Direct and indirect effects of fenoxycarb on freshwater systems dominated by Neocaridina palmata (Decapoda: Atyidae) and macrophyte Ceratophyllum demersum.

Few studies have been conducted with regard to the effects of insecticides on population dynamics of shrimps and associated groups such as macrophytes, phytoplankton, microorganisms etc. In the present study, effects of a single application of fenoxycarb were tested using indoor freshwater systems dominated by Neocaridina palmata and Ceratophyllum demersum (Dicotyledons: Ceratophyllales). The no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for the N. palmata, as scaled by liberated chitobiase, were 6.48 µg/L and 27.76 µg/L, and the dose-related effect lasted for 14 days. Results of principal components analysis (PCA) and that of principal response curves (PRC) method showed that the biomass of C. demersum and concentrations of chlorophyll-a were suppressed, while the concentrations of phycocyanin were promoted. Illumina high-throughput sequencing was adopted to determine the diversity of bacteria and fungi in the media. Result of PCA and PRC showed that the fenoxycarb promoted photosynthetic bacteria (e.g. Cyanobacteria and Rhodobacterales) and suppressed groups involved in nitrogen and sulfur the transformation (e.g. Flavobacterium, hgcI_clade, Cystobasidium, Rhodotorula and Rhizobiales). Promotion in pathogen such as Pseudomonas and Cercozoa and suppression in beneficial taxa such as Novosphingobium and Rhodotorula were also sighted. Result of study suggested a water quality deterioration due to fenoxycarb applications.

Cascading effects caused by fenoxycarb in freshwater systems dominated by Daphnia carinata and Dolerocypris sinensis.

To evaluate the aquatic hazards of the insect juvenile hormone analogue fenoxycarb, a single application (0, 48.8, 156.3, 500, 1600, and 5120 µg/L) of it was done in indoor freshwater systems dominated by Daphnia carinata (daphnid) and Dolerocypris sinensis (ostracoda). The responses of zooplankton (counted by abundance and the activity and immuno-reactive content of free N-Acetyl-ß-D-glucosaminidase (NAGase)), phytoplankton (counted by chlorophyll and phycocyanin), planktonic bacteria and fungi, and some water quality parameters were investigated in a period of 35 d. Results of the study showed that the ostracoda was more sensitive than daphnid, with time-weighted average (TWA)-based no observed effect concentrations (NOECs) to be 8.45 and 12.66 µg/L in systems without humic acid addition (HA-) and to be 6.37 and 9.54 µg/L in systems with humic acid addition (HA+). The duration of treatment-related effects in the ostracoda population was longer than the daphnid population (21 vs. 14 days). Besides, the data analysis indicated that the toxicity of fenoxycarb was significantly enhanced in the HA+ systems. Owing to the reduced grazing pressure, the concentrations of chlorophyll and phycocyanin increased in the two highest treatments. The increase in photosynthesis along with a reduced animal excretion led to an increase in pH and a decrease in nutrient contents. These changes seemed to have an effect on the microbial communities. For example, the abundances of some opportunistic pathogens of aquatic animals (e.g. Aeromonas and Cladosporium) and organic-pollutant-degrading microorganisms (e.g. Ancylobacter and Azospirillum) increased significantly in microbial communities, but the abundances of Pedobacter, Candidatus Planktoluna, and Rhodobacter (photosynthetic bacteria) markedly decreased. This study provides useful information to understand the ecotoxicological impacts of fenoxycarb at the population and community levels while integrating the effects of HA on toxicity.

Design, synthesis, insecticidal activity and molecular docking of doramectin derivatives.

A series of new doramectin derivatives containing carbamate, ester and sulfonate were synthesized, and their structures were characterized by 1H and 13C nuclear magnetic resonance (NMR) and high-resolution mass spectrum (HRMS). Their insecticidal activities against oriental armyworm, diamondback moth, and corn borer were evaluated and compared with the parent doramectin and commercial avermectins, metolcarb, fenpropathrin. Among all compounds, three compounds (3a, 3g and 3h) showed excellent insecticidal effect. In particular, compound 3g containing cyclopropyl carbamate against oriental armyworm, diamondback moth, and corn borer, exhibited the most promising insecticidal activity with the final mortality rate of 66.67%, 36.67%, 40.00% at the concentration of 12.5 mg/L, respectively. The LC50 values of 3g were 5.8859, 22.3214, and 22.0205 mg/L, showing 6.74, 2.23, 2.21-fold higher potency than parent doramectin (LC50 values of 39.6907, 49.7736, and 48.6129 mg/L) and 6.83, 1.93, 3.36-fold higher potency than commercial avermectins (LC50 values of 40.2489, 42.9922, and 73.9508 mg/L). Additionally, molecular docking simulations revealed that 3g displayed stronger hydrogen-bonding action in binding with the GABA receptor than parent doramectin, which were crucial for keeping high insecticidal activity. The present work demonstrated that these compounds containing alkyl carbamate group could be considered as potential candidates for the development of novel pesticides in the future.

Comparative ovarian microarray analysis of juvenile hormone-responsive genes in water flea Daphnia magna: potential targets for toxicity.

The freshwater zooplankton Daphnia magna has been extensively employed in chemical toxicity tests such as OECD Test Guidelines 202 and 211. Previously, it has been demonstrated that the treatment of juvenile hormones (JHs) or their analogues to female daphnids can induce male offspring production. Based on this finding, a rapid screening method for detection of chemicals with JH-activity was recently developed using adult D. magna. This screening system determines whether a chemical has JH-activity by investigating the male offspring inducibility. Although this is an efficient high-throughput short-term screening system, much remains to be discovered about JH-responsive pathways in the ovary, and whether different JH-activators act via the same mechanism. JH-responsive genes in the ovary including developing oocytes are still largely undescribed. Here, we conducted comparative microarray analyses using ovaries from Daphnia magna treated with fenoxycarb (Fx; artificial JH agonist) or methyl farnesoate (MF; a putative innate JH in daphnids) to elucidate responses to JH agonists in the ovary, including developing oocytes, at a JH-sensitive period for male sex determination. We demonstrate that induction of hemoglobin genes is a well-conserved response to JH even in the ovary, and a potential adverse effect of JH agonist is suppression of vitellogenin gene expression, that might cause reduction of offspring number. This is the first report demonstrating different transcriptomics profiles from MF and an artificial JH agonist in D. magna ovary, improving understanding the tissue-specific mode-of-action of JH. Copyright © 2016 John Wiley & Sons, Ltd.

Phenotypic defects in newborn Gammarus fossarum (Amphipoda) following embryonic exposure to fenoxycarb.

During morphogenesis numerous morphogenetic factors ensure the production of a target phenotype. By disrupting these processes, a toxic exposure during this period could cause an increase of phenotypic defects. In the present study, embryos of the freshwater amphipod Gammarus fossarum were exposed throughout the embryogenesis to increasing concentrations of fenoxycarb (0, 0.5µgL-1, 5µgL-1 and 50µgL-1), a growth regulator insecticide analog of the insect juvenile hormone. In addition, to identify morphogenesis' sensitive period, embryos were exposed during either early or late embryonic development to 5µgL-1 of fenoxycarb. In newborn individuals from exposed embryos, three phenotypes were investigated: i) eye pigmentation, ii) length of the antenna and gnathopod of both left and right sides and iii) midgut tissue state. Developmental homeostasis was assessed by measuring fluctuating asymmetry and inter-individual variance of both the antenna and gnathopod. Exposure to 5µgL-1 and 50µgL-1 fenoxycarb throughout the embryonic development induced a delayed hatching and altered appendages size. Moreover, exposure to 5µgL-1 throughout the embryogenesis and during the gastrulation phase impaired eye pigmentation, while exposure to 50µgL-1 resulted in increased tissue damages of the midgut. No significant increase of fluctuating asymmetry was observed in exposed individuals, neither for the antenna nor for the gnathopod. These results demonstrate that fenoxycarb can alter embryonic development of G. fossarum without disrupting developmental homeostasis.

Secondary biomarkers of insecticide-induced stress of honey bee colonies and their relevance for overwintering strength.

The evaluation of pesticide side-effects on honeybees is hampered by a lack of colony-level bioassays that not only are sensitive to physiological changes, but also allow predictions about the consequences of exposure for longer-term colony productivity and survival. Here we measured 28 biometrical, biochemical and behavioural indicators in a field study with 63 colonies and 3 apiaries. Colonies were stressed in early summer by feeding them for five days with either the carbamate growth regulator fenoxycarb or the neurotoxic neonicotinoid imidacloprid, or left untreated. Candidate stress indicators were measured 8-64 days later. We determined which of the indicators were influenced by the treatments, and which could be used as predictors in regression analyses of overwintering strength. Among the indicators influenced by fenoxycarb were the amount of brood in colonies as well as the learning performance and 24h-memory of bees, and the concentration of the brood food component 10HDA in head extracts. Imidacloprid significantly affected honey production, total number of bees and activity of the immune-related enzyme phenoloxidase in forager bee extracts. Indicators predictive of overwintering strength but unrelated to insecticide feeding included vitellogenin titer and glucose oxidase-activity in haemolymph/whole body-extracts of hive bees. Apart from variables that were themselves components of colony strength (numbers of bees/brood cells), the only indicator that was both influenced by an insecticide and predictive of overwintering strength was the concentration of 10HDA in worker bee heads. Our results show that physiological and biochemical bioassays can be used to study effects of insecticides at the colony level and assess the vitality of bee colonies. At the same time, most bioassays evaluated here appear of limited use for predicting pesticide effects on colony overwintering strength, because those that were sensitive to the insecticides were not identical with those that were predictive of colony overwintering. Our study therefore illustrates the difficulties involved in evaluating the economic/ecological significance of pesticide-induced stress in honey bee field studies.

Effects of an insect growth regulator and a solvent on honeybee (Apis mellifera L.) brood development and queen viability.

Honeybee toxicology is complex because effects on individual bees are modulated by social interactions between colony members. In the present study, we applied high doses of the insect growth regulator fenoxycarb to honeybee colonies to elucidate a possible interplay of individually- and colony-mediated effects regarding honey bee toxicology. Additionally, possible effects of the solvent dimethyl sulfoxide (DMSO) were assessed. We conducted studies on egg hatching and brood development to assess brood care by nurse bees as well as queen viability. Egg hatching was determined by the eclosion rate of larvae from eggs originating from colonies (i) treated with sugar syrup only, (ii) treated with sugar syrup containing DMSO and (iii) treated with sugar syrup containing fenoxycarb (dissolved in DMSO). To evaluate brood development, combs with freshly laid eggs were reciprocally transferred between colonies, and development of brood was examined in the recipient hive. Brood reared inside DMSO- and fenoxycarb-treated colonies as well as brood from DMSO- and from fenoxycarb-exposed queens showed higher mortality than brood not exposed to the chemicals. No differences were found in egg hatching among the treatments, but there was a higher variability of eclosion rates after queens were exposed to fenoxycarb. We also observed queen loss and absconding of whole colonies. Based on our results we infer that fenoxycarb has queen- as well as nurse bee-mediated effects on brood quality and development which can lead to the queen's death. There also is an effect of DMSO on the nurse bees' performance that could disturb the colony's equilibrium, at least for a delimited timespan.

Growth evaluation method by live imaging of Daphnia magna and its application to the estimation of an insect growth regulator.

The zooplankton Daphnia magna has been widely used as a test organism to assess the toxicity of chemical substances because of its important position in aquatic ecology and its ease of handling. Among the various endpoints for toxicity evaluation, growth rate is one of the most critical and many studies have been conducted. However, measurement f growth rate was time-consuming and not an ideal endpoint in terms of screening. In this study, we demonstrated a live imaging method to monitor the growth of daphnids by area measurement. In this method, daphnid images were directly obtained from a swimming chamber and these images were processed for the evaluation of growth. The reliability of this method was confirmed by comparison with the conventional dry weight method of the same animals. The body area of daphnids using this method showed a strong correlation with the dry weight method, with R(2) = 0.930. In addition, we quantified the effect of a toxicant, fenoxycarb, on the growth of the animal. Fenoxycarb concentrations of 0, 0.027,0.27 and 2.7 µg l(­1) were tested and their effects on growth were estimated by the live imaging method. In the toxicity test,the area of daphnids decreased significantly with increasing fenoxycarb concentration. These results indicate that the present live imaging method is a reliable approach for daphnid toxicity testing. This method is promising for high through put Daphnia toxicity tests and real-time individual observations.

Morphometric alterations, steatosis, fibrosis and active caspase-3 detection in carbamate bendiocarb treated rabbit liver.

Increasing use of pesticides all over the world makes it necessary to reveal the toxic risk in populations of nontargeted organisms. Bendiocarb is one of the 12 insecticides recommended by the World Health Organization for use in malaria control in Africa, and is used against a variety of insects. The liver has an important role in its process of detoxication and excretion. In our experiment 56 adult rabbits of breed HY+, 28 males and 28 females were used. Animals were divided into groups (control, days 10, 20, 30 of bendiocarb administration). The presence of many binucleated hepatocytes, the highest number of liver cells and their decreased size at 10 day after bendiocarb administration was observed as an evidence of the hepatic regeneration. After the long-term treatment pronounced changes were presented such as vacuolization and dilatation of hepatocytes, dilatation of sinusoids between hepatocytes, and focal infiltration of inflammatory cells. Numerous cells with caspase-3 activity were present throughout the organ, most commonly around the portal tract and close to the central vein. Short and long-term bendiocarb treatment showed the central vein thickened rim with increased deposition of collagen, spreading of collagen fibers into the perisinusoidal, and pericellular space surrounding the central veins, and septal fibrosis extended from the portal tract. Subsequently, presence of the lipid vacuoles both in the liver parenchyma and inner of the hepatocytes were observed. These results suggest that bendiocarb treatment leads to increased cell death, liver perisinusoidal fibrosis, and steatosis, especially during the long-term administration.

Characterization of the toxicological effects of aminocarb on rats: hematological, biochemical, and histological analyses.

Aminocarb is a widely applied carbamate insecticide with action of controlling pests such as Lepidoptera and Coleoptera. In this study, subchronic effects on Wistar rats were investigated using hematological, biochemical, and histological techniques. Rats were exposed orally at sublethal levels of 10, 20, or 40 mg/kg body weight (groups A, B, and C, respectively) for 14 d. Hematological results revealed no statistical differences after 1 d of exposure but significant reduction in white blood cells detected after 7 d of exposure in group C, as well as, in all treated groups after 14 d of exposure. Biochemical data showed a decrease of acetylcholinesterase activity in all groups after 1 d of exposure with a return to normal after 7 and 14 d. Significant increase in alkaline phosphatase activity of rats exposed to aminocarb was noted after 7 d of treatment. The levels of triglycerides were also significantly decreased. The present investigation also showed a significant increase in content of serum urea and creatinine in animals from group A (14 d), and from groups B and C (7 and 14 d). Histological results demonstrated hemorrhagic focus on hepatic and renal parenchyma in all exposed groups. Taken together, the attained results were dose dependent and indicated adverse effects of aminocarb on hepatic and renal functions, as well as on immune responsiveness at sublethal tested doses.

Molecular impact of juvenile hormone agonists on neonatal Daphnia magna.

Daphnia magna has been used extensively to evaluate organism- and population-level responses to pollutants in acute toxicity and reproductive toxicity tests. We have previously reported that exposure to juvenile hormone (JH) agonists results in a reduction of reproductive function and production of male offspring in a cyclic parthenogenesis, D. magna. Recent advances in molecular techniques have provided tools to understand better the responses to pollutants in aquatic organisms, including D. magna. DNA microarray was used to evaluate gene expression profiles of neonatal daphnids exposed to JH agonists: methoprene (125, 250 and 500 ppb), fenoxycarb (0.5, 1 and 2 ppb) and epofenonane (50, 100 and 200 ppb). Exposure to these JH analogs resulted in chemical-specific patterns of gene expression. The heat map analyses based on hierarchical clustering revealed a similar pattern between treatments with a high dose of methoprene and with epofenonane. In contrast, treatment with low to middle doses of methoprene resulted in similar profiles to fenoxycarb treatments. Hemoglobin and JH epoxide hydrolase genes were clustered as JH-responsive genes. These data suggest that fenoxycarb has high activity as a JH agonist, methoprene shows high toxicity and epofenonane works through a different mechanism compared with other JH analogs, agreeing with data of previously reported toxicity tests. In conclusion, D. magna DNA microarray is useful for the classification of JH analogs and identification of JH-responsive genes.

Ultrastructural changes in the rabbit liver induced by carbamate insecticide bendiocarb.

Carbamates (CB) are used as insecticides and some of them have been registered as human drugs. The mechanism of CB poisoning involves reversible inhibition of acetylcholine esterase. In the present study, we investigated changes in liver ultrastructure in rabbits (Oryctolagus cuniculus) which were administered bendiocarb for 3, 10, 20, and 30 days. Rabbits in all experimental groups received capsules of bendiocarb (96% Bendiocarb, Bayer, Germany) per os daily at a dose of 5 mg/kg of body weight, and after day 11 received the same dose every 48 h. The observed changes were only moderate, focal, and the effect on the liver was not uniform. On the third day of the experiment, injured hepatocytes had dilated bile capillaries with reduced microvilli. There were no visible alterations in the intercellular contacts. Nuclei of these cells were irregular in shape. Many hepatocytes showed considerable increase in the number of peroxisomes. On day 10 of the experiment, the number of peroxisomes was reduced. Other changes, such as dilated rough endoplasmic reticulum and proliferation of smooth endoplasmic reticulum were observed on day 20. The number of lipid droplets in hepatocytes gradually increased. Usually they were present in low numbers, but on day 30 of the experiment their number increased significantly. They coalesced and formed a single lipid droplet which changed the shape of the nuclei. The results presented in this study indicate that both short and long-term administration of bendiocarb affects the liver ultrastructure. At the same time we also observed rapid onset of regeneration of the damaged tissue through activation of hepatocytes and oval cells.

Pesticide exposure impacts not only hatching of dormant eggs, but also hatchling survival and performance in the water flea Daphnia magna.

Laboratory ecotoxicity tests and biomonitoring in aquatic systems are currently based on the active component of invertebrate communities. Even though dormant egg banks are crucial for the long term survival and community dynamics of many aquatic organisms, the effects of anthropogenic activities on dormant egg bank dynamics have rarely been studied. In this study we investigated the effects of two pesticides with a different mode of action (carbaryl and fenoxycarb) on hatching of Daphnia magna dormant eggs (ephippia) as well as on survival, growth and reproduction of the hatched neonates. Dormant eggs were exposed to the pesticides simultaneously to incubation under conditions that induce hatching (long daylight and 20 °C). Carbaryl had no negative effects on embryonic development or hatching rate up to concentrations almost 1,000 times the median effect concentration (EC50) of neonate survival in acute tests. Fenoxycarb, however, had a significant dose-related effect by delaying or completely stopping the hatching process and caused severe abnormalities in developing individuals. Both pesticides had significant negative effects on survival and reproduction of the hatchlings. These results indicate that, in addition to inducing mortality of active individuals, pesticides can affect zooplankton communities by altering hatching dynamics and life history traits of hatched individuals. We briefly discuss how such pollution induced changes in the benthic-pelagic coupling could translate into trans-generational effects impacting ecological and evolutionary dynamics.

Population growth rate responses of Ceriodaphnia dubia to ternary mixtures of specific acting chemicals: pharmacological versus ecotoxicological modes of action.

When considering joint toxic apical effects at higher levels of biological organization, such as the growth of populations, the so-called pharmacological mode of action that relies on toxicological mechanistic effects on molecular target sites may not be relevant. Such effects on population growth rate will depend on the extent to which juvenile and adult survival rates and production rates (juvenile developmental rates and reproduction) are affected by toxic exposure and also by the sensitivity of population growth rates to life-history changes. In such cases, the ecotoxicological mode of action, defined as the crucial life-history trait processes and/or xenobiotic-life-history trait interactions underlying a toxicological effect on population growth rate, should be considered. Life-table response experiments with the crustacean Ceriodaphnia dubia exposed to single and ternary mixtures of nine compounds were conducted to test the hypothesis that joint effects on population growth rates could be predicted from the mixture constituent ecotoxicological mode of action. Joint effects of mixtures containing pharmacologically dissimilar compounds (cadmium, λ-cyhalothrin, and chlorpyrifos) that differentially affected life-history traits contributing to population growth rates were accurately predicted by the independent-action concept. Conversely, the concentration-addition concept accurately predicted joint effects of two different mixtures: one containing pharmacologically similar acting pyrethroids that also affected similarly life-history traits, the other one that included pharmacologically dissimilar compounds (3,4-dichloroaniline, sodium bromide, and fenoxycarb) acting mainly on reproduction rates. These results indicate that when assessing combined effects on population growth rate responses, selection of mixture toxicity conceptual models based on the ecotoxicological mode of action of mixture constituents provided more accurate predictions than those based on the pharmacological mode of action.

Chick development and high dose of bendiocarb.

Developmental data of carbamate pesticides are scarce although they generally possess low toxicity for vertebrates. The aim of the study was to investigate the toxicity of bendiocarb to liver and central nervous system of chick embryos. Bendiocarb (1600 µg/egg) was administered to the embryo through membrana papyracea on embryonic day 3 and 10. In the liver and central nervous system we observed no macroscopic or microscopic changes. These organs were also investigated for caspase activity in regard to application of bendiocarb and no differences in the caspase immunopositivity were observed in comparison with the control. The embryolethality after bendiocarb respective dose was high (94 %) on the embryonic day 3, though following results indicated no toxicity to investigated organs and no increase in the number of apoptotic cells in survived chick embryos on both the early (day 3 of incubation) and the later (day 10 of incubation) developmental stage.

In vivo and in vitro effect of bendiocarb on rabbit testicular structure and spermatozoa motility.

In this study the effect of bendiocarb on the rabbit testicular structure and spermatozoa motility was investigated. For testicular structure evaluation the animals were fed with bendiocarb tablets daily at a dose of 5 mg/kg of body weight for 13 days. The relative volume of the germinal epithelium, interstitium and lumen was measured. The testicular structure evaluation showed decreased relative volume of germinal epithelium in both experimental groups in comparison with the control group. The relative volume of the interstitium was increased in both experimental groups. An increase of the relative volume of the lumen was registered also in both experimental groups. Qualitative analysis detected a dilatation of blood vessels in the interstitium, undulation of the basal membrane and some empty spaces in the germinal epithelium after bendiocarb administration. The spermatozoa motility was evaluated by the computer assisted semen analyzer (CASA) method in various time intervals (0-180 minutes) and the bendiocarb concentration in the culture medium added to experimental groups varied from 0.054 to 0.268 mg/mL. Spermatozoa motility and progressive motility significantly decreased with increased bendiocarb administration and with extending the period of incubation. For other fine motility parameters, a decrease dependent on the time of incubation and on the bendiocarb concentration almost in all experimental groups in comparison to the control was detected. These results clearly suggest that in vitro also in vivo bendiocarb administration decrease male fertility.

Evaluation of bendiocarb cytotoxicity in mammalian and insect cell cultures.

There is an increasing need for rapid and easily interpreted in vitro assays to screen for possible cytotoxicity of pesticides. The objective of this study was to investigate the effect of the carbamate insecticide bendiocarb on mammalian and insect cell cultures. The cytotoxicity of this insecticide was evaluated by cell proliferation and cellular damage was assessed by evaluation of the cytopathic effect and lactate dehydrogenase (LDH) leakage. Cells of insect origin (Sf21) were the most sensitive to bendiocarb with significant (P < 0.01) suppression of their proliferative activity ranging from 10(-1)-10(-5) M. However, significant suppression of proliferative activity was also recorded in rat liver cells (WBF344; 10(-1)-10(-3) M; P < 0.01-0.05) and rabbit kidney cells (RK13; 10(-1) M; P < 0.01). In contrast with the proliferation activity of cells, a cytopathic effect based on cellular damage and LDH leakage into the medium was observed only at the highest concentration (10(-1) M) in RK 13 and WBF344 cells, but not in the Sf21 insect cell line. Our results indicate that bendiocarb exposure caused a cell-type dependent decrease in cell proliferation; however, cell damage and LDH leakage into the medium were not present or were strongly limited, dependent on the cell phenotype. Cell proliferation was shown as a sensitive indicator for evaluation of the cytotoxic effect of bendiocarb in vitro; on the other hand, microscopic signs of cellular damage and LDH leakage were insufficient in vitro markers.

Determination of mRNA expression of DMRT93B, vitellogenin, and cuticle 12 in Daphnia magna and their biomarker potential for endocrine disruption.

We explored the use of molecular genetic biomarkers for endocrine disruption in Daphnia magna after the exposure to fenoxycarb (FOC), a model juvenile hormone analog. For this purpose, the mRNA expression patterns of DMRT93B (DMRT, sex determination), cuticle 12 (CUT, molting), and vitellogenin (VTG, embryo development) were determined in D. magna. Furthermore, these results were compared with developmental abnormality and reproduction performance. The fold changes of CUT and VTG mRNA expression showed significant dose-response relationship with FOC exposure. Relative mRNA expressions of DMRT and CUT showed notable changes at as low as 1 ng/l FOC. After chronic exposure FOC significantly delayed the first day of reproduction and decreased the number of young and growth rate even at 10 ng/l FOC. A concentration-dependant trend in reproduction effect was also observed. Developmental abnormality such as poorly developed second antennae and curved or unextended shell spines were observed. These results suggest that the three mRNAs, i.e., DMRT, CUT, and VTG can be used as biomarkers of endocrine disrupting effects in D. magna.

Ultraviolet radiation increases sensitivity to pesticides: synergistic effects on population growth rate of Daphnia magna at low concentrations.

In the present study we aimed to investigate whether UV-B radiation can exacerbate effects of pesticides fenoxycarb, pirimicarb, and tebufenpyrad on the survival, reproduction, and population growth rate of the standard test species Daphnia magna. We applied sublethal pesticides' concentrations and UV doses and observed no effects on survival. However, we observed synergistic effects of UV and pesticides on both cumulative reproduction and population growth rate (21 days) for fenoxycarb (100 µg/L) and pirimicarb (10 µg/L), but a less-than-additive effect for tebufenpyrad (5-10 µg/L). In the series exposed to UV and fenoxycarb or pirimicarb, the population growth rate dropped down to 0.1, while in the control series it was around 0.3. The results indicate that concentrations of some toxicants that are nontoxic in standard tests can cause harmful population-level effects when combined with UV.

Efficacy of biorational insecticides against Bemisia tabaci (Genn.) and their selectivity for its parasitoid Encarsia formosa Gahan on Bt cotton.

The toxicity of seven biorational insecticides [five insect growth regulators (Buprofezin, Fenoxycarb, Pyriproxyfen, Methoxyfenozide, and Tebufenozide) and two oil-extracts of neem and bitter gourd seeds] against Bemisia tabaci and their selectivity for its parasitoid, Encarsia formosa were evaluated in laboratory and field conditions for 2 years (2018-2019) in Pakistan. Toxicity results demonstrate that Pyriproxyfen, Buprofezin, and Fenoxycarb proved to be effective (80-91% mortality and 66.3-84.2% population-reduction) against B. tabaci followed by Methoxyfenozide, Tebufenozide (50-75% mortality and 47.8-52.4% population-reduction), and then oil-extracts of neem and bitter gourd (25-50% mortality and 36.5-39.8% population-reduction) in the laboratory [72 h post-application exposure interval (PAEI)] and field trails (168 h PAEI), respectively. All tested biorationals, except Methoxyfenozide [(slightly-harmful/Class-II), i.e., causing mortality of parasitoids between a range of 25-50%] and Tebufenozide [(moderately-harmful/Class-III), i.e., causing mortality of parasitoids between the ranges of 51-75%], proved harmless/Class-I biorationals at PAEI of 7-days in the field (parasitism-reduction < 25%) and 3-days in the lab (effect < 30%). In laboratory bioassays, exposure of parasitized-pseudopupae and adult-parasitoids to neem and bitter gourd oils demonstrated that these compounds proved harmless/Class-I biorationals (< 30% mortality). Alternatively, Pyriproxyfen, Buprofezin, Fenoxycarb, Methoxyfenozide, and Tebufenozide were slightly-harmful biorationals (30-79% mortality) against the respective stages of E. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful to E. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) of B. tabaci.