Incidence of natural enemies of the Colorado potato beetle,Leptinotarsa decemlineata [Coleoptera: Chrysomelidae] on a native host in Mexico

In central Mexico, the center of origin forLeptinotarsa decemlineata (Say) and its principal host plants,L. decemlineata is associated with a diverse complex of natural enemies. Observations during 2 years in Morelos, Mexico revealed 4 species of asopine pentatomids, 7 species of foliar searching carabids, and 2 coccinellids among the predators ofL. decemlineata. Parasitoids include 3 species of tachinids andEdovum puttleri Grissel, an eulophid egg parasitoid. These natural enemies include several predators that have not previously been reported attackingL. decemlineata. University of Maine Agriculture Experiment Station No. 1553     

Abdominal movements, heartbeats and gas exchange in pupae of the Colorado potato beetle, Leptinotarsa decemlineata

The rhythms of abdominal movements, heartbeats and gas exchange in the pupae of Leptiontarsa decemlineata (Say) were recorded simultaneously using an electrolytic respirometer and infrared gas analyser, both combined with contact thermography. Abdominal pulsations and heartbeat occurred periodically with little variance among individuals. The abdominal pulsations and heartbeat pauses varied individually within large limits, with the frequency of abdominal pulsations being six to seven times lower than that of the heart pulses. A proportion of the pupae (20%) showed discontinuous gas exchange with large, actively ventilated CO₂ bursts, whereas others (≈ 25%) exhibited continuous regular microcycles (flutter) with abrupt intake of air into the tracheae before discrete microbursts of carbon dioxide. The abdominal pulsations exerted only a minor influence on ventilation during the microcycles. More than 90% of the bursts of abdominal movement coincided with a series of forward directed heartbeats, but interspersed between the bouts of abdominal movement commonly two to three heartbeat pulses were observed that were not associated with abdominal movements. A period of abdominal movement associated with a heartbeat pulse was commonly initiated by one or two vigorous strokes of abdominal rotation.     

Effect of photoperiod and allatectomy on reproduction and (second) diapause induction in post-diapause adult females of the Colorado potato beetle,Leptinotarsa decemlineata Say

Summary

The effect of photoperiod and allatectomy on the rates of oviposition and juvenile hormone (JH) synthesis was studied in female beetles after the break of adult diapause. The results indicate that after diapause, photoperiod has no effect on oviposition rates. However, the photoperiodic effect on diapause induction is restored within a few days after the break of the first diapause. Allatectomy performed within one day after diapause did not induce a second diapause, whereas about 40% of the beetles allatectomized after 3 or more days responded by entering a second diapause. Oogenesis in the operated animals was never completely prevented under long and short day conditions. These preliminary results suggest a change in the sensitivity of post-diapause beetles to photoperiodic and endocrine manipulation as compared with pre-diapause insects.     

Contribution of habitat type to residency and dispersal choices by overwintered and summer adult Colorado potato beetles

The walking and flight dispersal of marked overwintered and summer Colorado potato beetles (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), released in field box‐plots was monitored simultaneously in six habitats over a period of 4 days. The emigration out of plots by walking beetles was calculated from the catch in linear pitfall traps completely surrounding each box‐plot and emigration flight was estimated from the number of beetles missing from the plot or captured by the trap. Overwintered beetles dispersed sooner after release than summer beetles. Overall, the mean number of beetles retained by the habitat was significantly higher in the host habitat (potato) than in any non‐host habitat tested (soybean, pasture, bare ground, water, woodland). Unexpectedly, there was no or little difference in overall beetle retention between non‐host habitats except for higher retention in the water habitat. No difference in the ratio of flight over walking could be detected by the study between overwintered and summer CPB except in the water and woodland habitats. Twenty‐four hours after release, the highest ratios were obtained in the water and woodland habitats and the lowest in the bare‐ground habitat, but ratios were similar for all habitats, except water, after 96 h. As a population, under these experimental conditions, 96 h after release, it seems that CPB displayed a slight preference for flight over walking, with walking as a default mode. A fed and starved pre‐release treatment had no effect on dispersal rates or mode of dispersal. Essentially, our results showed that over a 96‐h period, northeastern North American CPB emigrated at similar rates from the various non‐host habitats encountered, except for water, using walking as much as flight. The host habitat retained CPB significantly longer than non‐host habitats but with a mode of dispersal ratio similar to that in non‐host habitats. The impact on dispersal of the various habitats encountered by CPB in the agro‐ecosystem was less important than expected suggesting that the interaction of environmental parameters is likely to have the most significant impact in determining dispersal rates and dispersal modes.     

马铃薯甲虫结节性硬化复合物基因LdTSC1和LdTSC2基因的克隆及功能分析

【目的】通过RNAi技术明确马铃薯甲虫TOR上游的关键信号集成节点及类胰岛素信号通道下游基因结节性硬化复合物TSC1和TSC2的功能。旨在为探明马铃薯甲虫类胰岛素信号转导提供更多理论支持。【方法】在NCBI(美国国家生物技术信息中心)获取马铃薯甲虫LdTSC1/2序列,分别利用多重序列比对和系统发育分析确定该基因的完整性和系统发育关系;采用喂食幼虫dsRNA的方法,观察该基因的调低对马铃薯甲虫幼虫生长发育、糖脂代谢的影响。【结果】克隆得到马铃薯甲虫TSC1编码蛋白的氨基酸序列与鞘翅目白蜡窄吉丁直系同源蛋白的氨基酸序列的自展一致度为100%,聚为一支;TSC2编码蛋白的氨基酸序列与鞘翅目白蜡窄吉丁和赤拟谷盗的同源蛋白氨基酸序列的自展一致度为100%,聚为一支。通过分别喂食2龄幼虫LdTSC1/2的dsRNA能有效降低靶标基因的表达量,幼虫出现体重减轻,化蛹率和羽化率显著下降,葡萄糖的吸收转化效率降低,海藻糖含量升高和甘油三酯均减少。【结论】下调2龄幼虫LdTSC1/2的表达量,导致试虫出现抑制了糖脂代谢、脂肪体减少、体重减轻以及发育延迟;结果表明LdTSC1/2调控了马铃薯甲虫幼虫的糖脂代谢过程,显著影响幼虫化蛹和蜕皮过程。     

cDNA cloning,expression, and enzymatic activity of a novel endogenous cellulase from the beetle Batocera horsfieldi

In this study, we report a novel cellulase [β-1,4-endoglucanase (EGase), EC 3.2.1.4] cDNA (Bh-EGase II) belonging to the glycoside hydrolase family (GHF) 45 from the beetle Batocera horsfieldi. The Bh-EGase II gene spans 720 bp and consists of a single exon coding for 239 amino acid residues. Bh-EGase II showed 93.72% protein sequence identity to Ag-EGase II from the beetle Apriona germari. The GHF 45 catalytic site is conserved in Bh-EGase II. Bh-EGase II has three putative N-glycosylation sites at 56–58 (N–K–S), 99–101 (N–S–T), and 237–239 (N–Y–S), respectively. The cDNA encoding Bh-EGase II was expressed in baculovirus-infected insect BmN cells and Bombyx mori larvae. Recombinant Bh-EGase II from BmN cells and larval hemolymph had an enzymatic activity of approximately 928 U/mg. The enzymatic catalysis of recombinant Bh-EGase II showed the highest activity at 50 °C and pH 6.0.     

Host plant defenses of black (Solanum nigrum L.) and red nightshade (Solanum villosum Mill.) against specialist Solanaceae herbivore Leptinotarsa decemlineata (Say)

Black nightshade (Solanum nigrum, S. nigrum L.) and red nightshade ( Solanum villosum, S. villosum Mill.) are medicinal plants from the Solanaceae family that synthesize glycoalkaloids and other secondary metabolites. To recognize the potential insecticide activity of these compounds, leaf extracts (containing glycoalkaloid and methanol fractions) were tested for enzyme inhibition, antifeedant activity and toxicity. For in‐vitro glutathione S‐transferase (GST) inhibition activity, we used insecticide‐resistant Colorado potato beetle, Leptinotarsa decemlineata ( L. decemlineata; Say) midgut and fat‐body homogenate. In‐vivo toxicity and the antifeedant activity were performed using larval bioassays. The methanol extracts had greater GST inhibitory activity compared to the glycoalkaloids, as well as greater 2nd instar larvae mortality and antifeedant activity. Furthermore, the green leaf volatile compound, cis‐hex‐3‐enyl acetate, at the concentration of 5 ppm, caused 50% mortality of 2nd instar larvae. Our findings suggest the potential usefulness of S. nigrum and S. villosum extracts to control L. decemlineata.     

Insecticidal Metabolites from the Rhizomes of Veratrum album against Adults of Colorado Potato Beetle,Leptinotarsa decemlineata

The dried rhizomes of Veratrum album were individually extracted with CHCl₃, acetone, and NH₄OH/benzene to test the toxic effects against the Colorado potato beetle, Leptinotarsa decemlineata, which is an important agricultural pest. Fifteen compounds in various amounts were isolated from the extracts using column and thin‐layer chromatography. The chemical structures of 14 compounds were characterized as octacosan‐1‐ol ( 1 ), β‐sitosterol ( 2 ), stearic acid ( 3 ), diosgenin ( 4 ), resveratrol ( 5 ), wittifuran X ( 6 ), oxyresveratrol ( 7 ), β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 8 ), diosgenin 3‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐glucopyronoside ( 9 ), oxyresveratrol 3‐O‐β‐D ‐glucopyranoside ( 10 ), jervine ( 11 ), pseudojervine ( 13 ), 5,6‐dihydro‐1‐hydroxyjervine ( 14 ), and saccharose ( 15 ) using UV, IR, MS, ¹H‐ and ¹³C‐NMR, and 2D‐NMR spectroscopic methods. However, the chemical structure of 12 , an oligosaccharide, has not fully been elucidated. Compounds 4, 6, 9 , and 10 were isolated from V. album rhizomes for the first time in the current study. The toxic effects of three extracts (acetone, CHCl₃, and NH₄OH/benzene) and six metabolites, 2, 2 + 4, 5, 7, 8 , and 11 , were evaluated against the Colorado potato beetle. The assay revealed that all three extracts, and compounds 7, 8 , and 11 exhibited potent toxic effects against this pest. This is the first report on the evaluation of the toxic effects of the extracts and secondary metabolites of V. album rhizomes against L. decemlineata. Based on these results, it can be concluded that the extracts can be used as natural insecticides.     

Sperm utilization and post-copulatory female-guarding in the Colorado potato beetle, Leptinotarsa decemlineata

Crosses between white and black color morphs of the Colorado potato beetle, Leptinotarsa decemlineata Say, used as genetic markers, showed that male beetles ride and guard females to achieve the three copulations required to fill the spermatheca. Multiple matings are necessary for the females to realize their full reproductive potential. Sperm mixing occurs in the spermatheca providing partial sperm precedence. The data support the competitive mate searching theory.

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Résumé Différentes combinaisons d'accouplements entre des mutants noirs et blancs du doryphore de la pomme de terre, Leptinotarsa decemlineata, servirent à étudier le comportement de guarde de la femelle par le mâle après un premier accouplement. Les résultats indiquent que le sperme de deux mâles accouplant la même femelle se mélange dans la spermathèque assurant ainsi un certain niveau de précédence du sperme du dernier mâle.La masse de sperme dans la spermathèque était inférieure à sa capacité chez les femelles ayant été accouplées une ou deux fois. Le doryphore mâle aurait donc avantage à demeurer sur la femelle après un premier accouplement afin d'obtenir le minimum de trois accouplements requis pour remplir la spermathèque avant que les autres mâles puissent accoupler cette femelle. Les autres mâles ont avantage à essayer de dérober cette femelle pour remplir eux mêmes la spermathèque ou tout au moins profiter d'une certaine précédence du sperme du dernier mâle pour fertiliser une partie des oeufs.Sans accouplements multiples, la femelle ne possède pas suffisamment de sperme pour féconder tous ses oeufs. II semble aussi que les accouplements répétés puissent augmenter sa fécondité.Les résultats supportent une stratégie reproductive de compétition plutôt qu'une simple maximisation du nombre d'accouplements.

     

马铃薯甲虫两个系统性RNA干扰缺失基因cDNA的克隆、序列分析和时空表达

【目的】克隆马铃薯甲虫Leptinotarsa decemlineata(Say)两条Sid-1基因的全长并分析其时空表达。【方法】本研究通过RT-PCR和5'/3'RACE等技术从马铃薯甲虫中克隆全长序列,通过序列多重比对和系统发育分析研究序列的保守性和基因起源,通过阶段收样,组织解剖和qPCR技术获得这两个基因的时空表达。【结果】从马铃薯甲虫Leptinotarsa decemlineata的4龄幼虫中克隆得到LdeSid-1a和LdeSid-1c,其m RNA全长为2 887和3 733 bp,编码759和782个氨基酸,分子量为86.19和90.27 ku,两条蛋白质序列的相似性为59%。与其它昆虫的系统性RNA干扰缺失基因的比对结果显示,LdeSid-1a和LdeSid-1c分属于鞘翅目系统性RNA干扰缺失基因的两个分支,均具有典型的11个跨膜域结构,在蛋白质序列的N端具有4段高度保守的基序。qPCR的时序分析表明LdeSid-1a和LdeSid-1c的表达从初孵幼虫开始逐渐上升,而LdeSid-1c在卵中的表达也较高,组织中的分布结果表明,两个基因在所有组织中均表达,在前肠、中肠和后肠以及生殖系统中表达较高,在神经系统中为优势表达。LdeSid-1a和LdeSid-1c的Gen Bank登录号为KR153284和KR153285。【结论】LdeSid-1a和LdeSid-1c具有典型的系统性RNA干扰缺失基因家族的结构,时空表达和系统发育的结果均表明这两条基因可能在幼虫的高龄阶段起到重要作用。