval hatching coinciding with the changing pattern of mRNA. When larvae were fed, the peptide concentration abruptly decreased and remained near zero throughout post-embryonic development. The decrease in peptide concentration did not occur, however, when the hatched larvae were starved. Thus, the nutritional shift from endogenous yolk to exogenous food plays a key role in 30kP protease A elimination from neonate larvae.     

Cathepsin L is essential for embryogenesis and development of Caenorhabditis elegans.

Cysteine proteases play critical biological roles in both intracellular and extracellular processes. We characterized Ce-cpl-1, a Caenorhabditis elegans cathepsin L-like cysteine protease. RNA interference with Ce-cpl-1 activity resulted in embryonic lethality and a transient delayed growth of larvae to egg producing adults, suggesting an essential role for cpl-1 during embryogenesis, and most likely during post-embryonic development. Cpl-1 gene (Ce-cpl-1:lacZ) is widely expressed in the intestine and hypodermal cells of transgenic worms, while the fusion protein (Ce-CPL-1::GFP) was expressed in the hypodermis, pharynx, and gonad. The CPL-1 native protein accumulates in early to late stage embryos and becomes highly concentrated in gut cells during late embryonic development. CPL-1 is also present near the periphery of the eggshell as well as in the cuticle of larval stages suggesting that it may function not only in embryogenesis but also in further development of the worm. Although the precise role of Ce-CPL-1 during embryogenesis is not yet clear it could be involved in the processing of nutrients responsible for synthesis and/or in the degradation of eggshell. Moreover, an increase in the cpl-1 mRNA is seen in the intermolt period approximately 4 h prior to each molt. During this process Ce-CPL-1 may act as a proteolytic enzyme in the processing/degradation of cuticular or other proteins. Similar localization of a related cathepsin L in the filarial nematode Onchocerca volvulus, eggshell and cuticle, suggests that some of the Ce-CPL-1 function during development may be conserved in other parasitic nematodes.     

Role of the brain and ring gland in regulation of pupal diapause in the flesh fly Sarcophaga crassipalpis

Larvae of Sarcophaga crassipalpis photoperiodically programmed for pupal diapause pupariate later than larvae programmed for continuous development. Pupariation time is determined by the brain-ring gland complex as evidenced by transplantation experiments in which the timing of pupariation was transferred from one larva to another by transplantation of the brain-ring gland complex. The developmental commitment (diapause or nondiapause) of the larva also can be transferred with the brain-ring gland complex if the recipient's own neuroendocrine system is suppressed by ring gland extirpation. Thus, photoperiodic programming of the brain-ring gland complex is not only responsible for developmental commitment but also for determining the duration of the prepupal period. Surgical experiments with pupae indicate that an intact brain-ring gland complex is required for diapause termination and initiation of adult development. Pupae fail to break diapause if either the brain or the ring gland is removed or if their nervous connections are severed.     

The effect of a juvenile hormone analogue on ecdysteroid titre during development and HnRNA formation in the moth,Ephestia cautella

The juvenile hormone analogue, methoprene was found to interfere with normal development of Ephestia in a manner dependent on age. Young embryos, prior to the stage of blastokinesis, and animals, shortly before and after pupation, were found to be the most sensitive to the compound. The JHA inhibited metamorphosis and produced giant larvae when it was given to immature larvae, however, when it was given to larvae 2–3 days prior to pupation or to young pupae it did not affect metamorphosis but prevented adult emergence. Comparison of the ecdysteroid titre determined in control and treated animals in the various developmental stages showed that JHA depressed the ecdysteroid titre totally only when it was given to young larvae and partially when it was applied shortly before pupation. It seems that the action of methoprene on ecdysone regulated systems and/or ecdysone producing systems in Ephestia appears to be mainly during the larval stage prior to the appearance of the small ecdysteroid peak and the formation of HnRNA in the transition period from larvae to pupae.     

Resistance to thermal stress in preadult Drosophila buzzatii: variation among populations and changes in relative resistance across life stages

Resistance to a short term exposure to a high temperature stress was examined in eggs, larvae and pupae of Drosophila buzzfltii from seven localities. Across development, pupae were most resistant, followed by eggs, and then first and third-instar larvae. Variation among populations for resistance to heat stress was significant in all life stages. However, there was much less variation among populations where measured as eggs and pupae than for both first and third instar larvae. Older larvae showed large changes both in viability and developmental time, while exposure of young larvae to heat stress led to a decline in viability without delayed development. Populations that had the shortest developmental time at 25^oC were relatively the most resistant to heat stress as larvae. High relative resistance at one preadult life stage was not necessarily associated with relatively high resistance at another, or with previous measurements of resistance for adults from these populations. Comparison of populations that were more similar in their pattern of change in resistance across development suggested a relationship with the climate of origin. The possibility that developmental variation in the expression of heat shock proteins may cause variation in resistance to thermal stress for different life stages is discussed.