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Third-instar Larvae (third-instar + larva)
Selected AbstractsBlockade of the central generator of locomotor rhythm by noncompetitive NMDA receptor antagonists in Drosophila larvaeDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2001Daniel Cattaert Abstract The noncompetitive antagonists of the vertebrate N -methyl- D -aspartate (NMDA) receptor dizocilpine (MK 801) and phencyclidine (PCP), delivered in food, were found to induce a marked and reversible inhibition of locomotor activity in Drosophilamelanogaster larvae. To determine the site of action of these antagonists, we used an in vitro preparation of the Drosophila third-instar larva, preserving the central nervous system and segmental nerves with their connections to muscle fibers of the body wall. Intracellular recordings were made from ventral muscle fibers 6 and 7 in the abdominal segments. In most larvae, long-lasting (>1 h) spontaneous rhythmic motor activities were recorded in the absence of pharmacological activation. After sectioning of the connections between the brain and abdominal ganglia, the rhythm disappeared, but it could be partially restored by perfusing the muscarinic agonist oxotremorine, indicating that the activity was generated in the ventral nerve cord. MK 801 and PCP rapidly and efficiently inhibited the locomotor rhythm in a dose-dependent manner, the rhythm being totally blocked in 2 min with doses over 0.1 mg/mL. In contrast, more hydrophilic competitive NMDA antagonists had no effect on the motor rhythm in this preparation. MK 801 did not affect neuromuscular glutamatergic transmission at similar doses, as demonstrated by monitoring the responses elicited by electrical stimulation of the motor nerve or pressure applied glutamate. The presence of oxotremorine did not prevent the blocking effect of MK 801. These results show that MK 801 and PCP specifically inhibit centrally generated rhythmic activity in Drosophila, and suggest a possible role for NMDA-like receptors in locomotor rhythm control in the insect CNS. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 58,73, 2001 [source] Remarks on the morphology and biology of Cleigastra apicalis (Meigen, 1826) (Diptera, Scathophagidae)ACTA ZOOLOGICA, Issue 4 2006Maria Grochowska Abstract The egg, second- and third-instar larvae and puparium of Cleigastra apicalis are described for the first time. All pre-imaginal stages are found on stems of the common reed affected by flies of the genera Lipara and Platycephala and the butterfly Arenostola phragmitidis. The larvae feed on dead plant and animal tissue and the excreta of other insects that live inside the stems of the common reed. Exceptionally they will scrape living plant tissue. The pupa is the overwintering stage. [source] RESIN COLLECTION AND SOCIAL IMMUNITY IN HONEY BEESEVOLUTION, Issue 11 2009Michael Simone Diverse animals have evolved an ability to collect antimicrobial compounds from the environment as a means of reducing infection risk. Honey bees battle an extensive assemblage of pathogens with both individual and "social" defenses. We determined if the collection of resins, complex plant secretions with diverse antimicrobial properties, acts as a colony-level immune defense by honey bees. Exposure to extracts from two sources of honey bee propolis (a mixture of resins and wax) led to a significantly lowered expression of two honey bee immune-related genes (hymenoptaecin and AmEater in Brazilian and Minnesota propolis, respectively) and to lowered bacterial loads in the Minnesota (MN) propolis treated colonies. Differences in immune expression were also found across age groups (third-instar larvae, 1-day-old and 7-day-old adults) irrespective of resin treatment. The finding that resins within the nest decrease investment in immune function of 7-day-old bees may have implications for colony health and productivity. This is the first direct evidence that the honey bee nest environment affects immune-gene expression. [source] Transcriptional signatures in response to wheat germ agglutinin and starvation in Drosophila melanogaster larval midgutINSECT MOLECULAR BIOLOGY, Issue 1 2009H.-M. Li Abstract One function of plant lectins such as wheat germ agglutinin is to serve as defences against herbivorous insects. The midgut is one critical site affected by dietary lectins. We observed marked cellular, structural and gene expression changes in the midguts of Drosophila melanogaster third instar larvae that were fed wheat germ agglutinin. Some of these changes were similar to those observed in the midguts of starved D. melanogaster. Dietary wheat germ agglutinin caused shortening, branching, swelling, distortion and in some cases disintegration of the midgut microvilli. Starvation was accompanied primarily by shortening of the microvilli. Microarray analyses revealed that dietary wheat germ agglutinin evoked differential expression of 61 transcripts; seven of these were also differentially expressed in starved D. melanogaster. The differentially transcribed gene clusters in wheat germ agglutinin-fed larvae were associated with (1) cytoskeleton organization; (2) digestive enzymes; (3) detoxification reactions; and (4) energy metabolism. Four possible transcription factor binding motifs were associated with the differentially expressed genes. One of these exhibited substantial similarity to MyoD, a transcription factor binding motif associated with cellular structures in mammals. These results are consistent with the hypothesis that wheat germ agglutinin caused a starvation-like effect and structural changes of midgut cells of D. melanogaster third-instar larvae. [source] Response of beech (Fagus sylvatica) to elevated CO2 and N: Influence on larval performance of the gypsy moth Lymantria dispar (Lep., Lymantriidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001M. W. Henn Two-year-old beech seedlings were kept from germination to bioassays with Lymantriadispar under the following conditions: ambient CO2/low N, elevated CO2/low N, ambient CO2/elevated N, and elevated CO2/elevated N. The effect of these growing conditions of the trees on the performance of the defoliator L. dispar was studied 2 years after initiating the tree cultivation. The developmental success of third-instar larvae of L. dispar was characterized by the weight gained, percentage of weight gain, relative growth rate (RGR), relative consumption rate (RCR), and efficiency of conversion of ingested food into body substance (ECI). Contrary to our expectations, additional N-fertilization did not increase and elevated CO2 did not delay larval growth rate. However, the environmental treatments of the beech seedlings were found to affect the larval performance. Larvae consumed significantly higher amounts of foliage (RCR) on beech trees under controlled conditions (ambient CO2 and low N) compared to those under elevated CO2 and enhanced N. The opposite was true for ECI. The lowest efficacy to convert consumed food to body substance was observed under control conditions and the highest when the larvae were kept on beech trees grown under elevated CO2 and additional N-fertilization. These opposite effects resulted in the weight gain-based parameters (absolute growth, percentage of growth, and RGR) of the gypsy moth larvae remaining unaffected. The results indicate that the gypsy moth larvae are able to change their ECI and RCR to obtain a specific growth rate. This is discussed as an adaptation to specific food qualities. [source] Influence of plant silicon and sugarcane cultivar on mandibular wear in the stalk borer Eldana saccharinaAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2009Olivia L. Kvedaras Abstract 1,Silicon can increase the resistance of plants to attack by herbivorous insects. The present study aimed to determine the effect of silicon and cultivar on mandibular wear in larvae of the sugarcane stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae). 2,Four sugarcane cultivars, resistant (N21, N33) and susceptible (N11, N26) to E. saccharina were grown in a pot trial in silicon deficient river sand, with (Si+) and without (Si,) calcium silicate. Individual third-instar larvae were confined on the sugarcane stalk at three known feeding sites (leaf bud, root band and internode) and left to feed for 21 days. 3,Eldana saccharina larval heads were mounted on stubs, with the mandibles oriented horizontally and photographed under a scanning electron microscope. Mandibular wear was measured from the digital images using a quantitative method. 4,Although there was a trend for increased wear in larvae that developed on Si+ cane, no significant effect of silicon, cultivar or site on mandibular wear of E. saccharina was shown. 5,This is the first study to accurately and quantitatively measure the mandibular wear of an insect fed on Si+ plants. [source] Mapping the peptide and protein immune response in the larvae of the fleshfly Sarcophaga bullataJOURNAL OF PEPTIDE SCIENCE, Issue 6 2008Alice Ciencialová Abstract We chose the larvae of fleshfly Sarcophaga bullata to map the peptide and protein immune response. The hemolymph of the third-instar larvae of S. bullata was used for isolation. The larvae were injected with bacterial suspension to induce an antimicrobial response. The hemolymph was separated into crude fractions, which were subdivided by RP-HPLC, gel electrophoresis, and free-flow electrophoresis. In several fractions, we determined significant antimicrobial activities against the pathogenic bacteria Escherichia coli, Staphylococcus aureus, or Pseudomonas aeruginosa. Among antimicrobially active compounds we identified dipeptide ,-alanyl- L -tyrosine, protein transferrin, and two variants of peptide sapecin. We also partially characterized two novel antimicrobially active polypeptides; odorant-binding protein 99b, and a peptide which remains unidentified. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source] Responses of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidaclopridPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 12 2009Lloyd M Dosdall Abstract BACKGROUND: The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new-generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment. RESULTS: Mean numbers of second- and third-instar larvae were significantly higher in plants seed-treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new-generation adults was reduced by 52 and 39% for plants seed-treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane. CONCLUSION: Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola. Copyright © 2009 Society of Chemical Industry [source] Impact of spray application methodology on the development of resistance to cypermethrin and spinosad by fall armyworm Spodoptera frugiperda (JE Smith)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2006Ali Al-Sarar Abstract The development of resistance to an insecticide under various types of application method has yet to be reported in the literature. Five fall armyworm Spodoptera armigera (JE Smith) colonies were reared in a chamber for ten generations before starting topical application bioassays. From each colony, 200,500 third,fourth-instar larvae were fed for 72 h on corn plants sprayed with cypermethrin or spinosad at minimum application rate (20 g ha,1) using a small droplet size nozzle XR8001VS (volume median diameter Dv0.5 = 163 µm) or a large droplet size nozzle XR8008VS (Dv0.5 = 519 µm). Surviving larvae were transferred to untreated corn leaves to complete their life cycle. Next-generation third-instar larvae of each colony were topically dosed with technical cypermethrin or spinosad at 1 µL per larva, and mortality was recorded 24 h post-treatment. The results indicated that cypermethrin demonstrated an insecticidal activity greater than that of spinosad, and the cypermethrin regression lines moved to the right faster than those for spinosad, indicating an increased tolerance of cypermethrin. Generally, larvae from all generations (F1,F7) under the XR8008VS treatments were less susceptible to cypermethrin and developed resistance faster and to higher levels than larvae from the XR8001VS treatments. The confidence limits (95%) of LD50 for all spinosad treatments indicated that there was no significant difference from the LD50 value of the susceptible reference strain. The results are a first indication that application technology/insecticide reaction may affect the rapidity of resistance development in certain pest/plant scenarios, but field studies are needed to confirm this conclusion. Copyright © 2006 Society of Chemical Industry [source] Hydrogen cyanide release during feeding of generalist and specialist lepidopteran larvae on a cyanogenic plant, Passiflora capsularisPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2006MIGUEL E. ALONSO AMELOT Abstract The hydrogen cyanide-based interaction of a strongly cyanogenic plant, Passiflora capsularis, and larvae of two insect herbivores, a generalist (Spodoptera frugiperda) and a specialist (Heliconius erato), is examined in terms of the combined kinetics of the feeding process and the simultaneous hydrogen cyanide (HCN) liberation, as compared with the natural kinetics of hydrogen cyanide evolution by plant-leaf tissue. There are marked differences in acceptance of P. capsularis by third-instar larvae of specialist and generalist species. The former, H. erato, display a parsimonious ingestion rate of 0.74 ± 0.15 mg (fresh weight) min,1 comprising 18% active feeding time, whereas S. frugiperda larvae show a more erratic and restrained feeding involving 4% of the time at 0.45 ± 0.14 mg min,1. These S. frugiperda larvae ingest 124.4 ± 8.3 mg (fw) of the non-cyanogeneic Spinacia oleracea leaves in 24 h compared with only 74.7 ± 20.1 mg of P. capsularis in the same period. The total hydrogen cyanide released naturally from wild specimens of P. capsularis plants is in the range 326,3901 ,g g,1. Hydrogen cyanide evolution from macerated P. capsularis leaves takes place along a hyperbolic function with time and initial velocities of cyanide evolution are a linear function of total hydrogen cyanide. When feeding on P. capsularis leaves, H. erato releases only a minor fraction relative to total hydrogen cyanide (0.09%) and to the anticipated cyanide from the initial velocity (7%). By contrast, S. frugiperda evokes 5.8-fold more than the anticipated hydrogen cyanide release from the plant. The findings are interpreted as diverging strategies by generalist and specialist insects in the utilization of hydrogen cyanide in cyanogenic plants. [source] Exceptional anoxia resistance in larval tiger beetle, Phaeoxantha klugii (Coleoptera: Cicindelidae)PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2003Matthias Zerm Abstract. The tiger beetle Phaeoxantha klugii inhabits Central Amazonian floodplains, where it survives the annual inundation period in the third-instar larval stage submerged in the soil at approximately 29 °C for up to 3.5 months. Because flooded soils quickly become anoxic, these larvae should be highly resistant to anoxia. The survival of adult and larval P. klugii was therefore tested during exposure to a pure nitrogen atmosphere in the laboratory at 29 °C. Adult beetles were not resistant (< 6 h). Survival of larvae decreased over time, maximum survival was 15 days, whereas time to 50% mortality was 5.7 days (95% confidence interval 3.8,7.9). Anoxia resistance was additionally tested in third-instar larvae submerged within sediment for 40 days before anoxia exposure in the laboratory. Anoxia resistance was greatly enhanced in these larvae, showing a survival rate of 50% after 26 days of anoxia exposure. It appears that the gradual flooding process and/or the submersion phase induced a physiological alteration, most probably a strong depression in metabolic rate, which requires some days for induction. The degree of anoxia resistance in larval P. klugii is remarkable among terrestrial arthropods worldwide, even more so considering the high ambient temperatures. The species is well-suited to serve as a model organism for studying the physiological mechanisms of anoxia and submersion resistance in terrestrial arthropods inhabiting tropical floodplains. [source] Susceptibility of four field populations of the diamondback moth Plutella xylostella L. (Lepidoptera: Yponomeutidae) to six insecticides in the Sydney region, New South Wales, AustraliaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008Vincent Y Eziah Abstract Concerns about the failure of insecticides to control the diamondback moth (DBM) Plutella xylostella in the Sydney region of New South Wales, Australia, necessitated the current investigation to establish the susceptibility of four field populations of the DBM to six insecticides. These include two each of organophosphates (OPs), and synthetic pyrethroid insecticides as well as two new products with different modes of action, spinosad and indoxacarb, currently recommended for DBM control in the region. Topical application of the insecticides to the third-instar larvae showed high resistance to pyrethroids (permethrin and esfenvalerate) of 35.0- to 490.0-fold. Resistance to the OPs (methamidophos and chlorpyrifos) and indoxacarb ranged from 12.1- to 36.2-fold and from 11.4- to 34.6-fold, respectively. However, the field populations were susceptible to spinosad (resistance factors only two- to threefold compared with the susceptible strain). A 2 h pre-treatment of the esfenvalerate-resistant strain with the synergists piperonyl butoxide and diethyl maleate increased the toxicity of esfenvalerate by 30.0- and 1.9-fold, respectively, suggesting the involvement of esterases and/or monooxygenases as the key mechanism(s) of insecticide resistance with glutathione S-transferases playing a minor role. [source] Temperature-dependent development and distribution in the soil profile of pupae of greyback canegrub Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae) in Queensland sugarcaneAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2007David P Logan Abstract, The temperature-dependent development rate of pupae of greyback canegrub, Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae), a major pest of sugarcane in central and northern Queensland, was determined under six constant temperature regimes: 18, 20, 23, 25, 27 and 30°C, and for four geographically separated populations. Development rate increased significantly with increasing temperature. Parameters of the linear regression equation did not differ among populations and common coefficients were calculated. Developmental zero, at and below which no development occurs, for pupae was 12.0°C and the thermal constant was 476 day-degrees (D°). Minimum and maximum periods for pupal development were 26 days at 30°C and 75 days at 18°C, respectively. The phenology of pupae was determined in soil-filled cubicles in a shade house and in the field at Ayr (19°35,S, 147°25,E), north Queensland, using D. albohirtum field-collected as late-stage third-instar larvae and kept in containers. Pupation of D. albohirtum began in late August or early September and eclosion was complete by mid- to late October. The phenology data were used to validate the development model. Eclosion was predicted by summing hourly fractions of day-degrees until 476 D° was reached and was close to actual eclosion. As temperature, and hence pupal development rate, varies with soil depth, the distribution of the third instars in pupal cells in the soil profile was determined in recently harvested fields of sugarcane in the Burdekin sugarcane district centred on Ayr. Numbers of late third instars in pupal cells peaked at 300,400 mm, with pupae found from 30 to 700 mm. Pupal development was simulated using hourly soil temperatures measured at depths of 200 and 400 mm at Ayr and at Sarina (21°22,S, 149°13,E). The pupal stage was predicted to take up to 2,10 days longer at 200 mm deep than at 400 mm depending on pupation site and date. When pupation was simulated in late August, as is likely in the field, pupal development at 400 mm deep took 48,56 days at Ayr and 58,62 days at Sarina. [source] Improved production of insecticidal proteins in Bacillus thuringiensis strains carrying an additional cry1C gene in its chromosomeBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2005Chaoyin Yue Abstract A cryIC gene, whose product is active against Spodoptera exigua, was introduced into wildtype Bacillus thuringiensis kurstaki strain YBT1520 using an integrative and thermosensitive vector, pBMB-FLCE, which was developed based on B. thuringiensis transposon Tn4430 harboring a tnpI-tnpA gene. With the mediation of TnpI-TnpA, the cry1C gene was integrated into the chromosome of the host strain. To prevent secondary integration, the integrative vector was eliminated by moving recombinant cultures to 46°C for generations. Two integrative recombinant B. thuringiensis strains BMB1520-E and BMB1520-F were obtained. In recombinant BMB1520-F, the cry1C gene was expressed stably at a significant level and did not reduce the expression of endogenous crystal protein genes. Bioassay results indicated that BMB1520-E and BMB1520-F showed a higher level of activity against S. exigua third-instar larvae than did their parent strains, in addition to the high toxicity to Plutella xylostella third-instar later larvae. © 2005 Wiley Periodicals, Inc. [source] Larvicidal Effects of Fungal Meroterpenoids in the Control of Aedes aegypti L., the Main Vector of Dengue and Yellow FeverCHEMISTRY & BIODIVERSITY, Issue 2 2008Regina Geris Abstract The mosquito Aedes aegypti is an increasing problem of public health, being the vector responsible for dengue and Yellow Fever in tropical and subtropical regions. The aim of this work was to determine the potential larvicidal activity of a series of meroterpenoids, compounds 1,7, previously obtained fungal secondary metabolites from Penicillium sp., against the third-instar larvae of A. aegypti. The lethal concentrations (LC50 and LC90) of 1,7 were evaluated 24,h after exposure. Dehydroaustin (4) was the most active meroterpenoid in the series, with an LC50 value of 2.9,ppm, making it an attractive natural insecticide. [source] | |||||||||||||