Activity levels and predator detection by amphipods infected with an acanthocephalan parasite, Pomphorhynchus laevis

The acanthocephalan parasite Pomphorhynchus laevis (Müller, 1776) uses freshwater amphipods as its intermediate host. In order to complete the life cycle, the infected amphipod must be consumed by a fish, where the acanthocephalan will mature and reproduce. Parasite transmission, and therefore fitness, could be enhanced if infected amphipods fail to detect or avoid predatory fish. We compared the activity levels of infected and non-infected amphipods, Echinogammarus stammeri (Karaman, 1931), in both the presence and absence of odours from its natural, definitive host, the fish Leuciscus cephalus (L.). Throughout the experiment, infected amphipods were more active than were non-infected individuals. The non-infected amphipods reduced their activity after the addition of fish odours, but the infected amphipods failed to show a significant decrease. The failure of infected amphipods to reduce activity levels in the presence of fish odour may reflect a parasite strategy to increase its chances of transmission by making its amphipod host more vulnerable to predation by fish.     

Sense organs of the nematodes Trichinella pseudospiralis Garkavi, 1972 and T. nativa Britov et Boev, 1972

The structure and distribution of the sense organs of the head and the tail of two day-old Trichinella species (females) have been determined by transmission (TEM) and scanning (SEM) electron microscopy. In both species occur 16 cephalic sense organs, which contain three modified dendritic processes, in addition to the amphids. The nerve cell bodies are situated in the area above the nerve ring. The amphid contains ten dendritic processes. The sense organs open to the external environment by pores through the cuticle. Above the bulbous tip, the dendritic processes are surrounded by hypodermal cells. They enter posteriorly the pseudocoelom and join in subventral, subdorsal and two sublateral nerves, with transparent nuclei, in the area above the nerve ring. The distribution of the sense organs of larvae from the muscles and from the uterus is similar to that of the adults. The dendritic processes are short, most of their distal chamber is compacted with a dense, filamentous material. The rectum in the tail end of the female is innervated from the dorsal ganglion composed by multipolar cells with numerous dendrites and a single axon. Close to the excretory pore occurs a hemizonid which consists of six to eight dendrites and is situated between the hypodermis and the muscles. This organ has not been found in the larva.     

Parasitization by Cotesia plutellae enhances detoxifying enzyme activity in Plutella xylostella

Insecticidal tests using diazinon showed that the mortality of Plutella xylostella larvae parasitized by Cotesia plutellae was reduced by 4.6-fold compared to that of the nonparasitized hosts. The use of chemicals with synergistic effect to insecticides in toxicity assay helps to elucidate the kind of enzyme involved in lowering insect mortality. Synergism of diethyl maleate and piperonyl butoxide with diazinon resulted to 2.4- and 1.9-fold increase, respectively, in susceptibility of parasitized larvae compared to those of nonparasitized larvae. These results indicated the possibility that the decrease in susceptibility to diazinon was due to the elevated activities of glutathione-S-transferase (GST) and cytochrome P450 monooxygenase (CYP), respectively. The GST activities in parasitized larvae were significantly higher than those of nonparasitized ones starting from three days post-parasitization until emergence of parasitoid larva. High GST activities during late parasitism could be attributed to both enzyme activities toward diazinon of parasitized P. xylostella larva itself and C. plutellae larva inside larval host. High GST activity one day after parasitization, although statistical significance was not detected, was caused by polydnavirus (PDV) and the venom of C. plutellae not by parasitoid larvae. Artificial injection of PDV plus venom demonstrated that the resulting increase in GST activity is similar to the increase brought by parasitization. High CYP activity after 3 days post-parasitization in parasitized larva was attributed mainly to the activity of parasitoid larva. Carboxylesterase activity in the parasitized host remained at a high level, while that in the nonparasitized host decreased slightly as pupation approaches. On the other hand, acetylcholinesterase activity also remained constant after parasitization until larval emergence, while that of the nonparasitized hosts decreased gradually as the host larvae approach pupation. These results were supported by inhibition tests using diazoxon in vitro.     

Density ofAlabama argillacea larvae affects food extraction by females ofPodisus nigrispinus

The food extraction by adult females ofPodisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) from 3 ^rd instarAlabama argillacea (Hübner) larvae was evaluated in the laboratory. The densities studied were converted to weight of prey offered: 15.7 (one larva); 44.1 (three larvae); 71.4 (five larvae); 117.4 (seven larvae) and 148.8 mg (nine larvae). The adult weight, the amount of food consumed, the weight of remaining larvae and the time taken to ingest the food were recorded every 24 h during 9 days to estimate the percentage of food consumed, the quantity and the percentage of food extracted from each larva, the quantity of food extracted per minute and the relative consumption rate. The quantity of food consumed (88.5% to 35.5%) and extracted (90.8% to 35.5%) byP. nigrispinus females from each larva decreased as the food available increased. The time spent byP. nigrispinus to ingest food and the quantity of remaining food were similar during the 9-day period of the adult stage of this predator. No interactions were observed between the age of females of this predator and the prey density. The weight gained (1.2–5.8 mg/9 days), body weight (35.5–42.3 mg) and the relative consumption rate (0.4–1.4 mg/mg/day) by females of this predator increased at a declining rate with the quantity of food available.P. nigrispinus may change its predatory behavior as a function of food available. http://www.phytoparasitica.org posting Dec. 25, 2007.     

The kinetics of insecticide action. Part III: The use of stochastic modelling to investigate the pick-up of insecticides from ULV-treated surfaces by larvae of Spodoptera littoralis boisd

The pick-up of pesticide by lepidopterous larvae walking across ultra-low volume pesticide treated surfaces has been stochastically modelled and simulated using a computer. The duration of the random walk was considered as a series of small, discrete time intervals during which the mode of pick-up varied, depending upon the behavioural state (resting, feeding or walking) of a larva. Estimates can be obtained for the total mass picked up by the larva (gross) and the net amount eliminated, the internal exposure to insecticide, and the proportion of insects knocked down and killed with increasing time. The results of the simulation of Spodoptera littoralis larvae confined to permethrin-treated surfaces were in agreement with experimental data, and suggested that a high pick-up of insecticidal droplets resulted from adhesion of the pesticide to larvae following encounter. However, the availability of drops at the leaf surface decreased with time, probably as a result of droplet spread and subsequent uptake by the cuticular waxes. Droplet stability on leaf surfaces may be related to droplet size.     

Toxicity of dimethoate and fenoxycarb to honey bee brood (Apis mellifera), using a new in vitro standardized feeding method

A new in vitro method was devised to assess the effects of pesticides on honey bee brood. The method allowed the quantification of doses ingested by larvae and the assessment of larval and pupal mortality. Larval mortality in control samples was lower than 10%. Two active substances were tested: dimethoate and fenoxycarb. The LD(50) of dimethoate was 1.9 microg larva(-1) 48 h after oral exposure of larvae at day 4. Additional dose-related effects on pupal mortality were noted. After a chronic intoxication, the NOAEC (No Observed Adverse Effect Concentration) for larval mortality at day 7 was 2.5 mg kg(-1), whereas a NOAEC of 5 mg kg(-1) was found at day 22 for delayed effects on the reduction of adult emergence. Fenoxycarb applied at day 4 showed no effect on larvae, whereas emergence of adults was affected at doses higher than 6 ng larva(-1).     

水分对复苏后亚洲玉米螟越冬代幼虫化蛹的影响

作者对复苏后玉米螟的饮水作用研究表明,玉米螟幼虫摄取水分的过程是通过口器主动饮水,饮水后促进虫体重量增加、死亡率降低和提高化蛹率。在一定范围内,饮水量取决于饮水时间的长短。死亡率（Ｄ）和化蛹率（Ｐ）与饮水时间（ｔ）的关系为：Ｄ＝７０．５１８０ｔ＾－０．３５７６（ｒ＝０．９１８８＾＊＊）和Ｐ＝３．５８９９＋１．０５１０ｌｇｔ（ｒ＝０．９５３５＾＊＊）。饮水量（Ｘ）与化蛹率的关系：Ｐ＝０．８４０８Ｘ＾     

茶毒蛾步甲研究初报

茶毒蛾步甲的成、幼虫是茶毒蛾的主要捕食性天敌。一年两代,世代重叠,以成虫越冬,雌成虫寿命246—540天。一头幼虫一生能捕食3—6龄的茶毒幼虫33.2头,一头成虫在茶毒蛾一个世代中可捕食959头茶毒蛾幼虫。成虫在活动期能忍受饥饿55天,幼虫有相互残食习性。     

舞毒蛾脑和咽下神经节的形态及其三维模型构建

为探究舞毒蛾控制和分泌滞育激素的器官，于室内对舞毒蛾幼虫的中枢神经系统进行显微解剖，对其中枢神经系统和咽下神经节进行观察，并测量舞毒蛾1~5龄幼虫咽下神经节长度、宽度和面积，运用共聚焦激光扫描显微镜对脑和咽下神经节玻片逐层扫描，获取舞毒蛾幼虫脑和咽下神经节各高度的图像，将扫描后的图片描绘成1组多边图形，将其导入软件中，软件将多边图形叠加后构建其三维模型。结果显示，舞毒蛾幼虫的中枢神经系统包括脑、咽下神经节、3个胸部神经节和7个腹部神经节；舞毒蛾不同龄期幼虫的咽下神经节在外观形态上无较大差异；随着龄期增长，舞毒蛾咽下神经节的长度、宽度以及面积也不断增加，其中4龄幼虫咽下神经节的长度、宽度以及面积的增长速度最快，而5龄幼虫咽下神经节的长度、宽度以及面积的增长速度略微下降，1~3龄幼虫咽下神经节的长度、宽度以及面积的增长速度大致相同，均小于4龄和5龄幼虫。通过测量外部形态结构重建了舞毒蛾脑和咽下神经节的三维模型。     

取食不同寄主植物对韭菜迟眼蕈蚊幼虫药剂敏感性的影响及其生化机制

采用浸渍法研究了分别取食韭菜、大葱、圆葱和大蒜的韭菜迟眼蕈蚊4龄幼虫对大蒜油、苦参碱和辛硫磷的敏感性,用生化分析法测定了敌敌畏和大蒜油对幼虫体内乙酰胆碱酯酶和主要代谢酶活性的影响.结果表明:大蒜油对取食韭菜、大葱、圆葱和大蒜4龄幼虫的LC50分别为825.14、1202.2、1274.3和1412.4mg/L;辛硫磷分别为0.5437、1.1921、1.7713和1.9224mg/L,两种药剂对取食大蒜和圆葱幼虫的毒力较取食韭菜的差异显著.取食大蒜和圆葱的幼虫较取食韭菜的其体内乙酰胆碱酯酶活力降低,羧酸酯酶的活力明显提高,谷胱甘肽-S-转移酶的活力也有一定提高.寄主植物所含的硫醚类化合物对乙酰胆碱酯酶和代谢酶的诱导或抑制可能是引起药剂敏感性差异的主要原因.     

Basal stem rot of oil palm (Elaeis guineensis); mode of root infection and lower stem invasion by Ganoderma boninense

Reproducible infection of intact roots of oil palm ( Elaeis guineensis ) with Ganoderma boninense , the cause of basal stem rot, showed penetration followed by rapid longitudinal progression of hyphae and colonization of the lower stem (bole). Light and transmission electron microscopy showed invasion of the root cortex, with no evidence of selective progression through the vascular system or lacunae. In newly colonized tissue the fungus behaved as a hemibiotroph, with numerous, wide, intracellular hyphae occupying entire host cells that possessed intact cell walls and contained discernible cytoplasm and organelles. In the bole this phase coincided with a complete depletion of previously abundant starch grains in advance of invasion. Subsequently, in the roots and colonized stem base, widespread necrotrophic, enzymatic attack of all layers of the host cell walls occurred. Hyphae were intra- and intercellular and intramural and associated host cell wall degradation was often at a distance from hyphae, resulting in cavities within cell walls. A third developmental stage was the formation of an extensive, melanized, tough mycelium or pseudo-sclerotium which surrounded roots and comprised many very thick-walled cells encasing more typical thin-walled hyphae. Macroscopic observation of and isolation from the bole of randomly felled, commercial palms provided confirmatory evidence that multiple infections originated in the roots before spreading into the base of long-established palms.     

用松褐天牛幼虫繁殖花绒寄甲产出成虫的数量和质量

为了提高花绒寄甲Dastarcus helophoroides（Fairmaire）对松褐天牛Monochamus alternatus Hope的寄生率,我们用松褐天牛幼虫繁殖花绒寄甲,研究不同接虫量和不同接虫时间对产出花绒寄甲成虫的影响。结果表明：用4龄松褐天牛幼虫繁殖花绒寄甲最好,1头幼虫接4头初孵花绒寄甲幼虫的产出率最高,为77.7%;产出量最大,平均为3.11头,而且产出的花绒寄甲成虫体长最长,平均为8.02 mm,体宽也最宽,平均为3.09 mm。在花绒寄甲幼虫孵化当天即接种,产出的成虫体长最长,平均为8.01 mm,体宽最宽,平均为3.10 mm。因此,最佳接虫量为每头松褐天牛幼虫接4头花绒寄甲幼虫,最佳接虫时间是花绒寄甲幼虫从卵中孵化出的当天。单头天牛幼虫产出的花绒寄甲成虫的数量对其个体大小影响均不显著。     

Toxicity of some juvenile hormone-active compounds forspodoptera littoralis boisd. larvae

Six juvenile hormone analogues, compounds 6–9550, 8–4314, and 20–3600 of Dr. R. Maag Ltd., Switzerland, and compounds ZR-512, ZR-515 and ZR-619 of Zoecon Corp., U.S.A., were tested against big and medium-size larvae ofS. littoralis Boisd. by topical application. Compounds 6–9550 and 8–4314 were slightly active against big larvae and inactive against medium-size larvae; ZR-512 was moderately active against big and inactive against medium-size larvae. The other three compounds caused 90% mortality in big larvae: 20–3600 at 20μg/larva and ZR-515 and ZR-619 at 5μg/larva. ZR-512 and ZR-619 were less toxic for medium-size larvae than for big larvae, whereas 20–3600 was about equitoxic for larvae of both sizes     

昆明山海棠杀虫活性成分雷公藤定碱和雷公藤次碱的触杀作用及对Na+ -K+ -ATP酶活性的影响

为进一步探讨杀虫植物昆明山海棠根皮中分离出的雷公藤定碱和雷公藤次碱的杀虫作用机理,采用微量点滴法处理3龄粘虫前胸背板,观察发现试虫均在2 h左右表现出中毒麻醉,8 h后完全恢复,24 h后重新表现为中毒麻醉,48 h后部分死亡。进一步的触杀毒力测定结果表明,雷公藤定碱和雷公藤次碱对3龄粘虫幼虫的24 h麻醉中量分别为8.82 μg/头和 4.58 μg/头,对3龄小菜蛾幼虫的麻醉中量分别为4.71 μg/头和3.46 μg/头。离体和活体条件下测定了雷公藤定碱和雷公藤次碱对5龄粘虫幼虫头部Na+-K+-ATP酶活性的影响,结果表明,两种药剂对粘虫幼虫神经系统Na+-K+-ATP酶活性均有一定的抑制作用,且该抑制作用具有一定的浓度依赖性,推测Na+-K+-ATP酶可能是雷公藤定碱和雷公藤次碱的一个重要作用靶标。     

溪岸蠼螋对棉铃虫的捕食能力

为明确棉田溪岸蠼螋 Labidura riparia 对棉铃虫的控害潜能, 在实验室条件下观察和测定了溪岸蠼螋不同龄期的若虫、雌雄成虫对棉铃虫幼虫、蛹和成虫的捕食能力以及其5龄若虫和雌雄成虫的捕食选择性。结果表明:不同发育阶段的溪岸蠼螋都不捕食棉铃虫完整的蛹体, 但对棉铃虫幼虫和成虫都具有较强的捕食能力。其中, 雌性溪岸蠼螋成虫的捕食能力最强, 对棉铃虫1龄幼虫日捕食量最大, 为(31.3±1.1)头。1龄溪岸蠼螋若虫也具有一定的捕食能力, 对棉铃虫1龄幼虫日捕食量为(1.7±0.7)头。不同龄期的溪岸蠼螋对相同龄期棉铃虫幼虫的捕食能力随龄期增加而增大。对1~3龄棉铃虫幼虫,溪岸蠼螋雌成虫捕食能力最强,其次是溪岸蠼螋雄成虫,再次是溪岸蠼螋5龄若虫。但是,对棉铃虫4~6龄幼虫和雌雄成虫,溪岸蠼螋雌雄成虫和5龄若虫的捕食量差异不显著。捕食选择试验表明:溪岸蠼螋5龄若虫和雌雄成虫对棉铃虫1～4龄幼虫均表现正喜好性, 对5～6龄棉铃虫幼虫和雌雄成虫表现负喜好性。     

大豆品种对斜纹夜蛾的抗性机制初探

在肉室人工接虫条件下研究大豆３个高抗品种吴江青豆３、通山薄皮黄豆甲、赶泰－２－和３个高感品种皖８２－１７８、山东大豆及Ｍｏｒｓｏｙ对斜纹夜蛾的抗性表现。结果表明,抗感材料间以叶面积损失率为指标的抗虫性差异极为,而对斜纹夜蛾产卵排趋性差异不显著。     

三种寄主植物对小菜蛾实验种群特征的影响

为明确萝卜、白菜和油菜对小菜蛾实验种群特征的影响,测定了小菜蛾对3种寄主的取食量,通过构建两性生命表比较了不同寄主植物对其实验种群发育与繁殖的影响,并综合生命表与取食量参数,评价了小菜蛾对萝卜、白菜和油菜的危害。结果显示:小菜蛾幼虫在萝卜、油菜和白菜上的取食量差异显著,分别为93.3、105.0和114.7 mg/头。小菜蛾取食萝卜、白菜和油菜后,其幼虫的发育历期差异显著,依次为8.6、8.5和7.6 d;种群内禀增长率依次为0.18、0.23和0.23,周限增长率为1.19、1.26和1.26,净生殖率为18.7、46.1和30.6。取食萝卜的小菜蛾各发育阶段的存活率最低。小菜蛾对各供试寄主实际危害量占理论危害量的百分比为油菜(71.8%)白菜(70.8%)萝卜(53.0%)。表明同一时间内,小菜蛾对油菜危害程度最大,白菜次之,萝卜最小。     

Comparative activity of Choristoneura fumiferana nucleopolyhedrovirus propagated in different hosts

The biological activity of the Ireland strain of Choristoneura fumiferana (Clem) nucleopolyhedrovirus (CfMNPV) propagated in different hosts was determined to provide the basis upon which genetically modified CfMNPV, or other naturally occurring isolates, should be compared. Occlusion bodies (OB) derived from CF-203 cells were significantly larger and more pathogenic than those propagated in vivo when tested against the fifth larval instar of C fumiferana (Clem) and C occidentalis Freeman. The dose-responses (LD50 and LD95, expressed as occlusion bodies per larva) of C fumiferana larvae to in vitro-propagated OBs were 274 and 5785, respectively. The values of LD50 and LD95 to C occidentalis larvae were 19 and 118, respectively. There were no significant differences in pathogenicity or size when OBs propagated in C fumiferana larvae were tested against either insect species, nor were there significant differences for OBs propagated in C occidentalis larvae. The LD50 and LD95 of in vivo-produced OBs to C fumiferana were 925 and 61988, respectively. The LD50 and LD95 to C occidentalis were 50 and 453, respectively. OBs propagated in vitro had a mean volume of 13.13 microm3, whereas those propagated in vivo ranged from 0.84 to 1.41 microm3. The median survival time-responses (ST50) of fifth-instar C fumiferana or C occidentalis larvae to OBs propagated in vivo were not significantly different from those propagated in vitro at the dosage levels tested. Values of ST50 of C fumiferana larvae to in vitro- and in vivo-produced OBs at dosages causing less than 50% mortality rangedfrom 9.6 to 9.8 days post-inoculation (dpi), whereas a LD95 dose resulted in ST50 values ranging from 7.3 to 7.7 days. ST50 values of C occidentalis larvae at dosages causing less than 50% mortality ranged from 9.8 to 10.2 dpi, whereas a LD95 dose resulted in ST50 values ranging from 9.5 to 9.8 dpi. The median feeding cessation time-response (FT50) of fifth-instar C fumiferana larvae to OBs propagated in vitro (5.7 days) was not significantly different from the FT50 of those propagated in vivo in either insect species (5.3 and 5.7 days) at the dosage level tested (LD95). No significant differences in FT50 values were observed between OBs propagated in either larval host. The FT50 of C occidentalis larvae to OBs propagated in vitro (7.7 days) was not significantly different from that to those propagated in vivo in C occidentalis larvae (7.6days), but somewhat different (7.2 days) from that to those propagated in C fumiferana larvae. Results indicate that CfMNPV can be propagated in vivo in either C fumiferana or C occidentalis larvae (or sequentially through both) without alteration in infectivity, although the use of the CF-203 cell line yields the most biologically active OBs.     

Optimization of production of nucleopolyhedrovirus ofHelicoverpa armigera throughout larval stages

Studies were carried out to optimize production of nucleopolyhedrovirus of American bollworm,Helicoverpa armigera (Hübner), by treating larvae individually with an inoculum dose that allowed maximal larval growth and also gave the highest occlusion bodies (OB) yield/larva. The maximum virus yield of 12.2x 10⁹ OB/larva was obtained when 6-day-old larvae were fed individually with a dose of 1 x 10³ OB. Topical spiracular treatment of larvae as old as 8 days with 10 μ of 2x 10⁷ OB ml^-1 gave the highest yield, of 15.2x 10⁹ OB from 13-day-old larvae, of 12.8x 10⁸ OB from prepupae and of 1.49x 10⁸ OB from pupae at the time of their death. These studies showed that dietary inoculum is the best route for 6-day-old larvae and topical spiracular treatment is the best for 8-day-old larvae.     

异色瓢虫幼虫对云南云杉长足大蚜若虫的捕食效应

在室内研究了捕食性天敌异色瓢虫4龄幼虫对云南云杉长足大蚜若虫的捕食作用。结果表明,异色瓢虫对云南云杉长足大蚜若虫的捕食功能反应符合HollingⅡ型反应,拟合的圆盘方程为N_a=1.028 9 N_t/(1+0.009 8 N_t)。根据HollingⅢ型功能反应新模型N_a=a·exp~(-b/N_t)计算出最佳寻找密度43.54头;在猎物密度一定的情况下,利用其捕食作用率与个体间相互干扰作用的关系用Hassell-Varley的干扰反应模型拟合为E=0.242 4P~(-0.398 5);分摊竞争强度与其密度的关系式为I=0.005 4lgP+0.679 6。利用Holling(1959)寻找效应(E)与猎物密度(N_t)关系式计算了寻找效应;利用HassellVarley(1969)模型和Beddington(1975)2种模型对异色瓢虫4龄幼虫寻找效应和自身密度之间的关系进行了模拟,模拟方程分别为:E=0.748 7P~(-1.298 4)、E=1.021 3/(2.479 4P-1.479 4)和E=1.021 3/(0.01 N_a+2.479 4P-1.479 4),异色瓢虫对云南云杉长足大蚜的寻找效应随猎物密度及捕食者密度的增加而下降。