Effect of intraguild predation on the survival and development of three species of aphidophagous ladybirds: consequences for invasive species

Abstract 1 Survival and development of hatchling larvae of three aphidophagous ladybirds (Coleoptera: Coccinellidae), Harmonia axyridis Pallas, Coccinella septempunctata brucki Mulsant and Adalia bipunctata Linnaeus, when fed their own and the other species eggs were recorded. 2 In all three species, the larvae survived when fed conspecific eggs. 3 The percentage of larvae of H. axyridis that survived decreased to 35% and 85% when fed eggs of A. bipunctata and C. s. brucki, respectively. All the larvae of A. bipunctata and C. s. brucki died after eating eggs of H. axyridis. None of the larvae of C. s. brucki died after eating eggs of A. bipunctata, whereas 46% of those of A. bipunctata died after eating eggs of C. s. brucki. 4 In general, larvae were reluctant to eat the eggs of other species. However, larvae of C. s. brucki showed less reluctance than H. axyridis to eat the eggs of A. bipunctata. 5 The consequence of this for invasive species of ladybird is discussed.     

异色瓢虫酪氨酸羟化酶基因不同发育历期表达及RNAi抑制黑化效果分析

酪氨酸代谢在昆虫黑色素形成中具有重要的调控作用。本研究为探讨酪氨酸代谢调控异色瓢虫黑色素代谢平衡及其发育的影响,先检测异色瓢虫不同发育阶段酪氨酸羟化酶(Tyrosine hydroxylase,TH)基因表达情况,采用RNAi技术对4龄幼虫注射dsTH RNA抑制酪氨酸羟化酶mRNA表达,探索其在蛹期和成虫羽化阶段黑色素形成中的潜在功能。研究结果表明,TH基因在4龄幼虫体内的表达量最高,而在预蛹阶段和羽化后第2天开始表达量显著性下降。其次,dsTH RNA注射后能够显著降低TH本基因的表达,且异色瓢虫4龄幼虫发育缩短,与注射dsGFP RNA组相比较,提前化蛹。最后,dsTH RNA注射后异色瓢虫蛹的重量略有增加,且发育出现异常,即蛹的颜色变化不加深,与对照组相比较,无黑色斑点出现。这些结果表明成虫是在蛹期开始形成黑色素的,及酪氨酸羟化酶能够通过调控酪氨酸代谢途径而影响异色瓢虫化蛹阶段的发育和表皮颜色的变化。相关研究结果有助于丰富酪氨酸代谢调控异色瓢虫表型的内容,为将来保护异色瓢虫,并将其用于害虫生物防治提供理论基础。     

外源保幼激素对异色瓢虫卵巢发育及生殖相关基因转录水平的影响

【目的】本研究旨在明确外源保幼激素(juvenile hormone, JH)对异色瓢虫Harmonia axyridis成虫卵巢发育以及生殖信号通路中关键基因转录水平的影响。【方法】以萝卜蚜Lipaphis erysimi饲喂的异色瓢虫雌成虫为空白对照组,以点滴同体积丙酮的雌成虫为溶剂对照组,对人工饲料饲喂的羽化后第2天的雌成虫点滴不同剂量(80, 120和160 ng/头)JHⅢ 1, 3, 5, 7和9 d后,解剖成虫卵巢,拍照并测量卵巢长度及其第一卵室的长度和宽度。利用qPCR分析在最适JHⅢ剂量(120 ng/头)处理后1, 5和9 d的异色瓢虫雌成虫生殖信号通路中关键基因JH受体methoprene-tolerant (Met)基因、krüppel homolog 1(Kr-h1)基因、卵黄原蛋白(vitellogenin, Vg)基因(Vg1和Vg2)和卵黄原蛋白受体(vitellogeninreceptor, VgR)基因表达水平。【结果】与溶剂对照组相比,点滴80和120 ng/头剂量JHⅢ可促进异色瓢虫成虫卵巢发育,其中120 ng/头剂量JHⅢ处理羽化后第2天雌成虫后7 d卵巢中出现大量卵黄沉积,与萝卜蚜饲喂的空白对照组卵巢发育状态一致,卵巢长度以及第一卵室的长度和宽度均显著高于溶剂对照组的;160 ng/头剂量JHⅢ处理则抑制卵巢发育。qPCR结果表明,120 ng/头剂量JHⅢ处理后5和9 d雌成虫中HaMet, HaKr-h1, HaVg1, HaVg2和HaVgR基因表达量较对照组(丙酮处理组)均增加,其中处理后5 dHaMet, HaVg1和HaVgR基因表达量分别为对照组的2.78, 13.14和8.28倍,处理后9 d分别为对照组的2.36,1.85和2.01倍,差异极显著。【结论】120 ng/头JHⅢ可促进异色瓢虫成虫卵巢发育,上调处理后5和9 d时雌成虫HaMet, HaKr-h1, HaVg和HaVgR基因表达量;推测这些关键基因在保幼激素调控异色瓢虫卵巢发育及卵黄形成过程发挥重要作用。     

Role of social and individual experience in interaction of the meadow ant Formica pratensis (Hymenoptera: Formicidae) with ladybird imagines and hoverfly larvae

The ability to recognize aphidophages is one of the key points in the protection ants provide aphids against their natural enemies. Behavior of honeydew collectors from nature (“field,” control) and laboratory reared “naive” ants of Formica pratensis Retzius, which had never met either “mature” workers or aphids and aphidophages, was observed during their pairwise interactions with ladybird imagines and hoverfly larvae. The majority of the “naive” ants perceived ladybirds as an enemy at their first encounter attacking them immediately without any prior antennation. Ants seem to have a certain innate “enemy image” that lets them react very quickly to protect aphids. Hoverfly larvae were rarely attacked by both “field” and “naive” ants (>15%). During tests with ladybirds ants from nature attacked them and also demonstrated the most aggressive reactions (series of bites and “death grip”) less frequently than the “naive” ants. The percentage of ants avoiding aphidophages after a contact with their chemical defense (reflex bleeding and glue‐like saliva) was significantly higher in the control group. Whereas the “naive” ants did not learn to avoid danger, foragers from nature usually tried to avoid negative experience and used tactics of “short bites.” Overall, experience has been proved to be unimportant for displaying key behavioral reactions underlying ant–ladybird interaction. However, accumulation of experience has been assumed to play an important role in the formation of behavioral strategy that allows honeydew collectors to drive aphidophages away with lower energy costs and avoid or minimize negative consequences of aphidophages’ chemical defense.     

Entomopathogenic fungi recorded from the harlequin ladybird, Harmonia axyridis

Entomopathogenic fungi were recorded from field samples of the harlequin ladybird Harmonia axyridis, an invasive coccinellid that has recently arrived in Denmark. Larvae, pupae and adults were found to be infected by Isaria farinosa, Beauveria bassiana and species of Lecanicillium. This is the first record of entomopathogenic fungi infecting larvae and pupae. Winter mortality due to fungal infection reached 17.9% in adults collected at one location. The larval stage was most susceptible to fungal infection, as confirmed through bioassay with I. farinosa.     

Soybean Aphid Predators in Québec and the Suitability of Aphis glycines as Prey for Three Coccinellidae

Since its invasion of North America in 2000, the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae) has notably changed the arthropod community of the soybean agroecosystem. The objectives of this study were to characterize the foliar predatory fauna associated with A. glycines in commercial soybean fields in Québec, Canada, and to evaluate the suitability of A. glycines as prey for three coccinellid species: Harmonia axyridis Pallas, Propylea quatuordecimpunctata L. and Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Field surveys showed that several predators responded rapidly to expanding and increasing populations of the soybean aphid. Coccinellidae were the most important aphidophagous predators observed in 2002 (58.6%) and 2003 (44.8%), with mainly four native and naturalized species co-occurring with the soybean aphid throughout the growing season. Measurement of fitness parameters under laboratory conditions (survival, development time, longevity, fecundity) indicated that A. glycines is an excellent prey for the development and reproduction of all three of the coccinellid species studied. The intrinsic rate of natural increase (r_m) was highest for H. axyridis (0.238 d⁻¹), intermediate for P. quatuordecimpunctata (0.215 d⁻¹) and lowest for C. maculata (0.134 d⁻¹).     

异色瓢虫视觉系统中5-HT阳性神经元的分布

本文运用树脂石蜡（Colophony-Paraffin,CP;专利号：ZL98125709．7）组织包埋切片技术,结合免疫组织化学链酶菌抗生物素蛋白一过氧化物酶（Streptavidin-Peroxidase,SP）双染法,对异色瓢虫视觉系统中5-羟色胺（5-HT）能神经元的分布进行了初步研究。结果显示,异色瓢虫视觉系统的结构及5-HT免疫反应系统相对比较特殊。5-HT阳性神经元胞体数目较少,染色显著,并聚集成群。根据胞体定位、细胞形态及轴突走向,可大体分为5群,其中包括1群呈弱反应的光感细胞。5-HT阳性膨大纤维支配所有的视神经纤维网,并呈柱状或分层排列模式。结果表明5-HT作为经典的神经递质在昆虫的视觉信息处理过程中可能发挥重要的调节作用,且主要以远距离的广域神经调节模式为主,并在特定区域和GABA有伴随现象。此外,昆虫视觉系统中5-HT的含量还可能与其明暗适应的生理调节方式具有相关性[动物学报51（5）：912—918,2005]。     

瓢虫种群对棉花-玉米农田景观格局的响应

本文研究了华北棉花-玉米农田景观格局中龟纹瓢虫Propylaea japonica(Thunberg)和异色瓢虫Harmonia axyridis(Pallas)种群动态,发现农田景观格局中作物类型(棉花与玉米)对两种瓢虫种群密度动态有显著的影响,两种天敌瓢虫都趋向在玉米斑块上栖息。两种瓢虫在棉花斑块上呈现出时间分化,其中龟纹瓢虫在棉花种植的前中期种群密度较大,后期较少;而异色瓢虫在棉花前中期种群密度较少,后期较多,表明农田景观中种植玉米有利于增强瓢虫对棉花害虫的控制作用。进一步的研究表明,农田景观系统中玉米斑块所占的面积比对龟纹瓢虫和异色瓢虫种群密度均产生显著影响。这说明在农田景观系统中开展区域性生态调控的时候,需要考虑到各类斑块组合的面积比例,从而有利于增强多种天敌昆虫的协调控害作用。     

海藻糖酶基因TRE2-like和TRE2在异色瓢虫羽化过程中的表达与功能

【目的】异色瓢虫Harmonia axyridis是一种重要的捕食性天敌昆虫,海藻糖在异色瓢虫的变态发育、羽化等整个生命过程都起着重要的作用。本研究以前期获得的类似膜结合型海藻糖酶(TRE2-like)与膜结合型海藻糖酶(TRE2)基因为基础,探讨在异色瓢虫羽化阶段这两个海藻糖酶的潜在功能,为阐明异色瓢虫从蛹发育到成虫时海藻糖代谢机制提供参考。【方法】根据TRE2-like和TRE2基因序列设计双链RNA(dsRNA)区域片段并合成对应的dsRNA,通过RNAi将其注射到异色瓢虫2日龄蛹中。采用实时荧光定量PCR(RT-qPCR)检测RNAi处理后羽化第1天的异色瓢虫成虫糖代谢相关基因的表达;同时采用蒽酮比色法、酶标法等分别测定RNAi处理后羽化第1天的异色瓢虫成虫主要糖类物质含量及TRE活性变化,并观察异色瓢虫羽化后的表型变化。【结果】结果表明,与对照组(dsGFP注射组)相比,异色瓢虫2日龄蛹被注射TRE2-like或TRE2 dsRNA后,其新羽化成虫体内TRE2-like和TRE2表达量均极显著下调,且少数个体出现了蜕皮与翅形成困难等畸形表型。可溶性海藻糖酶活性在注射dsTRE2-like后显著降低,膜结合型海藻糖酶活性在注射dsTRE2后显著降低;注射dsTRE2后糖原含量显著下降,注射dsTRE2-like后糖原和海藻糖含量显著下降,注射dsTRE2-like+dsTRE2后糖原和葡萄糖含量显著下降,且海藻糖含量极显著下降。注射dsTRE2-like, dsTRE2和dsTRE2-like+dsTRE2后可溶性海藻糖酶基因TRE1-1和TRE1-2表达下降或显著下降,而TRE1-5表达上升或显著上升,海藻糖合成酶(trealose-6-phosphate synthase, TPS)、糖原磷酸化酶(glycogen phosphorylase, GP)、糖原合成酶(glycogen synthase, GS)基因的表达均显著下调。【结论】TRE2-like和TRE2基因表达被抑制后,异色瓢虫海藻糖等代谢受到影响。研究结果为探究异色瓢虫体内膜结合型海藻糖酶的潜在功能和调控机制奠定了基础。