Ecdysteroid levels changed by permethrin action in female Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) ticks

As recent studies have shown that ecdysteroids may play a major role in the regulation of vitellogenesis in Ixodidae, the present study quantified, by means of a radioimmunoassay, the levels of ecdysteroids present in the hemolymph of semi-engorged females of Rhipicephalus sanguineus ticks obtained from control females (exposed to distilled water) and those exposed to increasing concentrations of permethrin. The levels of ecdysteroids decreased significantly as the concentration of permethrin increased, suggesting that this compound could be an inhibitor of ecdysteroids secretion, and consequently interfering with the reproductive ability of these ticks, since this hormone is responsible for the synthesis and incorporation of vitellogenin by oocytes. This study complements the previous results with R. sanguineus semi-engorged females, showing that permethrin is a potent agent causing major morphological changes in tick oocytes, such as the appearance of large vacuoles in the cytoplasm, reduction in the amount of yolk granules and a decrease in oocyte size, thus culminating in cell death and consequently reducing or preventing reproduction in treated females. The findings that permethrin leads to a decrease in ecdysteroid titers could represent an entry step into this scenario.     

化肥磷酸二铵对花背蟾蜍蝌蚪发育的影响

目的为了探究化肥磷酸二铵对两栖类幼体发育的影响。方法以花背蟾蜍(Bufo raddei)蝌蚪为研究对象,用化肥磷酸二铵(DAP)进行染毒培育,并依据Gosner(1960)分期标准,将蝌蚪分为G0实验组和G20实验组,分别暴露于浓度为0.045g/L、0.135g/L、0.225g/L的DAP水溶液中,直至蝌蚪完成变态发育,并对孵化率、死亡率、畸形率以及发育时程等参数进行统计分析。结果随着化肥DAP浓度的升高,孵化率逐渐下降,但对照组与各侵染组之间均无显著性差异;侵染组蝌蚪死亡率均高于对照组,均呈极显著性差异(P0.01),且G20侵染组明显高于G0侵染组;蝌蚪畸形可分为四大类,侵染组蝌蚪畸形率均高于对照组,且均呈极显著性差异(P0.01),畸形率随着DAP浓度的升高而增加;完成变态发育所用时程,侵染组明显长于对照组。结论化肥磷酸二铵对蝌蚪发育具有显著影响及损伤。     

The joint toxicity of type I, II, and nonester pyrethroid insecticides

Evidence suggests that there are separate binding domains for type I and II pyrethroid insecticides on the voltage gated sodium channel of the nerve cell axon, but there are no studies that have examined the mixture toxicity of nonester pyrethroids and type I and II pyrethroids. Therefore, we examined the effect of nonester pyrethroid (etofenprox), type I (permethrin), and type II (cypermethrin) pyrethroid insecticides alone and in all combinations to Drosophila melanogaster Meigen. The combination of permethrin + etofenprox and permethrin + cypermethrin demonstrated antagonistic toxicity, while the combination of cypermethrin + etofenprox demonstrated synergistic toxicity. The mixture ofpermethrin + cypermethrin + etofenprox demonstrated additive toxicity. The toxicity of permethrin + cypermethrin was significantly lower than the toxicity of cypermethrin alone, but the combination was not significantly different from permethrin alone. The toxicity of permethrin + cypermethrin + etofenprox was significantly greater than the toxicity of both permethrin and etofenprox alone, but it was significantly lower than cypermethrin alone. The mixture of permethrin and etofenprox was significantly less toxic than permethrin. The explanation for the decreased toxicity observed is most likely because of the competitive binding at the voltage-gated sodium channel, which is supported by physiological and biochemical studies of pyrethroids. Our results demonstrate that the assumption that the mixture toxicity of pyrethroids would be additive is not adequate for modeling the mixture toxicity of pyrethroids to insects.     

The cause of the decreased number of primordial germ cells in albino Xenopus resides not in the micro-environment but in the presumptive PGC

The number of primordial germ cells (PGC) in albino tadpoles of Xenopus is significantly decreased as compared with that of the wild-type. Whether the decreased number of PGC is caused by the presumptive PGC (pPGC) themselves or the micro-environment surrounding those cells in the albino, or both was investigated in the present study. [³H]thymidine-labeled pPGC of wild-type and albino were implanted into unlabeled, host neurulae of wild-type br albino and wild-type, respectively. Labeled PGC in the genital ridges of experimental tadpoles were examined by autoradiography. There were no significant differences in the proportion of tadpoles with labeled PGC and in the average number of those PGC between the albino and wild-type tadpoles, into which wild-type pPGC had been implanted. The proportion in wild-type tadpoles with albino pPGC was much lower than that in wild-type tadpoles with wild-type pPGC. These results suggest that the pPGC of the albino and not the micro-environment are responsible for the decreased number of PGC.     

The differential influence of protein kinase inhibitors on retinal arbor morphology and eye-specific stripes in the frog retinotectal system

We investigated retinal axon morphology and eye-specific afferent termination zones in the optic tectum of three-eyed tadpoles that were chronically treated with protein kinase inhibitors. The kinase inhibitors sphingosine, H-7, and phorbol ester, which down-regulates protein kinase C with chronic exposure, were applied to the tecta in a slow release plastic, Elvax. In vivo protein phosphorylation assays in drug-treated tadpoles indicated that the treatments decreased 32P incorporation into some protein bands by as much as 60%. Although the drugs did not cause a desegregation of the eye-specific stripes, treated retinal axon arbors covered about half the area covered by untreated arbors or arbors treated with inactive analogs of the drugs. We conclude that eye-specific segregation can be maintained under conditions that markedly alter retinal ganglion cell axon arbor size and that significantly perturb protein phosphorylation. Furthermore, we conclude that the protein kinase(s) that we blocked with these treatments is involved in the growth of axon arbors.     

Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg⁻¹), P2: medium (25 mg kg⁻¹) and P3: high (250 mg kg⁻¹)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.     

Phenotypic variation in adult behavioral response and offspring fitness in Plutella xylostella (Lepidoptera: Plutellidae) in response to permethrin

Phenotypic variation in behavioral response and physiological tolerance to permethrin was measured and compared between two populations of diamondback moth, Plutella xylostella (L.). A field population from Celeryville, OH, and a laboratory population originally collected from Wooster, OH, were compared. In laboratory choice bioassays, females from both populations were less likely to oviposit on cabbage leaf disks and seedlings treated with permethrin. The oviposition-deterrent effect was positively related to permethrin concentration. The laboratory population was significantly more behaviorally responsive to the insecticide and showed a significantly greater avoidance than the field population of the highest concentration of permethrin tested (1.50 g [AI] /liter). The physiological response of each population was measured by feeding bioassays, and the laboratory population was physiologically more susceptible to the permethrin. Larvae from the laboratory population that were fed permethrin-treated leaves had significantly lower growth rate, higher mortality, and lower adult fecundity compared with larvae from the field population. These data suggest that female moths that are more behaviorally responsive to permethrin produce offspring that tend to be more susceptible to the same insecticide, at least for the populations tested. The relationship between adult behavioral response and larval physiological tolerance to permethrin is discussed.     

花姬蛙蝌蚪对藻类的捕食效应

对花姬蛙(Microhyla pulchra)蝌蚪捕食藻类的效应进行了初步研究。结果表明,随着蝌蚪密度的增加,对蓝藻的总捕食量显著增加,但每只蝌蚪的平均捕食量随蝌蚪密度的增加而下降。文中讨论了蝌蚪在水资源环境保护中控制蓝藻暴发的意义。     

Electrophoretic analysis of intestinal acid phosphatase and N-acetyl-beta-glucosaminidase in the Discoglossus tadpole treated by thyroxine]

Polyacrylamide gel electrophoresis has been used to separate the two isoenzymes of intestional acid phosphatase (PI and P2) and N-acetyl-beta-glucosaminidase (G1 and G2) in Discoglossus pictus tadpoles treated by thyroxine. When the isoenzyme activities of each pair are expressed as percentages, the activity of the slower form (P2 or G2) increases significantly when the tadpoles are treated by the hormone.     

Release of piperonyl butoxide and permethrin from synergized ear tags on cattle and effects on horn fly mortality

A study was conducted to determine the release rates of piperonyl butoxide (PBO) and permethrin from synergized insecticidal cattle ear tags and their effects on mortality of the horn fly, Hematobia irritans irritans (L.) (Diptera: Muscidae). PBO was released from the ear tags at a higher rate than permethrin in both winter and summer trials. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the winter trial was 50.4 and 30.3%, respectively. The cumulative release of PBO and permethrin from the ear tags at the end of 18 wk in the summer trial was 66.7 and 44.7%, respectively. There was a significant correlation between the cumulative daily high ambient temperature (degrees C) and the cumulative release of both PBO and permethrin. Compared with the susceptible horn fly strain, the permethrin-resistant strain demonstrated 7.9- and 12.8-fold resistance to permethrin at the levels of LC50 and LC90, respectively. When exposed to filter paper wipes taken from the shoulders of cattle treated with the PBO-synergized permethrin tags from the summer trial, the resistant strain demonstrated reduced mortality compared with the susceptible strain. The mortality of the resistant strain at 2- and 3-h exposure exhibited a pattern of declining fly mortalities as a result of the decreased release of PBO and permethrin, as well as the decline in the ratio of PBO:permethrin released from the tags after 8 wk. A similar decline in horn fly mortalities was observed in the susceptible strain at 30-min exposure time that coincided with the pattern of reduced release of PBO and permethrin from the ear tags over the course of summer trial.     

Study of the sustained speed of kill of the combination of fipronil/amitraz/(S)-methoprene and the combination of imidacloprid/permethrin against Dermacentor reticulatus, the European dog tick

The sustained speed of kill against Dermacentor reticulatus of two topical combinations, one containing fipronil/amitraz/(S)-methoprene and the other, imidacloprid/permethrin, was evaluated in dogs. Two treated groups and one untreated control group of eight adult Beagle dogs each were randomly formed based on pre-infestation rates and bodyweight. Each treatment was administered topically once on Day 0, according to the recommended label dose and instructions for use. All dogs were infested with 50 adult unfed D. reticulatus starting on Day 1, then weekly, for a total of five weeks. While most studies determine tick efficacy at 48 hours (h), in this study, all remaining ticks were counted and categorized 24 h following each infestation. The numbers of ticks (living or dead) that remained attached on treated dogs were compared to those on the control animals. The percent reduction of attached ticks (disruption of attachment) at 24 h on dogs treated with fipronil/amitraz/(S)-methoprene remained above 92% for four weeks. The reduction of attached ticks at 24 h on dogs treated with imidacloprid/permethrin did not reach 80% during the entire study. The number of ticks attached at 24 h was significantly (p<0.05) lower in the fipronil/amitraz/(S)-methoprene group than in the imidacloprid/permethrin group in assessments on Days 2, 15, 22, 29 and 36. When assessing efficacy based upon live ticks on treated versus control dogs, fipronil/amitraz/(S)-methoprene 24 h efficacy was above 95% for four weeks, decreasing to 77.8% at Day 36. The 24 h efficacy of imidacloprid/permethrin ranged from 56.2% to 86.7% through Day 29, never achieving 90% throughout the study. The 24-hour efficacy of fipronil/amitraz/(S)-methoprene was significantly (p<0.05) higher than imidacloprid/permethrin at all time points, including Day 36.     

Inhibitory effects of permethrin on flight responses,host‐searching,and foraging behaviour of Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of Plutella xylostella (Lepidoptera: Plutellidae)

Although it is well known that the application of broad‐spectrum synthetic insecticides reduces the effectiveness of natural enemies, the details of the actual mechanisms, including the lethal and sublethal effects of this reduction, are not fully understood. The inhibitory effects of a pyrethroid insecticide (permethrin), Adion 20% EC on the flight responses, host‐searching behaviour and foraging behaviour of Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), were investigated under laboratory conditions. In choice trials, the wasps showed significant preference for P. xylostella‐infested Komatsuna plants over insecticide‐treated plants, suggesting an inhibitory effect of the insecticide on the flight response of C. vestalis. When offered a pair of plants, the wasps showed a significant preference for P. xylostella‐infested plants compared to uninfested plants. However, significantly more wasps were attracted to infested permethrin‐treated plants than to uninfested plants, suggesting that the wasps are attracted to the volatile infochemicals from the infested plants, even if treated with permethrin. The searching time was significantly shorter and the mortality of C. vestalis adults on the insecticide‐treated plants significantly higher than in the control plants treated with distilled water. These results suggest that the application of the insecticide had an inhibitory effect on the wasps’‐searching behaviour and consequently reduced the effectiveness of C. vestalis as a biological control agent against P. xylostella. In addition, the strength of the inhibitory effect of permethrin on the attraction of the wasps to the plants is critical to the survival of C. vestalis. Our results suggest that the attraction of the wasps to the permethrin‐treated infested plants increases the risk of their exposure to this insecticide.     

水位变化影响蝌蚪存活、形态表型和植物血凝素反应

为探究黑斑侧褶蛙蝌蚪形态和生理特征对水位变化的响应,对480只大小相似的蝌蚪进行快速、中速和慢速干涸处理,统计各发育时期时长和存活率,测定变态完成后幼蛙的身体和内脏器官大小,以及对植物血凝素(PHA-P)的反应。结果表明: 对照组蝌蚪的变态时长最长,显著长于快速、中速和慢速干涸组;不同处理变态存活率在72.5%～90.8%,其中对照组最高,快速干涸组最低。对照和慢速干涸组幼蛙的体重和体长均显著高于中速和快速干涸组,快速干涸组体宽、体重与体长的比值、胴体湿重以及肺和脂肪体的湿重系数均最低,但心、脾、肾和消化器官的湿重系数和消化道各段的长度系数均无明显的组间差异。不同处理幼蛙对PHA-P的最大反应值均出现于注射后3 h,且中速和慢速干涸组的最大反应值均显著高于对照组,而快速干涸组与各组均无显著差异。表明黑斑侧褶蛙蝌蚪可通过加速变态发育进程来应对干旱胁迫,但会出现个体变小、细胞介导的免疫能力下降,不利于其成功登陆。     

Toxicity of pyrethroids and effect of synergists to larval and adult Helicoverpa zea, Spodoptera frugiperda, and Agrotis ipsilon (Lepidoptera: Noctuidae)

Based on 48 h LD50 estimates from topical bioassays, cypermethrin was more toxic than permethrin to Helicoverpa zea (Boddie) larvae and adults; however, the two pyrethroids did not differ significantly in their relative toxicities to Spodoptera frugiperda (J. E. Smith) and Agrotis ipsilon (Hufnagle). Larvae of each species generally were more susceptible to cypermethrin and permethrin than respective adults. The only exception to this generalization occurred with H. zea where slight overlap of the 95% confidence intervals with larvae and adult males was observed with cypermethrin. Respective males and females of the three species usually did not differ significantly in their susceptibility to either cypermethrin or to permethrin; however, with A. ipsilon, females were more susceptible to permethrin than to cypermethrin. Several instances of greater than additive toxicity were noted when insects were treated with piperonyl butoxide, S,S,S-tri-n-butyl phosphorotrithioate (DEF), or amitraz 30 min before cypermethrin. DEF exhibited the broadest spectrum of synergistic activity.     

Sublethal effects of neuroactive compounds on pheromone response thresholds in male oriental fruit moths

The pheromone-mediated flight behavior of male Oriental fruit moths in a sustained-flight tunnel was observed after males were treated topically with sublethal concentrations of permethrin, carbaryl, chlordimeform, dieldrin, octopamine, serotonin, yohimbine, and cyproheptadine. With the exception of serotonin all compounds were found to disrupt one or more specific elements of the male precopulatory flight sequence. Among the insecticides, dieldrin was least active, whereas permethrin, carbaryl, and chlordimeform induced unique effects at specific phases of the sequence. Octopamine induced a hypersensitivity to the olfactory signal and mimicked one of the effects observed with chlordimeform. Yohimbine and cyproheptadine significantly decreased moth activation to the chemical signal but did not alter flight performance in responding moths. Yohimbine and cyproheptadine also reversed the effects induced by octopamine. The results of our study show that the complex precopulatory sequence of behaviors exhibited by males is very sensitive to sublethal concentrations of a range of neuroactive compounds.     

Competing tadpoles: Australian native frogs affect invasive cane toads (Rhinella marina) in natural waterbodies

The cane toad (Rhinella marina) is one of the most successful invasive species worldwide, and has caused significant negative impacts on Australian fauna. Experimental work in the laboratory and in mesocosms has shown that tadpoles of native frogs can affect survival, size at metamorphosis and duration of larval period of cane toad tadpoles. To test if these effects occur in nature, we conducted a field experiment using two temporary ponds where we set up enclosures with tadpoles of native green tree frogs (Litoria caerulea) and cane toads in treatments with a range of densities and combinations. The presence of green tree frog tadpoles significantly decreased the growth rate of toad tadpoles and increased the duration of their larval period in both ponds; in one pond, frog tadpoles also significantly reduced the body length and mass of metamorph toads. Toad tadpoles did not have any significant negative effects on green tree frog tadpoles, but there was strong intraspecific competition within the latter species: increased frog tadpole density resulted in increased larval period and reduced survival, growth rate and size at metamorphosis for frogs at one or both ponds. Our results are encouraging for the possibility of using native frogs as one component of an integrated approach to the biological control of cane toads.     

Synergistic effect and field control efficacy of the binary mixture of permethrin and chlorpyrifos to brown planthopper (Nilaparvata lugens)

The brown Planthopper (BPH), Nilaparvata lugens is a major pest of rice production in tropical Asia. The appearance of insecticide resistance challenges the control of BPH in field. The development of new insecticide is expensive and time-consuming. Thus, the precise and proper use of existing compounds becomes an important issue in resistance management of this pest. In this study, five commercial insecticides of BPH (permethrin, chlorpyrifos, imidacloprid, clothianidin and thiamethoxam) were tested to explore the toxicity of the binary mixture between different kinds of insecticides. In all combinations of mixture, the mixtures of permethrin and chlorpyrifos displays synergistic effect at three different mixture ratios (1:1, 1:10 and 10:1). The strongest synergism observed in permethrin/ chlorpyrifos mixtures at 1:1 ratio (Combination index, CI = 0.39). Addition of enzyme inhibitor followed by detoxification enzyme activity assays suggested that the mechanism of synergistic effect of permethrin/chlorpyrifos mixture may result from inhibition of the cytochrome P450 monooxygenase and esterase activity. This inference can be supported through two lines of evidence. One is decrease of toxicity when permethrin/chlorpyrifos mixture in a 1:1 ratio plus triphenyl phosphate (TPP) or piperonyl butoxide (PBO), but increase of toxicity when permethrin/chlorpyrifos mixture in a 10:1 ratio plus TPP or PBO. Another is exposure of the 3rd instar nymphs to permethrin/chlorpyrifos mixture after 72 h also significantly decreased both cytochrome P450 monooxygenases and esterase activity. Further field trail showed the mixture of 50 ppm permethrin +50 ppm chlorpyrifos increased the field control efficiency significantly rather than permethrin alone or chlorpyrifos alone. Our study indicated that the mixture of permethrin and chlorpyrifos in a 1:1 ratio might be an effective method for the control of BPH in paddy field.     

Sublethal effects of permethrin on the chemical communication system of the pink bollworm moth,Pectinophora gossypiella

Topically applied sublethal doses of permethrin can interrupt chemical communication between the sexes of Pectinophora gossypiella by affecting both the signaler and the responder. The probability of calling by females is reduced when they are treated with doses of permethrin which are much less than the LD₅₀. Similarly, key stages in the behavioral response of males to sex pheromone are effectively blocked at these low doses. Males recover from these effects 4 days after treatment, but calling by females is still significantly reduced at this time. Chemical control of P. gossypiella populations with permethrin may not be limited to mortality, and potentially includes effective control of behavioral aspects of chemical communication.     

Leukocyte Nurr1 as peripheral biomarker of early-life environmental exposure to permethrin insecticide

The effect of a low dose of the insecticide permethrin administered during early-life was evaluated on leukocytes inflammation mediators on 300- and 500-day-old rats. Nurr1, NF-κB-p65, Nrf2, lipid peroxidation and GSH levels increased with age but compared to the control group, treatment with permethrin induced a significant increase only of Nurr1 and lipid peroxidation in oldest rats. TNF-α and Rantes increased, while IL-1β, IL-2, IL-13 decreased in oldest treated rats. The results propose Nurr1, TNF-α, Rantes, GSH and plasma lipid peroxidation as peripheral biomarkers for monitoring the impact of early-life environmental exposure to xenobiotics in old age.     

On the taxonomy of the genus Megadiaptomus Kiefer,including the description of a new species (Copepoda,Calanoida) from India

The insecticide permethrin (a synthetic pyrethroid) was applied into enclosures (1 m diameter and 3.5 m deep) placed in a pond. The chemical was rapidly removed from the water to the sediments. Daphnia rosea and its predator, Chaoborus flavicans were seriously affected by this application and disappeared from the enclosure. Acanthodiaptomus pacificus increased as Chaoborus decreased. Two species of Cladocera which had not been observed before the treatment, established their populations after 10 days, when Chaoborus had not recovered. Whereas Tropocyclops pracinus declined when permethrin was applied at 10 µg 1^–1, the number of rotifer Keratella valga increased, suggesting a close relationship between these two species.Photosynthesis and phytoplankton were not significantly affected by permethrin, except for Ceratium hirundinella. The dominance of Dinobryon divergens continued in the treated enclosures, whereas other flagellate species, Scenedesmus and Nitzschia occurred during the second half of the experiments in the control enclosure and pond.