Larval Body Mass Research Articles

Effects of ozone and ammonium sulfate on cauliflower: Emphasis on the interaction between plants and insect herbivores

Ammonium sulfate [(NH4)2SO4] deposition and elevated ozone (O3) concentrations may negatively affect plants and trophic interactions. This study aimed to evaluate for the first time the interactive effects of high (NH4)2SO4 load and elevated O3 levels on cauliflower (Brassica oleracea L.) under field conditions. Cauliflower seedlings were treated with 0 (AS0) or 50 (AS50) kg ha−1 (NH4)2SO4 and exposed to ambient (AOZ, ≈20 ppb) or elevated (EOZ, ≈55 ppb) O3 for about one month, in a Free Air O3 Concentration Enrichment (FACE) system. The oligophagous diamondback moth (Plutella xylostella Linnaeus, 1758) showed a clear preference towards the seedlings treated with AS50, which intensively grazed. Plant-herbivore interactions were driven by (NH4)2SO4 availability, rather than O3, via increased nitrogen content in the leaves. Further laboratory bioassays were followed to confirm the validity of these observations using polyphagous Eri silkmoth larvae (Samia ricini) as a biological model in a standardized experimental setup. Choice assays, where larvae could select leaves among leaf samples from the different experimental conditions, and no-choice assays, where larvae could graze leaves from just one experimental condition, were conducted. In the choice assay, the larvae preferred AS50-treated leaves, in agreement with the field observations with diamondback moth. In the no-choice assay, larval body mass growth was inhibited when fed with leaves treated with EOZ and/or AS50. Larvae fed with AS50-treated leaves displayed increased mortality. These observations coincide with higher NO3 and Zn content in AS50-treated leaves. This study shows that plant-herbivore interactions can be driven by (NH4)2SO4 availability, independently of O3, and suggests that high N deposition may have severe health implications in animals consuming such plant tissues.Key message: Plant-herbivore interactions are driven by high (NH4)2SO4 availability, independently of O3.

What is the optimal treatment time for larval therapy? A study on incubation time and tissue debridement by bagged maggots of the greenbottle fly, Lucilia sericata.

The effective use of larvae of the greenbottle fly, Lucilia sericata, in wound debridement requires a working knowledge of how feeding changes over time. Using a laboratory assay and bagged larval dressings, the effect of incubation time on larval feeding rates and body mass was investigated for up to 120 hours at 32°C. The mass of tissue digested increased significantly in incremental 24-hour periods up to 72 hours, with no significant consumption occurring afterwards. Larval mass increased only up to 48 hours. A further test comparing the efficacy of a single 96-hour application of larvae against two consecutive 48-hour applications found that the mass of tissue digested in the latter was 14.3% higher than the former, a difference that was statistically significant. Current clinical guidance suggests a 4-day application period for bagged larvae. Based on these results, an incubation time of 72 hours (3 days) for bagged larvae would be the most effective at the study temperature. However, it is acknowledged that wound temperature can vary, whereby feeding rates would likely differ. In view of this, we conclude that a period of 3 to 4 days is optimum for the application of larvae, and current guidelines should be adhered to.

Social and nutritional factors shape larval aggregation, foraging, and body mass in a polyphagous fly

The majority of insect species have a clearly defined larval stage during development. Larval nutrition is crucial for individuals’ growth and development, and larval foraging success often depends on both resource availability and competition for those resources. To date, however, little is known about how these factors interact to shape larval development and behaviour. Here we manipulated the density of larvae of the polyphagous fruit fly pest Bactrocera tryoni (‘Queensland fruit fly’), and the diet concentration of patches in a foraging arena to address this gap. Using advanced statistical methods of machine learning and linear regression models, we showed that high larval density results in overall high larval aggregation across all diets except in extreme diet dilutions. Larval aggregation was positively associated with larval body mass across all diet concentrations except in extreme diet dilutions where this relationship was reversed. Over time, larvae in low-density arenas also tended to aggregate while those in high-density arenas tended to disperse, an effect that was observed for all diet concentrations. Furthermore, larvae in high-density arenas displayed significant avoidance of low concentration diets – a behaviour that was not observed amongst larvae in low-density arenas. Thus, aggregation can help, rather than hinder, larval growth in high-density environments, and larvae may be better able to explore available nutrition when at high-density than when at low-density.

Food utilization and excretion mechanism of Cd in gypsy moth larvae fed on Cd-enriched Populus albaXP. berolinensis leaves

To investigate the eco-physiological responses of phytophagous insects to host plants exposed to heavy metal stress, the gypsy moth (Lymantria dispar) larvae were reared with leaves of Populus albaXP. berolinensis grown in Cd-contaminated soil to analyze their food utilization and mechanisms underlying Cd excretion. Our results showed that after feeding on Cd-stressed poplar leaves, Cd concentrations and contents in the 3rd-6th instar larvae were significantly higher than those in control. The Cd concentrations significantly decreased with the larval age, whereas it was reverse for Cd contents. Cd concentrations in the larval faces and exuvia were significantly higher than those in control. Food digestion/consumption rate and conversion rate of the 3rd-5th instar larvae in the Cd-treatment group were significantly higher and lower than those in the control, respectively. Food utilization rate of the Cd-stressed 3rd-4th instar larvae were not significantly different from that of the control larvae with the same age. In contrast, the Cd-stressed 5th instar larvae showed a significantly lower food utilization rate than the control. These results indicated that gypsy moth larvae could remove some Cd from their bodies through effective excretion (e.g. feces and exuvia), with the mature larvae being more effective than the juveniles. The increases of larval body mass seemed to have a "dilution effect" on its Cd concentration. Under Cd stress, the gypsy moth larvae might maintain a certain level of food utilization rate for growth and development via a modulation of food consumption/conversion rates, but Cd-stress would still reduce the larval food utilization rate when it was beyond a certain threshold.

Effects of Offspring and Parental Inbreeding on Parent-Offspring Communication.

There is mounting evidence that inbreeding can have complex effects on social interactions among inbred and outbred individuals. Here, we investigate effects of offspring and maternal inbreeding on parent-offspring communication in the burying beetle Nicrophorus vespilloides. We find effects of the interaction between offspring and maternal inbreeding on maternal behavior. Outbred females provided more direct care toward inbred larvae, while inbred females provided similar levels of direct care toward inbred and outbred larvae. Furthermore, we find direct and indirect effects of offspring inbreeding on offspring begging and maternal behavior, respectively. Inbred larvae spent less time begging than outbred larvae, and (outbred) females provided more direct care and less indirect care toward inbred larvae. Finally, we find effects of the interaction between offspring and maternal inbreeding on larval body mass. Inbred and outbred offspring grew to a similar size when the female was outbred, while inbred offspring were of a smaller size when the female was inbred. Our results suggest that outbred females provided more care toward inbred offspring to compensate for their poor genetic quality. Our study advances our understanding of inbreeding by showing that inbreeding can have direct effects on the behavior of inbred individuals and indirect effects on the behavior of outbred individuals and that indirect effects on outbred individuals may in turn influence the fitness of inbred individuals.

Characterization of an Insecticidal Protein from Withania somnifera Against Lepidopteran and Hemipteran Pest.

Lectins are carbohydrate-binding proteins with wide array of functions including plant defense against pathogens and insect pests. In the present study, a putative mannose-binding lectin (WsMBP1) of 1124bp was isolated from leaves of Withania somnifera. The gene was expressed in E. coli, and the recombinant WsMBP1 with a predicted molecular weight of 31kDa was tested for its insecticidal properties against Hyblaea puera (Lepidoptera: Hyblaeidae) and Probergrothius sanguinolens (Hemiptera: Pyrrhocoridae). Delay in growth and metamorphosis, decreased larval body mass and increased mortality was recorded in recombinant WsMBP1-fed larvae. Histological studies on the midgut of lectin-treated insects showed disrupted and diffused secretory cells surrounding the gut lumen in larvae of H. puera and P. sanguinolens, implicating its role in disruption of the digestive process and nutrient assimilation in the studied insect pests. The present study indicates that WsMBP1 can act as a potential gene resource in future transformation programs for incorporating insect pest tolerance in susceptible plant genotypes.

Spatial variability in post-larval traits of Sicyopterus lagocephalus Pallas 1770 around Reunion Island

The spatial variability of S. lagocephalus post-larval traits, in February 2015, was investigated through comparison of pelagic larval duration (PLD), standard length (SL), body mass (BM) and condition factor among 6 rivers around Reunion Island. The variability of the same traits was also investigated within a recruitment event in another river, in January 2015. Our results showed homogeneity of the PLD both between sites during the recruitment of February 2015, and during the recruitment event of January 2015 at a given site. The other traits were different between the eastern and the western rivers. The post-larvae from the East were characterised by higher BM and condition factor whereas on the West they were longer. These differences can be explained by different environmental conditions experienced by larvae in the coastal oceanic water before they entered the river, but also by different migration routes during their marine dispersal. The coastal water on the eastern side, more turbid and probably trophically richer, could have induced a better growth of the post-larvae compared to those at the same age on the western side. A singularity was highlighted concerning the Marsouins River, located East of the island, where post-larvae were at a more advanced stage of their metamorphosis, characterised by both a smaller size and a lighter weight. This particularity was related to the location of the fishermen trapnet, positioned farther up river compared to all the other rivers, either West or East of the island.

Joint effects of brood size and resource availability on sibling competition

The evolution of sibling competition is promoted when the brood's demand for resources (brood size) exceeds the parents' supply of resources (resource availability). However, little is known about the joint effects of brood size and resource availability and whether these effects are independent of each other. We conducted a study on the burying beetle Nicrophorus vespilloides, in which we manipulated both brood size and resource availability. We manipulated brood size by providing parents with 5, 10 or 20 larvae and resource availability by providing parents with a 5, 10 or 20 g mouse carcass. We found that resource availability had positive effects on parental care, larval body mass and larval survival, while brood size had a negative effect on larval body mass and larval survival. There were positive effects of the interaction between brood size and resource availability on larval begging and larval body mass, suggesting that the slopes describing the effect of brood size on larval begging and larval body mass became less negative as carcass size increased. When we repeated the analysis using larval density (i.e. brood size/resource availability) as a proxy for the shortage of resources, there were negative effects on parental care, larval body mass and larval survival. Our results have important implications by showing that there were main effects of both brood size and resource availability, and that their effects were not always independent of each other. Thus, treating brood size and resource availability as independent factors is preferential to using offspring density.

Leptinotarsa cap ‘n’ collar isoform C/Kelch-like ECH associated protein 1 signaling is critical for the regulation of ecdysteroidogenesis in the larvae

Drosophila cap ‘n’ collar isoform C (CncC) and Kelch-like ECH associated protein 1 (Keap1) regulate metamorphosis by transcriptional control of a subset of genes involved in ecdysteroidogenesis, 20-hydroxyecdysone (20E) signaling, and juvenile hormone (JH) degradation. In the present paper, we found that prothoracicotropic hormone signal was required for the activation of LdCncC and LdKeap1 in Leptinotarsa decemlineata. Moreover, RNA interference of LdCncC or LdKeap1 in the fourth-instar larvae delayed development. As a result, the treated larvae obtained heavier larval and pupal fresh weights and had larger body sizes than the controls. Furthermore, knockdown of LdCncC or LdKeap1 significantly reduced the mRNA levels of four ecdysone biosynthetic genes (Ldspo, Ldphm, Lddib and Ldsad), lowered 20E titer and decreased the transcript levels of five 20E response genes (LdEcR, LdUSP, LdE75, LdHR3 and LdFTZ-F1). However, the expression of two JH epoxide hydrolase genes and JH contents were not affected in the LdCncC and LdKeap1 RNAi larvae. Dietary supplementation with 20E shortened the developmental period to normal length, rescued the larval and pupal body mass rises, and recovered or even overcompensated the expression levels of the five 20E response genes in either LdCncC or LdKeap1 RNAi hypomorphs. Therefore, LdCncC/LdKeap1 signaling regulates several ecdysteroidogenesis genes, and consequently 20E pulse, to modulate the onset of metamorphosis in L. decemlineata.

Feeding Preference and Performance ofHelicoverpa zea(Lepidoptera: Noctuidae) Larvae on Various Soybean Tissue Types

Abstract Helicoverpa zea Boddie (Lepidoptera: Noctuidae) feeding preference and performance on soybean tissue types is poorly understood. We assessed preference by looking at feeding behavior and resulting performance of 2nd and 4th instar H. zea larvae on leaves, flowers, and pods in no-choice and choice assays. Consumption indices were calculated and observed feeding behaviors were used to indicate preference; survival, growth rate, and larval body mass were recorded as measures of performance. Second instars performed better when fed leaf tissue than when fed other tissue types. In no-choice assays, 32% of 2nd instars that fed exclusively on newly emerging trifoliates reached the pupal stage, and 50% of those that fed exclusively on fully emerged leaf trifoliates survived to pupation. Early instar survival was poor (ranging from 0 to 3%) on all other tissue types, including flowers, stems, and pods. However, when given a choice of tissue types throughout their larval lifetime, 2nd instars preferred to ...

The effect of previous experience on trap construction and movement distance in a pit-building predator

Wormlion larvae are sit-and-wait predators that construct cone-shaped pits in sandy patches to capture prey. Wormlions select microhabitats that feature favorable conditions for pit construction, in a similar way to other trap-building predators, like spiders and antlions. We investigated whether wormlions exhibit an experience-based behavioral plasticity in their pit construction behavior. In a laboratory experiment, pit sizes and relocation distances were compared between larvae that experienced either a period of unfavorable conditions, i.e., surface obstacles, shallow or coarse sand, or a period of favorable conditions, i.e., clear, deep, and fine sand and were able to construct pits undisturbed. We expected that wormlions experiencing improving conditions would build larger pits than those experiencing deteriorating conditions. In addition, we expected that larvae experiencing unfavorable conditions would be less choosy in their new microhabitat and move over shorter distances. We observed a certain effect of recent experience on the trap-building behavior; however, it was not consistent among treatments. Additionally, we detected a correlation between larval body mass, relocation distance, and pit area. These findings might suggest that past experience does not influence wormlion foraging behavior in a simple manner but that different types of experience induce different behavioral responses.

Individual and mixture effects of selected pharmaceuticals on larval development of the estuarine shrimp Palaemon longirostris

Few ecotoxicological studies incorporate within the experimental design environmental variability and mixture effects when assessing the impact of pollutants on organisms. We have studied the combined effects of selected pharmaceutical compounds and environmental variability in terms of salinity and temperature on survival, development and body mass of larvae of the estuarine shrimp Palaemon longirostris. Drug residues found in coastal waters occur as mixture, and the evaluation of combined effects of simultaneously occurring compounds is indispensable for their environmental risk assessment. All larval stages of P. longirostris were exposed to the nonsteroidal anti-inflammatory drug (NSAID) diclofenac sodium (DS: 40 and 750μgL−1), the lipid regulator clofibric acid (CA: 17 and 361μgL−1) and the fungicide clotrimazole (CLZ: 0.14 and 4μgL−1). We observed no effect on larval survival of P. longirostris with the tested pharmaceuticals. However, and in contrast to previous studies on larvae of the related marine species Palaemon serratus, CA affected development through an increase in intermoult duration and reduced growth without affecting larval body mass. These developmental effects in P. longirostris larvae were similar to those observed in the mixture of DS and CA confirming the toxic effects of CA. In the case of CLZ, its effects were similar to those observed previously in P. serratus: high doses affected development altering intermoult duration, tended to reduce the number of larval instars and decreased significantly the growth rate. This study suggests that an inter-specific life histories approach should be taken into account to assess the effect of emergent compounds in coastal waters.

爵床的甲醇提取物对小菜蛾的生物活性

PDF HTML阅读 XML下载 导出引用 引用提醒 爵床的甲醇提取物对小菜蛾的生物活性作用 DOI: 10.5846/stxb201307261957 作者: 作者单位: 江西农业大学农学院 南昌,江西农业大学农学院 南昌,江西农业大学农学院 南昌,江西庐山植物园 庐山,江西庐山植物园 庐山 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31260437);江西省教育厅资助项目(GJJ11395) Bioactivity of methanol extracts from Justicia procumbens against Plutella xylostella Author: Affiliation: College of Agronomy, Jiangxi Agricultural University,College of Agronomy,Jiangxi Agricultural University,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探明爵床(Justicia procumbens)甲醇提取物对小菜蛾的生物活性,采用室内生测法测定了爵床甲醇提取物对小菜蛾的触杀、拒食、胃毒、生长发育抑制和产卵忌避作用。结果表明,爵床甲醇提取物对小菜蛾幼虫具有较强的触杀、拒食、胃毒和生长发育抑制活性,对小菜蛾成虫具有较强的产卵忌避活性。在触杀试验中,药后1、2 d和3 d爵床甲醇提取物对小菜蛾3龄幼虫的致死中浓度(LC50)分别为5.17、4.05和3.06 mg/mL;在拒食试验中,药后1 d和2 d提取物对3龄幼虫的选择性拒食中浓度(AFC50)分别为2.64和3.13 mg/mL,药后1 d和2 d提取物对3龄幼虫的非选择性拒食中浓度(AFC50)分别为3.70、4.54 mg/mL;在胃毒试验中,药后4、5、6 d和7 d提取物对3龄幼虫的致死中浓度(LC50)分别为8.13、3.65、2.88、2.23 mg/mL;在生长发育抑制试验中,药后1 d和2 d提取物对3龄幼虫的抑制中浓度(IC50)分别为2.02、1.40 mg/mL;在产卵忌避试验中,药后1、2 d和3 d提取物对小菜蛾成虫的选择性产卵忌避中浓度(AOC50)分别为2.61、3.66、4.58 mg/mL,药后1、2和3 d提取物对小菜蛾成虫的非选择性产卵忌避中浓度(AOC50)分别为3.19、4.52、5.65 mg/mL。由此证实,爵床提取物对小菜蛾具有显著的毒杀活性,具有开发为新型高效、低毒植物源农药的潜在价值。 Abstract:Plants are a treasure trove of bioactive compounds and research into the bioactivity of naturally occurring botanical compounds is an effective way to develop new pesticides. Pesticides can have many effects upon target organisms, including stomach poisoning, contact poisoning, systemic poisoning, fumigant poisoning, antifeeding and repelling activity, and growth regulation. Justicia procumbens is a traditional Chinese herbal medicine, and studies have shown that extracts from J. procumbens have insecticidal and antimicrobial activity. Plutella xylostella is an important agricultural pest of cruciferous vegetables in south China that, as it causes damage throughout the year, is responsible for huge economic losses. We used greenhouse bioassays to test the contact poisoning, antifeeding, stomach poisoning, growth regulating and oviposition-repelling effects of methanol extracts from J. procumbens against P. xylostella..Results showed that methanol extracts from J. procumbens had strong contact toxicity to P. xylostella, and that this activity was positively correlated to the concentration of the extracts. The LC50 values of methanol extracts against 3rd instar larvae of P. xylostella were 5.17, 4.05 and 3.06 mg/mL within 1, 2 and 3 d after treatment, respectively. Methanol extracts from J. procumbens had significant antifeedant activity against P. xylostella, whose antifeeding rate was positively correlated to the concentration of extracts. The effect of the extracts on selective antifeeding rates was stronger than on non-selective antifeeding rates, and the antifeedant effects were decreased noticeably over time: the AFC50 values were 2.64 and 3.13 mg/mL within 1 and 2 d after treatment under the selective conditions, and 3.70 and 4.54 mg/mL under the non-selective conditions. Methanol extracts from J. procumbens had strong stomach toxicity to P. xylostella, and the larval mortality was positively correlated with the concentration of the extracts and the time after treatment. In all treatments, no larvae died within 1 d after treatment. The mortality of larvae in the high concentration (32 mg/mL) treatment was 16.67% within 2 d after treatment and 46.67% within 3 d after treatment. The LC50 values of methanol extracts against the 3rd instar larvae of P. xylostella were 8.13, 3.65, 2.88 and 2.23 mg/mL within 4, 5, 6 and 7 d after treatment, respectively. Methanol extracts from J. procumbens had a significant dose-dependent inhibitory effect on the larval growth of P. xylostella. Larval body mass significantly decreased in all treatments of methanol extracts compared with control, and the magnitude of the decrease correlated with the extract concentration. The IC50 values of methanol extracts against the 3rd instar larvae of P. xylostella were 2.02 and 1.40 mg/mL within 1 and 2 d after treatment. Methanol extracts from J. procumbens had significant dose-dependent repelling effect on the adult oviposition of P. xylostella. There was a significant reduction in the number of eggs laid per female adult with an increasing concentration of extracts. At the same time, the oviposition repelling rate of extracts at all concentrations decreased with time, and the effect on selective repelling rates was stronger than on non-selective repelling rates. The AOC50 values were 2.61, 3.66 and 4.58 mg/mL within 1, 2 and 3 d after treatment under the selective conditions, respectively, and 3.19, 4.52 and 5.65 mg/mL under the non-selective conditions. The results suggested that methanol extracts from J. procumbens have significant insecticidal activity against P. xylostella, and have the potential to be developed into a new style of botanical pesticide with high efficacy and low non-target toxicity. 参考文献 相似文献 引证文献

The life cycle and production of three common stonefly species (Insecta, Plecoptera) in the Kedrovaya River (the south of Primorskii Territory)

The life cycles and production parameters of three common detritivorous stonefly species (Paracapnia khorensis, Amphinemura verrucosa, and Taenionema japonicum) from the Kedrovaya River at the Kedrovaya Pad Reserve (the south of Primorskii Territory, Russian Far East) were studied. Judging from the body size histograms, all these species are univoltine and have no winter diapause. Eggs develop directly; larval growth is slow, takes about 282–295 days, and proceeds even at low water temperatures in winter. The P. khorensis population is characterized by synchronous adult emergence and recruitment, as well as by slow continuous increase in larval linear size and body mass from June to March. Amphinemura verrucosa adults have a prolonged flight period from June to August, and their recruitment takes place for two months, till the end of November. Larvae grow during autumn and winter, but the most rapid growth is recorded in spring, when the water temperature rises, just before adult emergence in June and July. The development of T. japonicum is characterized by larval diapause in August and September when the water temperature is high. In October, larval growth is resumed and remains rapid through autumn and winter, up to adult emergence in May. The species studied had similar values of instantaneous growth rate (0.021–0.022 day−1), cohort production efficiency P/Bcohort (6.01–6.55), and annual efficiency of population production P/Bannual (7.78–8.11). More variable throughout the growing period was the mean biomass, and this accounted for the differences in secondary production values which ranged from 13.2 to 130.7 mg dry mass/m2.

Brood Guarding by an Adult Parasitoid Reduces Cannibalism of Parasitoid-Attacked Conspecifics by a Caterpillar Host

Adult female bethylid parasitoids (Hymenoptera: Bethylidae) commonly guard their offspring until they develop into later immature stages to protect them from competing parasitoids and predators. Another possible mortality factor is from caterpillar larvae that cannibalize parasitized conspecific larvae. This study determined the effect of brood guarding on the occurrence of host cannibalism by using a brood guarding bethylid parasitoid Goniozus legneri and a non-guarding braconid parasitoid Habrobracon gelechiae (Hymenoptera: Braconidae), both are gregarious ectoprasitoids that attack the obliquebanded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae). When a C. rosaceana larva parasitized by G. legneri was presented to a live conspecific larva, the frequency of cannibalism on the parasitized conspecific was lower in the presence than in the absence of a guarding female G. legneri. In contrast, when a C. rosaceana larva parasitized by H. gelechiae was presented to a live conspecific larva, the presence or absence of H. gelechiae did not affect cannibalism frequency. Cannibals did not gain a fitness advantage in terms of larval survival, developmental time, or body mass of developed pupae; therefore, cannibalism by the host larva may be a group defense against increased parasitism in subsequent population generations. We suggest that brood guarding by parasitoids can act as a broad defense strategy to protect offspring from the cannibalism of parasitized conspecifics by the host larvae.

Red foliage color reliably indicates low host quality and increased metabolic load for development of an herbivorous insect

Plant chemical defense and coevolved detoxification mechanisms in specialized herbivorous insects are fundamental in determining many insect–plant interactions. For example, Brassicale plants protect themselves from herbivory by producing glucosinolates, but these secondary metabolites are effectively detoxified by larvae of Pierid butterflies. Nevertheless, not all Brassicales are equally preferred by these specialist herbivores. Female Pieris butterflies avoid laying eggs on anthocyanin-rich red foliage, suggesting red color is a visual cue affecting oviposition behavior. In this study, we reared P. brassicae larvae on green and red cabbage leaves, to determine whether foliage color reliably indicates host plant quality. We did not find a difference in survival rates or maximal larval body mass in the two food treatments. However, larvae feeding on red cabbage leaves exhibited significantly lower growth rates and longer durations of larval development. Interestingly, this longer development was coupled with a higher consumption rate of dry food matter. The lower ratio of body mass gain to food consumption in larvae feeding on red cabbage leaves was coupled with significantly higher (ca. 10 %) larval metabolic rates. This suggests that development on red foliage may incur an increased metabolic load associated with detoxification of secondary plant metabolites. Energy and oxygen allocation to detoxification could come at the expense of growth and thus compromise larval fitness as a result of extended development. From an evolutionary perspective, red foliage color may serve as an honest defensive cue, as it reliably indicates the plant’s low quality as a substrate for larval development.

Protection of Neuronal Diversity at the Expense of Neuronal Numbers during Nutrient Restriction in the Drosophila Visual System

SummarySystemic signals provided by nutrients and hormones are known to coordinate the growth and proliferation of different organs during development. However, within the brain, it is unclear how these signals influence neural progenitor divisions and neuronal diversity. Here, in the Drosophila visual system, we identify two developmental phases with different sensitivities to dietary nutrients. During early larval stages, nutrients regulate the size of the neural progenitor pool via insulin/PI3K/TOR-dependent symmetric neuroepithelial divisions. During late larval stages, neural proliferation becomes insensitive to dietary nutrients, and the steroid hormone ecdysone acts on Delta/Notch signaling to promote the switch from symmetric mitoses to asymmetric neurogenic divisions. This mechanism accounts for why sustained undernourishment during visual system development restricts neuronal numbers while protecting neuronal diversity. These studies reveal an adaptive mechanism that helps to retain a functional visual system over a range of different brain sizes in the face of suboptimal nutrition.

The Sublethal Effects of Chlorantraniliprole on Helicoverpa armigera (Lepidoptera: Noctuidae)

Sublethal effects of chlorantraniliprole to Helicoverpa armigera (Hbner) larvae were evaluated through exposure of third instar larvae to the insecticide incorporated into an artificial diet. When larvae were fed on the insecticide-containing diet for 7 d, the LC10, LC20, LC40, and LC50 values were 3.790, 7.977, 21.577, and 33.121 μg active ingredient L−1, respectively. Chlorantraniliprole at sublethal concentrations significantly reduced the larval body mass, emergence ratio, adult longevity and egg hatching rate in both the parental and offspring generations. The pupation and copulation rate in the parental generation and the pupal mass in the offspring also strongly decreased. Reproduction was seriously disturbed in both the parental and offspring groups even when only one of the partners was exposed to chlorantraniliprole at larval stages. However, at the lowest concentration of exposure (LC10), offspring fecundity was strongly reduced only when both partners were exposed. The net reproductive rate (R0), intrinsic rate of increase (rm), and gross reproduction rate (GRR) at LC20, LC40 concentrations were significantly lower than that of the control. Post-exposure effects also included an extended larval developmental time and increased male proportion in both generations. The doubling time (Dt) at LC20, LC40 concentrations as well as gross reproduction rate (GRR) at LC10 concentration were also significantly increased. Chlorantraniliprole might have significant effects on H. armigera population dynamics even at sublethal concentrations on both parental and offspring generations.

Cloning eleven midgut trypsin cDNAs and evaluating the interaction of proteinase inhibitors with Cry1Ac against the tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae)

Midgut trypsins are associated with Bt protoxin activation and toxin degradation. Proteinase inhibitors have potential insecticidal toxicity against a wide range of insect species. This study was conducted to evaluate the interaction of proteinase inhibitors with Bt toxin and to examine midgut trypsin gene profile of Heliothis virescens. A sublethal dose (15ppb) of Cry1Ac, 0.75% soybean trypsin inhibitor, and 0.1% and 0.2% N-α-tosyl-L-lysine chloromethyl ketone significantly suppressed midgut proteinase activities, and resulted in reductions in larval and pupal size and mass. The treatment with inhibitor+Bt suppressed approximately 65% more larval body mass and 21% more enzymatic activities than the inhibitor-only or Bt-only. Eleven trypsin-like cDNAs were sequenced from the midgut of H. virescens. All trypsins contained three catalytic center residues (H73, D153, and S231), substrate specificity determinant residues (D225, G250, and G261), and six cysteines for disulfide bridges. These putative trypsins were separated into three distinct groups, indicating the diverse proteinases evolved in this polyphagous insect. These results indicated that the insecticidal activity of proteinase inhibitors may be used to enhance Bt toxicity and delay resistance development.

Post‐hatching parental care masks the effects of egg size on offspring fitness: a removal experiment on burying beetles

Parents can increase the fitness of their offspring by allocating nutrients to eggs and/or providing care for eggs and offspring. Although we have a good understanding of the adaptive significance of both egg size and parental care, remarkably little is known about the co-evolution of these two mechanisms for increasing offspring fitness. Here, we report a parental removal experiment on the burying beetle Nicrophorus vespilloides in which we test whether post-hatching parental care masks the effect of egg size on offspring fitness. As predicted, we found that the parent's presence or absence had a strong main effect on larval body mass, whereas there was no detectable effect of egg size. Furthermore, egg size had a strong and positive effect on offspring body mass in the parent's absence, whereas it had no effect on offspring body mass in the parent's presence. These results support the suggestion that the stronger effect of post-hatching parental care on offspring growth masks the weaker effect of egg size. We found no correlation between the number and size of eggs. However, there was a negative correlation between larval body mass and brood size in the parent's presence, but not in its absence. These findings suggest that the trade-off between number and size of offspring is shifted from the egg stage towards the end of the parental care period and that post-hatching parental care somehow moderates this trade-off.