Larval Life Span Research Articles

Catalytic activities of wild-type C. elegans DAF-2 kinase and dauer-associated mutants.

DAF-2, the Caenorhabditis elegans insulin-like receptor homolog, regulates larval development, metabolism, stress response, and lifespan. The availability of numerous daf-2 mutant alleles has made it possible to elucidate the genetic mechanisms underlying these physiological processes. The DAF-2 pathway is significantly conserved with the human insulin/IGF-1 signaling pathway; it includes proteins homologous to human IRS, GRB-2, and PI3K, making it an important model to investigate human pathological conditions. We expressed and purified the kinase domain of wild-type DAF-2 to examine the catalytic activity and substrate specificity of the enzyme. Like the human insulin receptor kinase, DAF-2 kinase phosphorylates tyrosines within specific YxN or YxxM motifs, which are important for recruiting downstream effectors. DAF-2 kinase phosphorylated peptides derived from the YxxM and YxN motifs located in the C-terminal extension of the receptor tyrosine kinase, consistent with the idea that the DAF-2 receptor may possess independent signaling capacity. Unlike the human insulin or IGF-1 receptor kinases, DAF-2 kinase was poorly inhibited by the small-molecule inhibitor linsitinib. We also expressed and purified mutant kinases corresponding to daf-2 alleles that result in partial loss-of-function phenotypes in C. elegans. These mutations caused a complete loss of kinase function in vitro. Our biochemical investigations provide new insights into DAF-2 kinase function, and the approach should be useful for studying other mutations to shed light on DAF-2 signaling in C. elegans physiology.

Metabolic performance and feed efficiency of black soldier fly larvae.

The black soldier fly (BSF), Hermetia illucens, is used in entomoremediation processes because its larvae can use a variety of organic residues with high efficiency. However, feed efficiencies are variable and characterized by uncertainties. Recently developed growth and metabolic performance models have predicted across different studies that BSF larvae have used 53%-58% of the feed components they have assimilated, in terms of carbon equivalents, for growth throughout their lifetime when reared on chicken feed. This is termed their average net growth efficiency. The remainder of the carbon has been lost as CO2. However, mass balances made under similar conditions show that the weight gained by BSF larvae corresponds to only 14%-48% of the feed substrates removed, indicating substrate conversion efficiency. Both performance indicators show even greater variability if more feed substrates are considered. Feed assimilation and growth rates, costs of growth, maintenance, and larval lifespan have been shown to affect how efficiently BSF larvae convert feed into growth. The differences between average net growth efficiencies and substrate conversion efficiencies further indicate that feed is often not used optimally in entomoremediation processes and that the overall yield of such processes is not determined by larval performance alone but is the result of processes and interactions between larvae, substrates, microbes, and their physical environment. The purpose of this study is to illustrate how quantification of the metabolic performance of BSF larvae can help improve our understanding of the role of the larvae in entomoremediation processes.

Comparative biocidal effect of BioArt and Crataeva religiosa extracts against the groundnut seed pest Caryedon serratus (OL.) in Senegal

With a view to devising a strategy for protecting groundnut seeds against Caryedon serratus, we tested the biological impact of a product called BioArt made from the leaves of certain plants indigenous to Senegal (Crataeva religiosa, Calotropis procera and Azadirachta indica) and aqueous extracts of Crataeva religiosa on the external forms of C. serratus. The BioArt product caused the greatest mortality in adults. It induced maximum elimination (100%) of adults with the highest dose C1. Extracts of C. religiosa were less effective than BioArt on adults. They induced a maximum effect of 53.33% mortality with the highest dose C1. Females treated with BioArt laid fewer eggs than those treated with aqueous extracts of C. religiosa. With regard to the sex ratio of survivors, a comparative study of the different solutions showed that the BioArt product favoured females, while the C. religiosa extracts were equally distributed between males and females. The ovicidal activity showed almost equal embryonic and larval mortality and a slight difference in pupal mortality (32.41% with BioArt and 47.18% with C. religiosa). Monitoring of surviving eggs showed a lengthening or shortening of the various development times, with larval development, total development and life span being shorter with the BioArt product. The sex ratio was in favour of females for both products.

Cold-stored mulberry leaves affect antioxidant system and silk proteins of silkworm (Bombyx mori) larva.

Cold storage has been widely used to maintain the quality of vegetables, but whether eating cold-stored vegetables affects health remains unknown. This study used silkworms as an animal model to evaluate the effects of nutrient changes in cold-stored mulberry leaves (CSML) on health. Compared with fresh mulberry leaves (FML), CSML contained lower vitamin C, soluble sugars and proteins, and higher H2 O2 , suggesting decreased antioxidant ability and nutrition. The CSML did not obviously affect larval survival rate, body weight or dry matter rate, cocoon shape, weight and size, or final rates of cluster and cocooning relative to the FML, suggesting CSML did not alter overall growth and development. However, the CSML increased the initial rates of cluster and cocooning and upregulated BmRpd3, suggesting CSML shortened larval lifespan and enhanced senescence. CSML upregulated BmNOX4, downregulated BmCAT, BmSOD and BmGSH-Px and increased H2 O2 in silkworms, suggesting CSML caused oxidative stress. CSML upregulated ecdysone biosynthesis and inactivation genes and elevated ecdysone concentration in silkworms, suggesting that CSML affected hormone homeostasis. CSML upregulated apoptosis-related genes, downregulated sericin and silk fibroin genes and decreased sericin content rate in silkworms, suggesting oxidative stress and protein deficiency. Cold storage reduced nutrition and antioxidant capability of mulberry leaves. CSML did not influence growth and development of silkworm larva, but affected health by causing oxidative stress and reducing protein synthesis. The findings show that the ingredient changes in CSML had negative effects on health of silkworms. © 2023 Society of Chemical Industry.

The Drosophila melanogaster enzyme glycerol-3-phosphate dehydrogenase 1 is required for oogenesis, embryonic development, and amino acid homeostasis

As the fruit fly, Drosophila melanogaster, progresses from one life stage to the next, many of the enzymes that compose intermediary metabolism undergo substantial changes in both expression and activity. These predictable shifts in metabolic flux allow the fly meet stage-specific requirements for energy production and biosynthesis. In this regard, the enzyme glycerol-3-phosphate dehydrogenase 1 (GPDH1) has been the focus of biochemical genetics studies for several decades and, as a result, is one of the most well-characterized Drosophila enzymes. Among the findings of these earlier studies is that GPDH1 acts throughout the fly lifecycle to promote mitochondrial energy production and triglyceride accumulation while also serving a key role in maintaining redox balance. Here, we expand upon the known roles of GPDH1 during fly development by examining how depletion of both the maternal and zygotic pools of this enzyme influences development, metabolism, and viability. Our findings not only confirm previous observations that Gpdh1 mutants exhibit defects in larval development, lifespan, and fat storage but also reveal that GPDH1 serves essential roles in oogenesis and embryogenesis. Moreover, metabolomics analysis reveals that a Gpdh1 mutant stock maintained in a homozygous state exhibits larval metabolic defects that significantly differ from those observed in the F1 mutant generation. Overall, our findings highlight unappreciated roles for GPDH1 in early development and uncover previously undescribed metabolic adaptations that could allow flies to survive the loss of this key enzyme.

Pacific Lamprey Translocations to the Snake River Boost Abundance of All Life Stages

AbstractThe Pacific Lamprey Entosphenus tridentatus is an anadromous fish that has severely declined in the Snake River basin. In 2007, the Nez Perce Tribe initiated translocation of adults to this region from the main‐stem Columbia River and has continued the translocations to this day. These actions are aimed at restoring larval abundance along with holistic habitat improvements. We performed parentage and sibship analyses with 260 single‐nucleotide polymorphism loci to monitor productivity of translocated lamprey over a decade (2007–2018). These results provide the first direct evidence that translocations boosted larval abundance, increased juvenile production in the interior Columbia River (~3% in 2017 and 2018), and demonstrated successful migration to the Pacific Ocean. Per capita juvenile production from Snake River adult lamprey translocations out‐performed that of their volitionally migrating counterparts in the interior Columbia River, demonstrating that translocating adults to suitable habitats increased overall productivity. We projected that the translocations may eventually return enough adult offspring to the Columbia River to replace the annual take of adults for translocations, despite many adults likely returning to other basins. These translocations are also restoring Pacific Lamprey to historical areas where they had been nearly extirpated, which has impactful benefits both culturally and ecologically. Further, this study provided an unprecedented volume of data that has redefined key biological attributes, including timing of life stage transformation (average of 6.7‐year‐old juveniles), larval growth rates (~22 mm/year for the first 4 years), ocean duration (average of 5.1 years), dispersal (~3% of Snake River‐origin adults that return to the Columbia River will divert to the Willamette River), and life span (median age of postspawn adults was 12.9 years). We even quantified a new biological phenomenon of delayed spawning, which occurs at low rates (~9%) in nature. These data provide an opportunity to monitor ongoing translocation efforts and inform adaptive management to aid species recovery.

Potentiality of Novel Chitosan-O-Arginine as Insecticidal and Growth Inhibitory Compound against Diamondback Moth, Plutella xylostella L. on Cauliflower

Chitosan (Cs), a natural biodegradable polysaccharide polymer, prepared from sea waste of crustacean origin, has the potential for plant protection application. In the present study, a novel chitosan derivative, called Chitosan-O-Arginine, synthesized from crude chitosan, was evaluated for its chronic toxicity against second instar larvae of Plutella xylostella by leaf dip method. The results revealed the toxic potential of Chitosan-O-Arginine, which could inflict cent per cent mortality after four days of continuous feeding on the 1000 ppm treated leaf, and the larva could accomplish 0.12 mg weight (99.66% reduction) on the day before death. The next lower concentration (700 ppm) resulted in the maximum larval weight of 0.45 mg (93.71% reduction) after nine days of feeding and resulted in cent per cent mortality after the tenth day. While the untreated larva attained a maximum weight of 5.54 mg. All the larvae were pupated in the next lower concentration (500 ppm) and recorded minimum pupal (1.00 mg; 80% reduction) and adult (0.73 mg; 77.45% reduction) weight, whereas the untreated pupa and adult weighed the maximum of 5.00 mg and 3.20 mg. Considering the developmental period, there was no significant difference in the larval duration and adult life span. While there was an extension of the pupal period by one day at 500 ppm compared to untreated larva. The larval, pupal, and adult malformations were noticed in 300 and 100 ppm concentrations. These findings suggest that chitosan was potent in imposing chronic toxicity and growth inhibitory effect on P. xylostella larvae, and hence it can be recommended as an eco-friendly component in the Integrated Pest Management module.

Aging germline stem cells in C. elegans

Failure to maintain stem cells with age is associated with conditions such as tissue degeneration and increased susceptibility to tissue damage. We use the C. elegans germline stem cell system as a model to study stem cell aging. This system combines a well-established model for aging with an accessible stem cell system, providing a unique opportunity to understand how aging influences stem cell dynamics. The germline stem/progenitor pool in in C. elegans becomes depleted over time. At the cellular level, aging influences both the size of the stem cell pool and the proliferation rate of stem cells. The flux of differentiated cells also affects how aging impacts the pool. This depletion is partially alleviated in mutants with reduced insulin/IGF-like signaling via inhibition of the transcription factor DAF-16/FOXO. In this role, DAF-16 does not act in the germ line, and its anatomical requirements are different from its previously described roles in larval germline proliferation, dauer control, and lifespan regulation. We found that DAF-16/FOXO is required in certain somatic cells in the proximal part of the reproductive system to regulate the stem cell pool. We also find that the degree to which various age-defying perturbations affect lifespan does not correlate with their effect on germline stem cell maintenance. We are investigating additional aspects of aging germline stem cells using this system.

Azotobacter chroococcum inoculation can improve plant growth and resistance of maize to armyworm, Mythimna separata even under reduced nitrogen fertilizer application.

Nitrogen (N) is essential to crop yield improvement and it can change crops' ability to defend against herbivores. To maximize economic yield, a higher amount of N-fertilizer is often applied than the minimum required. Azotobacter is a good alternative to reduce N fertilizer application. In this study, we studied the yield and secondary defensive chemicals of maize, as well as the response of the key maize insect pest, Mythimna separata, as fed on maize plants inoculated with Azotobacter chroococcum and cultivated at different N fertilizer rates (i.e. the control rate of nitrogen fertilizer (CR), 80%CR and 60%CR) from 2018 to 2019. A. chroococcum inoculation just positively increased yield production of maize at 80%CR. Moreover, reduced N-fertilizer application and A. chroococcum inoculation had opposite impacts on the foliar contents of jasmonic acid (JA), isoleucine conjugate of JA (JA-Ile) and DIMBOA in maize, and they both negatively decreased the pupation rate and fecundity, and positively increased the eclosion rate and approximate digestibility (AD) of M. separata (P < 0.05). Furthermore, reduced N-fertilizer application negatively prolonged larval life-span, and decreased pupal weight, relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) of M. separata even A. chroococcum inoculation had positive effects on these indexes of M. separata (P < 0.05). These results help in understanding of the effects of low-level N-fertilizer and A. chroococcum inoculation on maize production and maize resistance to insects. This will be conducive to the integrated control of agricultural pests. © 2020 Society of Chemical Industry.

Laboratory testing of low concentration (

IntroductionLarvicide application in ovitrap is one of the currently available methods used in mosquito eradication campaign. We previously reported that copper in liquid form is a promising candidate due to its potent larvicide properties in a laboratory setting and in the field. In the field study, several larvae survived in outdoor ovitrap due to the dilution of copper concentration by rainwater. The surviving larvae were smaller and less motile. This led our interest to study the effect of a sub-lethal dose of copper in ovitrap on mosquito larval development, pupation time and lifespan in the adult stage.MethodsFirst instar larvae of Aedes albopictus, Anopheles stephensi, and Culex pipiens were put in water containing 0.15 ppm, 0.30 ppm, and 0.60 ppm of copper. The surviving larvae, the emerging pupae, and adult mosquitoes were observed and counted every 24-hour and statistically analyzed by t-test or Mann-Whitney U test. Inter-species difference in response to different concentration of copper were also analyzed.ResultsCopper showed a potent larvicide effect at 0.60 ppm concentration. Prolonged pupation time and a lower number of adult mosquitoes were observed at 0.15 ppm concentration. Copper exposure did not affect adult mosquitoes’ lifespan. Culex pipiens was the most susceptible species to copper exposure.ConclusionThis study demonstrates the efficacy of copper at <1 ppm to kill mosquito larvae and to prolong pupation and adult emergence time. Utilization of copper at a low concentration is cost-efficient in the public health setting and remains an open option as an environmentally safe vector control strategy.

Responses of multiple generations of Spodoptera littoralis feeding on gossypol

One of our objectives in this investigation is to determine responses of S. littoralis through different developmental stages and generations to secondary metabolic compound presumably gossypol. Gossypol did not significantly show antifeedant except with high concentration (1.7% gossypol in the diet) that gave 10.6, 21.9, and 46.8% for three generations, respectively. Significantly longer larval life-spans were observed in S. littoralis on a high concentration of gossypol compared with those fed on low concentrations. The larval and pupal weight of the third generation was significantly lower than that of the previous two generations as latent effects on survived larvae significantly lower fecundity was found in the second and third generations. A significantly lower relative growth rate was observed in the three successive generations. Generally, the efficiency of gossypol was significantly higher in the second and third generations. Gossypol significantly affected growth and development, suggesting that diet-gossypol efficiency was different based on concentration and generation. This study will shed some light on the possibility of controlling S. littoralis by gossypol through the sequence of alternative spraying programs.

Evidence for family-level variation of phenotypic traits in response to temperature of Brazilian Nyssorhynchus darlingi

BackgroundNyssorhynchus darlingi (also known as Anopheles darlingi) is the primary malaria vector in the Amazon River Basin. In Brazil, analysis of single nucleotide polymorphisms (SNPs) previously detected three major population clusters, and a common garden experiment in a laboratory setting revealed significant population variation in life history traits. Increasing temperatures and local level variation can affect life history traits, i.e. adult longevity, that alter vectorial capacity with implications for malaria transmission in Ny. darlingi.MethodsWe investigated the population structure of Ny. darlingi from 7 localities across Brazil utilizing SNPs and compared them to a comprehensive Ny. darlingi catalog. To test the effects of local level variation on life history traits, we reared F1 progeny from the 7 localities at three constant temperatures (20, 24 and 28 °C), measuring key life history traits (larval development, food-starved adult lifespan, adult size and daily survival).ResultsUsing nextRAD genotyping-by-sequencing, 93 of the field-collected Ny. darlingi were genotyped at 33,759 loci. Results revealed three populations (K = 3), congruent with major biomes (Amazonia, Cerrado and Mata Atlântica), with greater FST values between biomes than within. In the life history experiments, increasing temperature reduced larval development time, adult lifespan, and wing length in all localities. The variation of family responses for all traits within four localities of the Amazonia biome was significant (ANOVA, P < 0.05). Individual families within localities revealed a range of responses as temperature increased, for larval development, adult lifespan, wing length and survival time.ConclusionsSNP analysis of several Brazilian localities provided results in support of a previous study wherein populations of Ny. darlingi were clustered by three major Brazilian biomes. Our laboratory results of temperature effects demonstrated that population variation in life history traits of Ny. darlingi exists at the local level, supporting previous research demonstrating the high plasticity of this species. Understanding this plasticity and inherent variation between families of Ny. darlingi at the local level should be considered when deploying intervention strategies and may improve the likelihood of successful malaria elimination in South America.

Assessment of the Toxic Effects of Chitosan-Coated Magnetite Nanoparticles on Drosophila melanogaster

Nanoparticles are a cause for concern because of their potential toxic effects on human health and the environment. The aim of this study was to assess the toxic effect of chitosan-coated magnetite nanoparticles (11.00±4.7 nm) on Drosophila melanogaster through the observation of hemolymph composition, DNA damage, larval survival and lifespan of flies. Chitosan-coated magnetite nanoparticles were synthesized by co-precipitation method. Drosophila larvaes and adults were exposed to 500 and 1000 ppm nanoparticles solution. After exposure, each type of larval hemocytes was recognized. Comet assay was performed to detect the DNA damage in the hemocytes. Also, the larval survival and lifespan of exposed flies were observed. Our results showed the toxic effect of the chitosan-coated magnetite nanoparticles through the increment of hemocytes, the emergence of lamellocytes, the presence of apoptotic hemocytes and the DNA damage detected by comet assay. In addition, nanoparticles produce decreasing of larval survival and shortening of the mean and maximum lifespan. The toxic effect the chitosan-coated magnetite nanoparticles is directly associated with 1000 ppm. No DNA damage was observed at 500 ppm.

Arbuscular mycorrhizal fungi alter the food utilization, growth, development and reproduction of armyworm (Mythimna separata) fed on Bacillus thuringiensis maize.

BackgroundThe cultivation of Bt maize (maize genetically modified with Bacillus thuringiensis) continues to expand globally. Arbuscular mycorrhizal fungi (AMF), an important kind of microorganism closely related to soil fertility and plant nutrition, may influence the ecological risk of target lepidopteran pests in Bt crops.MethodsIn this study, transgenic Bt maize (Line IE09S034 with Cry1Ie vs. its parental line of non-Bt maize cv. Xianyu335) was inoculated with a species of AMF, Glomus caledonium (GC). Its effects on the food utilization, reproduction and development of armyworm, Mythimna separata, were studied in a potted experiment from 2017 to 2018.ResultsGC inoculation increased the AMF colonization of both modified and non-modified maize, and also increased the grain weight per plant and 1,000-grain weight of modified and non-modified maize. However, the cultivation of Bt maize did not significantly affect the AMF colonization. The feeding of M. separata with Bt maize resulted in a notable decrease in RCR (relative consumption rate), RGR (relative growth rate), AD (approximate digestibility), ECD (efficiency of conversion of digested food) and ECI (efficiency of conversion of ingested food) parameters in comparison to those observed in larvae fed with non-Bt maize in 2017 and 2018, regardless of GC inoculation. Furthermore, remarkable prolongation of larval life span and decreases in the rate of pupation, weight of pupa, rate of eclosion, fecundity and adult longevity of M. separata were observed in the Bt treatment regardless of GC inoculation during the two-year experiment. Also, when M. separata was fed with Bt maize, a significant prolongation of larval life and significant decreases in the pupal weight, fecundity and adult longevity of M. separata were observed when inoculated with GC. However, it was just the opposite for larvae fed with non-Bt maize that was inoculated with GC. The increased percentage of larval life-span, the decreased percentages of the food utilization, and the other indexes of reproduction, growth, and development of M. separata fed on Bt maize relative to non-Bt maize were all visibly lower when under GC inoculation in contrast to the CK.DiscussionIt is presumed that Bt maize has a marked adverse impact on M. separata development, reproduction and feeding, especially when in combination with the GC inoculation. Additionally, GC inoculation favors the effectiveness of Bt maize against M. separata larvae by reducing their food utilization ability, which negatively affects the development and reproduction of the armyworm. Thus, Bt maize inoculated with AMF (here, GC) can reduce the severe threats arising of armyworms, and hence the AMF inoculation may play an important ecological functions in the field of Bt maize ecosystem, with potentially high control efficiency for the target lepidopteran pests.

Impacts of Bt maize inoculated with rhizobacteria on development and food utilization of Mythimna separata

AbstractThe current trend of increasing proportion of cultivation of transgenic Bt crops is pushing towards dramatic destabilization of the agroecosystem, thus raising severe concerns about the sustainability of transgenic Bt crops as an effective management tool for the control of target insect pests in the future. Rhizobacteria is the key biological regulator to ameliorate soil‐nitrogen utilization efficiency of crop plants, especially transgenic Bt crops. A laboratory study quantified the impacts of transgenic Bt maize (Line IE09S034 with Cry1Ie vs. non‐Bt maize cv. Xianyu335) inoculated with Azospirillum brasilense (AB) and Azotobacter chroococcum (AC) on the growth, development and food utilization of a target lepidopteran insect, Mythimna separata. The results showed that the inoculation of rhizobacteria significantly prolonged the larval lifespan and pupal duration, increased RCR and AD, reduced pupal weight, pupation rate, fecundity, RGR, ECD and ECI, and shortened adult longevity of M. separata fed on transgenic Bt maize, while exact opposite trends were found in these measured indexes of growth, development and food utilization for M. separata fed on non‐Bt maize inoculated with AB and AC compared with the buffer control in both years. Thus, the results clearly depicted that the inoculation of rhizobacteria had opposite influences on the growth, development and food utilization of M. separata fed on transgenic Bt maize. Presumably, rhizobacteria inoculation can be used to stimulate plant–soil‐nitrogen uptake and promote plant growth for transgenic Bt maize and non‐Bt maize, simultaneously increasing Bt toxin production and enhancing resistance efficiency against target lepidopteran pests for transgenic Bt maize.

Microorganism-Based Larval Diets Affect Mosquito Development, Size and Nutritional Reserves in the Yellow Fever Mosquito Aedes aegypti (Diptera: Culicidae).

BackgroundMosquito larvae feed on organic detritus from the environment, particularly microorganisms comprising bacteria, protozoa, and algae as well as crustaceans, plant debris, and insect exuviae. Little attention has been paid to nutritional studies in Aedes aegypti larvae.ObjectivesWe investigated the effects of yeast, bacteria and microalgae diets on larval development, pupation time, adult size, emergence, survivorship, lifespan, and wing morphology.Materials and MethodsMicroorganisms (or Tetramin® as control) were offered as the only source of food to recently hatched first instar larvae and their development was followed until the adult stage. Protein, carbohydrate, glycogen, and lipid were analyzed in single larvae to correlate energetic reserve accumulation by larva with the developmental rates and nutritional content observed. FITC-labeled microorganisms were offered to fourth instar larvae, and its ingestion was recorded by fluorescence microscopy and quantitation.Results and DiscussionImmature stages developed in all diets, however, larvae fed with bacteria and microalgae showed a severe delay in development rates, pupation time, adult emergence and low survivorship. Adult males emerged earlier as expected and had longer survival than females. Diets with better nutritional quality resulted in adults with bigger wings. Asaia sp. and Escherichia coli resulted in better nutrition and developmental parameters and seemed to be the best bacterial candidates to future studies using symbiont-based control. The diet quality was measured and presented different protein and carbohydrate amounts. Bacteria had the lowest protein and carbohydrate rates, yeasts had the highest carbohydrate amount and microalgae showed the highest protein content. Larvae fed with microalgae seem not to be able to process and store these diets properly. Larvae were shown to be able to process yeast cells and store their energetic components efficiently.ConclusionTogether, our results point that Ae. aegypti larvae show high plasticity to feed, being able to develop under different microorganism-based diets. The important role of Ae. aegypti in the spread of infectious diseases requires further biological studies in order to understand the vector physiology and thus to manage the larval natural breeding sites aiming a better mosquito control.

Experimental N and P additions alter stream macroinvertebrate community composition via taxon‐level responses to shifts in detrital resource stoichiometry

Abstract Increases in nitrogen (N) and phosphorus (P) availability are changing animal communities, partly by altering stoichiometric imbalances between consumers and their food. Testing relationships between resource stoichiometry and consumer assemblage structure requires ecosystem‐level manipulations that have been lacking to date. We analysed patterns of macroinvertebrate community composition in five detritus‐based headwater streams subject to experimental whole‐stream N and P additions that spanned a steep gradient in dissolved N:P ratio (2:1, 8:1, 16:1, 32:1, 128:1) over 2 years, following a 1‐year pre‐treatment period. We predicted that shifts in leaf litter stoichiometry would drive overall patterns of community composition via greater responses of shredders to enrichment than other taxa, as shredders dominate primary consumer biomass and experience larger consumer–resource elemental imbalances than other functional groups in stream ecosystems. Specifically, we expected litter C:P to be a significant predictor of shredder biomass given the greater relative imbalances between shredder and litter C:P than C:N. Finally, we tested whether shredder responses to enrichment were related to other taxon‐level traits, including body size and stoichiometry, larval life span and growth rate. Whole‐community composition shifted similarly across the five streams after enrichment, largely driven by increased shredder and predator biomass. These shifts were limited to the autumn/winter seasons and related to decreased leaf litter C:P, highlighting important links between the quality of seasonal litter subsidies and community phenology. Among 10 taxa that drove structural shifts, two declined while other taxa from the same functional/taxonomic groups responded positively, suggesting that specific life‐history traits may determine sensitivity to enrichment. Increases in total shredder biomass, and in biomass of several common shredders, were associated with lower litter C:P. Body C:P did not predict shredder response to enrichment. However, weak negative relationships between shredder response and body size, and larval life span, suggest that small‐bodied and short‐lived taxa may be more responsive to shifting resource stoichiometry. Moderate anthropogenic increases in N and P availability affect resource stoichiometry and can alter animal communities, influencing additional food web and ecosystem properties. We provide support for ecological stoichiometry as a framework for predicting such outcomes based on changes in the elemental composition of resource pools. A plain language summary is available for this article.

Biological parameters of two syrphid fly species Ischiodon scutellaris (Fabricius) and Episyrphus balteatus (DeGeer) and their predatory potential on wheat aphid Schizaphis graminum (Rondani) at different temperatures

Syrphid flies, Ischiodon scutellaris (Fabricius) and Episyrphus balteatus (DeGeer), are among the most common aphidophagous species in wheat growing areas of Punjab, Pakistan. Exploit predatory species efficiently in any biological control program requires an in-depth understanding of predator and prey interactions. The present study was conducted aiming to explore and compare the predatory potential of these predatory species against the wheat aphid, Schizaphis graminum (Rondani) along with their relative fitness at different temperatures in terms of duration of lifecycle stages under laboratory conditions. The shortest egg and pupal durations were observed at 33 °C, followed by 27 and 23 °C. Females of both species had longer life span (20.4 and 22.4 days) compared to the respective males (17.2 and 16.2 days). The pupal stage for I. scutellaris was significantly shorter than for E. balteatus at different temperatures; but statistically insignificant differences were found for any other life stage. The larvae of I. scutellaris consumed significantly more aphids (438.16) than E. balteatus (398.37) during their larval life span, and this difference was significant during the 1st and 3rd instars. However, the average daily prey intake of both species was found similar until the 10th day after hatching, and thereafter, I. scutellaris consumed significantly higher numbers of aphids/day. Obtained results may offer a baseline data for future conservation studies on biological control of aphids.

Influence of elevated CO2 on development and food utilization of armyworm Mythimna separata fed on transgenic Bt maize infected by nitrogen-fixing bacteria.

BackgroundBt crops will face a new ecological risk of reduced effectiveness against target-insect pests owing to the general decrease in exogenous-toxin content in Bt crops grown under elevated carbon dioxide (CO2). The method chosen to deal with this issue may affect the sustainability of transgenic crops as an effective pest management tool, especially under future atmospheric CO2 level raising.MethodsIn this study, rhizobacterias, as being one potential biological regulator to enhance nitrogen utilization efficiency of crops, was selected and the effects of Bt maize (Line IE09S034 with Cry1Ie vs. its parental line of non-Bt maize Xianyu 335) infected by Azospirillum brasilense (AB) and Azotobacter chroococcum (AC) on the development and food utilization of the target Mythimna separate under ambient and double-ambient CO2 in open-top chambers from 2016 to 2017.ResultsThe results indicated that rhizobacteria infection significantly increased the larval life-span, pupal duration, relative consumption rate and approximate digestibility of M. separata, and significantly decreased the pupation rate, pupal weight, adult longevity, fecundity, relative growth rate, efficiency of conversion of digested food and efficiency of conversion of ingested food of M. separata fed on Bt maize, while here were opposite trends in development and food utilization of M. separata fed on non-Bt maize infected with AB and AC compared with the control buffer in 2016 and 2017 regardless of CO2 level.DiscussionSimultaneously, elevated CO2 and Bt maize both had negative influence on the development and food utilization of M. separata. Presumably, CO2 concentration arising in future significantly can increase their intake of food and harm to maize crop; however, Bt maize infected with rhizobacterias can reduce the field hazards from M. separata and the application of rhizobacteria infection can enhance the resistance of Bt maize against target lepidoptera pests especially under elevated CO2.

Effects of Elevated CO2 on Plant Chemistry, Growth, Yield of Resistant Soybean, and Feeding of a Target Lepidoptera Pest, Spodoptera litura (Lepidoptera: Noctuidae).

Atmospheric CO2 level arising is an indisputable fact in the future climate change, as predicted, it could influence crops and their herbivorous insect pests. The growth and development, reproduction, and consumption of Spodoptera litura (F.) (Lepidoptera: Noctuidae) fed on resistant (cv. Lamar) and susceptible (cv. JLNMH) soybean grown under elevated (732.1 ± 9.99 μl/liter) and ambient (373.6 ± 9.21 μl/liter) CO2 were examined in open-top chambers from 2013 to 2015. Elevated CO2 promoted the above- and belowground-biomass accumulation and increased the root/shoot ratio of two soybean cultivars, and increased the seeds' yield for Lamar. Moreover, elevated CO2 significantly reduced the larval and pupal weight, prolonged the larval and pupal life span, and increased the feeding amount and excretion amount of two soybean cultivars. Significantly lower foliar nitrogen content and higher foliar sugar content and C/N ratio were observed in the sampled foliage of resistant and susceptible soybean cultivars grown under elevated CO2, which brought negative effects on the growth of S. litura, with the increment of foliar sugar content and C/N ratio were greater in the resistant soybean in contrast to the susceptible soybean. Furthermore, the increment of larval consumption was less than 50%, and the larval life span was prolonged more obvious of the larvae fed on resistant soybean compared with susceptible soybean under elevated CO2. It speculated that the future climatic change of atmospheric CO2 level arising would likely cause the increase of the soybean yield and the intake of S. litura, but the resistant soybean would improve the resistance of the target Lepidoptera pest, S. litura.