Neonicotinoid pesticides can reduce honeybee colony genetic diversity

Sublethal acetamiprid exposure induces immunity, suppresses pathways linked to juvenile hormone synthesis in queens and affects cycle-related signaling in emerging bees

Acetamiprid is the only neonicotinoid registered in the European Union because the risks of neonicotinoids to honey bees and other pollinators are strictly regulated. Herein, we orally exposed honey bee colonies to sublethal concentrations of acetamiprid (20 μg/L) under isolated conditions. After one month of continuous exposure, the emerging bees and queens were collected and analyzed via high-throughput label-free quantitative proteomics using a data-independent acquisition strategy. Six and 34 significantly differentially expressed proteins (DEPs) were identified in the emerging bees and queens, respectively. Mrjp3 was the only DEP found in both sample types/castes, and its opposite regulation illustrated a differential response. The DEPs in the emerging bees (H/ACA RNP, Rap1GAP, Mrjp3, and JHE) suggested that sublethal exposure to acetamiprid affected cell cycle-related signaling, which may affect the life history of workers in the colony. The DEPs with increased levels in queens, such as Mrjps 1-4 and 6-7, hymenoptaecin, and apidaecin 22, indicated an activated immune response. Additionally, the level of farnesyl pyrophosphate synthase (FPPS), which is essential for the mevalonate pathway and juvenile hormone biosynthesis, was significantly decreased in queens. The impaired utilization of juvenile hormone in queens supported the identification of additional DEPs. Furthermore, the proteome changes suggested the existence of increased neonicotinoid detoxification by UDP-glucuronosyltransferase and increased amino acid metabolism. The results suggest that the continuous exposure of bee colonies to acetamiprid at low doses (nanograms per gram in feed) may pose a threat to the colonies. The different exposure routes and durations for the emerging bees and queens in our experiment must be considered, i.e., the emerging bees were exposed as larvae via feeding royal jelly and beebread provided by workers (nurse bees), whereas the queens were fed royal jelly throughout the experiment. The biological consequences of the proteomic changes resulting from sublethal/chronic exposure require future determination.

Neonicotinoid exposure increases Varroa destructor (Mesostigmata: Varroidae) mite parasitism severity in honey bee colonies and is not mitigated by increased colony genetic diversity

Agrochemical exposure is a major contributor to ecological declines worldwide, including the loss of crucial pollinator species. In addition to direct toxicity, field-relevant doses of pesticides can increase species' vulnerabilities to other stressors, including parasites. Experimental field demonstrations of potential interactive effects of pesticides and additional stressors are rare, as are tests of mechanisms via which pollinators tolerate pesticides. Here, we controlled honey bee colony exposure to field-relevant concentrations of 2 neonicotinoid insecticides (clothianidin and thiamethoxam) in pollen and simultaneously manipulated intracolony genetic heterogeneity. We showed that exposure increased rates of Varroa destructor (Anderson and Trueman) parasitism and that while increased genetic heterogeneity overall improved survivability, it did not reduce the negative effect size of neonicotinoid exposure. This study is, to our knowledge, the first experimental field demonstration of how neonicotinoid exposure can increase V. destructor populations in honey bees and also demonstrates that colony genetic diversity cannot mitigate the effects of neonicotinoid pesticides.

Novel insights into paternity skew in a polyandrous social wasp

Females of many species are polyandrous. However, polyandry can give rise to conflict among individuals within families. We examined the level of polyandry and paternity skew in the common eastern yellowjacket wasp, Vespula maculifrons, in order to gain a greater understanding of conflict in social insects. We collected 10 colonies of V. maculifrons and genotyped workers and prereproductive queens at highly variable microsatellite markers to assign each to a patriline. Genotypic data revealed evidence of significant paternity skew among patrilines. In addition, we found that patrilines contributed differentially to caste production (worker vs. queen), suggesting an important role for reproductive conflict not previously discovered. We also investigated if patterns of paternity skew and mate number varied over time. However, we found no evidence of changes in levels of polyandry when compared to historical data dating back almost 40 years. Finally, we measured a suite of morphological traits in individuals from the most common and least common patrilines in each colony to test if males that showed highly skewed reproductive success also produced offspring that differed in phenotype. Our data revealed weak correlation between paternity skew and morphological phenotype of offspring sired by different males, suggesting no evidence of evolutionary tradeoffs at the level investigated. Overall, this study is the first to report significant paternity and caste-associated skew in V. maculifrons, and to investigate the phenotypic consequences of skew in a social wasp. Our results suggest that polyandry can have important consequences on the genetic and social structure of insect societies.

Re-using food resources from failed honey bee (Apis mellifera L.) colonies and their impact on colony queen rearing capacity

For over a decade, beekeepers have experienced high losses of honey bee (Apis mellifera L.) colonies due to a variety of stressors including pesticide exposure. Some of these chemical stressors may residually remain in the colony comb and food resources (pollen and nectar) of failed colonies and be later re-used by beekeepers when splitting and building back new colonies. The practice of re-using comb from previously perished colonies (termed "deadout") is common in beekeeping practice, but its role in affecting colony health is not well understood. Here, we evaluate the impact of reused, pesticide-contaminated "deadout" combs on colony function during the process of replacing a queen bee. Queenless microcolonies were established to monitor queen rearing capacity in two treatment groups: (1) colonies given frames containing food resources from deadout colonies in control "clean" apiaries and, (2) colonies given frames containing "contaminated" resources from deadout colonies originating from apiaries experiencing chronic pesticide exposure from widespread systemic pesticide pollution (including neonicotinoid insecticides: clothianidin and thiamethoxam). Results indicate that colonies given pesticide-contaminated resources produced fewer queen cells per colony and had a lower proportion of colonies successfully raising a functional, diploid egg-laying queen. This research highlights the deleterious effects of re-using deadout combs from colonies previously lost due to pesticide contamination.

Contamination of Honeybee (Apis mellifera L.) Royal Jelly by Pesticides and Sample Preparation Methods for Its Determination: A Critical Appraisal

Pesticides can easily enter the food chain, harming bee populations and ecosystems. Exposure of beehive products to various contaminants has been identified as one of the factors contributing to the decline in bee populations, and multiple food alerts have been reported. Despite this fact, royal jelly, a valuable bee product with nutritional and functional properties, has received less attention in this context. Pesticide residues of different chemical class can contaminate royal jelly when foraging bees collect pollen or nectar from pesticide-treated flowers, or in some cases, due to its frequent and inappropriate use in the treatment of mites in beehives. To monitor this issue and also make it more reliable, it is crucial to develop effective sample preparation methods for extracting pesticides from royal jelly for subsequent analysis. In this context, this review provides information about sample preparation methods (solid-phase extraction, solvent extraction, and QuEChERS-quick, easy, cheap, effective, rugged and safe) and analytical methods that have been validated or improved to extract and analyze pesticides, respectively, in royal jelly samples of different origins. Finally, future perspectives are discussed. With this background, we aim to provide data that can guide future research related to this topic.

Screening and identification of a DNA aptamer to construct the label-free fluorescent aptasensor for ultrasensitive and selective detection of clothianidin residue in agricultural products

Clothianidin pesticide not only pollutes the ecological environment, but also poses a potential threat to human health. Thus, it is of great importance to develop efficient and accurate methods to recognize and detect clothianidin residues in agricultural products. Aptamer has the advantages of easy modification, high affinity and good stability, which is particularly suitable as a recognition biomolecule for pesticide detection. However, the aptamer against clothianidin has not been reported. Herein, the aptamer (named CLO-1) had good selectivity and strong affinity (K_d = 40.66 ± 3.47 nM) to clothianidin pesticide, which was screened for the first time by Capture-SELEX strategy. The binding effect of CLO-1 aptamer to clothianidin was further studied by circular dichroism (CD) spectroscopy and molecular docking technique. Finally, the CLO-1 aptamer was used as the recognition molecule to construct a label-free fluorescent aptasensor using GeneGreen dye as sensing signal for the highly sensitive detection of clothianidin pesticide. The constructed fluorescent aptasensor had the limit of detection (LOD) as low as 5.527 μg L^-1 for clothianidin, and displayed good selectivity against other competitive pesticides. The aptasensor was applied to detect the clothianidin spiked in tomatoes, pears and cabbages, and the recovery rate was good in the range of 81.99%-106.64%. This study provides a good application prospect for the recognition and detection of clothianidin.

Honeybee queen exposure to a widely used fungicide disrupts reproduction and colony dynamic

Pollinators have to cope with a wide range of stressful, not necessarily lethal factors limiting their performance and the ecological services they provide. Among these stressors are pesticides, chemicals that are originally designed to target crop-harming organisms but that also disrupt various functions in pollinators, including flight, communication, orientation and memory. Although all these functions are crucial for reproductive individuals when searching for mates or nesting places, it remains poorly understood how pesticides affect reproduction in pollinators. In this study, we investigated how a widely used fungicide, boscalid, affects reproduction in honey bees (Apis mellifera), an eusocial insect in which a single individual, the queen, fulfills the reproductive functions of the whole colony. Boscalid is a succinate dehydrogenase inhibitor (SDHI) fungicide mainly used on rapeseed flowers to target mitochondrial respiration in fungi but it is also suspected to disrupt foraging-linked functions in bees. We found that immature queen exposure to sublethal, field relevant doses of boscalid disrupted reproduction, as indicated by a dramatic increase in queen mortality during and shortly after the nuptial flights period and a decreased number of spermatozoa stored in the spermatheca of surviving queens. However, we did not observe a decreased paternity frequency in exposed queens that successfully established a colony. Queen exposure to boscalid had detrimental consequences on the colonies they later established regarding brood production, Varroa destructor infection and pollen storage but not nectar storage and population size. These perturbations at the colony-level correspond to nutritional stress conditions, and may have resulted from queen reduced energy provisioning to the eggs. Accordingly, we found that exposed queens had decreased gene expression levels of vitellogenin, a protein involved in egg-yolk formation. Overall, our results indicate that boscalid decreases honey bee queen reproductive quality, thus supporting the need to include reproduction in the traits measured during pesticide risk assessment procedures.

Impacts of Ecological Shading by Roadside Trees on Tea Foliar Nutritional and Bioactive Components, Community Diversity of Insects and Soil Microbes in Tea Plantation

Roadside trees not only add aesthetic appeal to tea plantations, but also serve important ecological purposes for the shaded tea plants. In this study, we selected tea orchards with two access roads, from east to west (EW-road) and from south to north (SN-road), and the roadside trees formed three types of ecological shading of the adjoining tea plants; i.e., south shading (SS) by the roadside trees on the EW-road, and east shading and west shading (ES and WS) by the roadside trees on the SN-road. We studied the impacts of ecological shading by roadside trees on the tea plants, insects, and soil microbes in the tea plantation, by measuring the contents of soluble nutrients, bioactive compounds in the tea, and tea quality indices; and by investigating the population occurrence of key species of insects and calculating insect community indexes, while simultaneously assaying the soil microbiome. The results vividly demonstrated that the shading formed by roadside tree lines on the surrounding tea plantation (SS, ES, and WS) had adverse effects on the concentration of tea soluble sugars but enhanced the foliar contents of bioactive components and improved the overall tea quality, in contrast to the no-shading control tea plants. In addition, the roadside tree lines seemed to be beneficial for the tea plantation, as they reduced pest occurrence, and ES shading enhanced the microbial soil diversity in the rhizosphere of the tea plants.

Imidacloprid Induces Histopathological Damage in the Midgut, Ovary, and Spermathecal Stored Spermatozoa of Queens After Chronic Colony Exposure

Bee colony health is declining as a result of several factors, including exposure to pesticides. The development and strength of honey bee colonies depend on the reproductive success of queen bees. Because flowers are sources of food for bees, foragers can accidentally collect and carry contaminated pollen and nectar to their hives; and this may compromise the longevity and the life span of individuals. Thus, the present study aimed to observe the action of imidacloprid in the midgut and ovaries of Apis mellifera queens, as well as the effects on sperm stored in their spermatheca. To this end, the apiary was divided into three experimental groups: control, commercial imidacloprid, and active ingredient imidacloprid. For toxicity assays, a sucrose solution containing 1 µg/L of imidacloprid was offered to the colonies for 42 days. A control group received only food in the same period. In both treatments with imidacloprid, the midgut of queens showed modifications in the external musculature and cellular alterations. Such changes could lead to the nonrecovery of the epithelium and subsequently malabsorption of nutrients. Moreover, the digestive cells of queen bees exposed to the commercial imidacloprid presented pyknotic nuclei, suggesting a cell death process. The main alterations observed in the ovaries of these reproductive bees treated with commercial imidacloprid were degeneration and resorption of the ovariole content, which probably affected their fertilization and colony development. There were no significant changes in the spermatozoa morphology for both treatments with imidacloprid, but this insecticide may interfere with the development and reproductive success of A. mellifera colonies because it affects the morphology and function of essential organs for the survival of queens. Environ Toxicol Chem 2022;41:1637-1648. SETAC.

Pesticide residues in beebread and honey in Apis cerana cerana and their hazards to honey bees and human

The residue of pesticides in bee products such as beebread and honey threaten the survival of pollinators and human health. Apis cerana cerana is one of the leading managed honey bees in China. However, little is known about the residues of pesticides in hive products of A. c. cerana in China. Here, we investigated the pesticide residues in beebread and honey. The risk of detected residues of pesticides to honey bees was evaluated with hazard quotient (HQ) and BeeREX. Furthermore, we assessed the chronic and acute risks to humans according to the dietary exposure. Our results suggest that the pesticide residues detection ratio (25.4% for beebread and 2.8% for honey) and the concentrations of these residues is lower than previously reported. Additional risk assessments indicate that the residue levels of pesticides in tested honey of A. c. cerana do not pose a risk for human consumers. Among all identified pesticides, only thiamethoxam raises the concern for further risk assessment in the risk evaluation of honey bee colonies and thiamethoxam was safe for colonies in higer tier studies.

Thiamethoxam as an inadvertent anti-aphrodisiac in male bees

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There is consensus that neonicotinoids can impact non-target animal fertility.

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Thiamethoxam reduced both mating success and sperm physiology in bumblebees.

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Queens mated by exposed males had 50% less total living sperm in their spermatheca.

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Thiamethoxam may act as anti-aphrodisiac, thereby limiting conservation efforts.

Sexual reproduction is common to almost all multi-cellular organisms and can be compromised by environmental pollution, thereby affecting entire populations. Even though there is consensus that neonicotinoid insecticides can impact non-target animal fertility, their possible impact on male mating success is currently unknown in bees. Here, we show that sublethal exposure to a neonicotinoid significantly reduces both mating success and sperm traits of male bumblebees. Sexually mature male Bombus terrestris exposed to a field-realistic concentration of thiamethoxam (20 ng g⁻¹) or not (controls) were mated with virgin gynes in the laboratory. The results confirm sublethal negative effects of thiamethoxam on sperm quantity and viability. While the latency to mate was reduced, mating success was significantly impaired in thiamethoxam-exposed males by 32% probably due to female choice. Gynes mated by exposed males revealed impaired sperm traits compared to their respective controls, which may lead to severe constraints for colony fitness. Our laboratory findings demonstrate for the first time that neonicotinoid insecticides can negatively affect male mating success in bees. Given that holds true for the field, this provides a plausible mechanism contributing to declines of wild bee populations globally. The widespread prophylactic use of neonicotinoids may therefore have previously overlooked inadvertent anti-aphrodisiac effects on non-target animals, thereby limiting conservation efforts.

Chronic Effects of Imidacloprid on Honey Bee Worker Development-Molecular Pathway Perspectives

Sublethal dosages of imidacloprid cause long-term destructive effects on honey bees at the individual and colony levels. In this review, the molecular effects of sublethal imidacloprid were integrated and reported. Several general effects have been observed among different reports using different approaches. Quantitative PCR approaches revealed that imidacloprid treatments during the adult stage are expressed as changes in immuneresponse, detoxification, and oxidation-reduction response in both workers and queens. In addition, transcriptomic approaches suggested that phototransduction, behavior, and somatic muscle development also were affected. Although worker larvae show a higher tolerance to imidacloprid than adults, molecular evidence reveals its potential impacts. Sublethal imidacloprid treatment during the larval stage causes gene expression changes in larvae, pupae, and adults. Transcriptome profiles suggest that the population and functions of affected differentially expressed genes, DEGs, vary among different worker ages. Furthermore, an early transcriptomic switch from nurse bees to foragers was observed, suggesting that precocious foraging activity may occur. This report comprehensively describes the molecular effects of sublethal dosages of imidacloprid on the honey bee Apis mellifera. The corresponding molecular pathways for physiological and neurological responses in imidacloprid-exposed honey bees were validated. Transcriptomic evidence suggests a global and sustained sublethal impact of imidacloprid on honey bee development.

Effects of Insecticides and Microbiological Contaminants on Apis mellifera Health

Over the past two decades, there has been an alarming decline in the number of honey bee colonies. This phenomenon is called Colony Collapse Disorder (CCD). Bee products play a significant role in human life and have a huge impact on agriculture, therefore bees are an economically important species. Honey has found its healing application in various sectors of human life, as well as other bee products such as royal jelly, propolis, and bee pollen. There are many putative factors of CCD, such as air pollution, GMO, viruses, or predators (such as wasps and hornets). It is, however, believed that pesticides and microorganisms play a huge role in the mass extinction of bee colonies. Insecticides are chemicals that are dangerous to both humans and the environment. They can cause enormous damage to bees' nervous system and permanently weaken their immune system, making them vulnerable to other factors. Some of the insecticides that negatively affect bees are, for example, neonicotinoids, coumaphos, and chlorpyrifos. Microorganisms can cause various diseases in bees, weakening the health of the colony and often resulting in its extinction. Infection with microorganisms may result in the need to dispose of the entire hive to prevent the spread of pathogens to other hives. Many aspects of the impact of pesticides and microorganisms on bees are still unclear. The need to deepen knowledge in this matter is crucial, bearing in mind how important these animals are for human life.

Reproductive fitness of honey bee queens exposed to thiamethoxam during development

The productivity and survival of honey bee (Apis mellifera) colonies depend on queen bee health. Colony-level neonicotinoid exposure has negative effects on reproductive fitness of honey bee queens. However, it is unclear if the observed effects are a direct outcome of neonicotinoid toxicity or result from suboptimal care of developing queens by exposed workers. The aim of this study was to evaluate larval survival, reproductive fitness, and histopathology of honey bee queens exposed to incremental doses (0, 5, 50 ng) of the neonicotinoid thiamethoxam (THI) applied directly to individual late larvae (7 days post-oviposition) of queens. The 5 ng dose represents a calculated high environmental level of exposure for honey bee queen larvae. Morphometric evaluation revealed that the total area of mandibular gland epithelium in queens exposed to 5 and 50 ng THI was reduced by 14% (P = .12) and 25% (P = .001), respectively. Decreased mandibular gland size may alter pheromone production, which could in part explain previously observed negative effects of THI on the reproductive fitness of queens. We also found that late larval exposure to THI reduced larval and pupal survival and decreased sperm viability in mated queens. These changes may interfere with queen development and reproductive longevity.

Effects of developmental exposure to pesticides in wax and pollen on honey bee (Apis mellifera) queen reproductive phenotypes

Stressful conditions during development can have sub-lethal consequences on organisms aside from mortality. Using previously reported in-hive residues from commercial colonies, we examined how multi-pesticide exposure can influence honey bee (Apis mellifera) queen health. We reared queens in beeswax cups with or without a pesticide treatment within colonies exposed to treated or untreated pollen supplement. Following rearing, queens were open-mated and then placed into standard hive equipment in an "artificial swarm" to measure subsequent colony growth. Our treated wax had a pesticide Hazard Quotient comparable to the average in beeswax from commercial colonies, and it had no measurable effects on queen phenotype. Conversely, colonies exposed to pesticide-treated pollen had a reduced capacity for viable queen production, and among surviving queens from these colonies we observed lower sperm viability. We found no difference in queen mating number across treatments. Moreover, we measured lower brood viability in colonies later established by queens reared in treated-pollen colonies. Interestingly, royal jelly from colonies exposed to treated pollen contained negligible pesticide residues, suggesting the indirect social consequences of colony-level pesticide exposure on queen quality. These findings highlight how conditions during developmental can impact queens long into adulthood, and that colony-level pesticide exposure may do so indirectly.

Metabolite Support of Long-Term Storage of Sperm in the Spermatheca of Honeybee (Apis mellifera) Queens

The polyandrous mating system of honeybees (Apis mellifera L.) has garnered widespread attention. Long-lived honeybee queens only mate early in maturation, and the sperm obtained from the aerial mating is stored in the spermatheca. The maintenance of sperm viability in the spermatheca is an intriguing and complex process. However, the key physiological and biochemical adaptations underlying the long-term storage of sperm remain unclear. Analysis of the metabolite profile could help better understand the biology of the spermatheca and offer insights into the breeding and conservation of honeybees and even pest control strategies. Here, the changes in metabolites in the spermatheca were quantified between virgin queens and new-laying queens (with stored sperm) via liquid chromatography-mass spectrometry. Compared with virgin queens, changes occurred in lipids and lipid-like molecules, including fatty acyls and glycerophospholipids (GPL), prenol lipids, and sterol lipids, during storage of sperm in new-laying honeybee queens. Furthermore, the metabolic pathways that were enriched with the differentially expressed metabolites were identified and included GPL metabolism, biosynthesis of amino acids, and the mTOR signaling pathway. The likely roles of the pathways in the maintenance and protection of sperm are discussed. The study identifies key metabolites and pathways in the complex interplay of substances that contribute to the long-term storage of sperm and ultimately reproductive success of honeybee queens.

Modulation by neonicotinoids of honeybee α1/chicken β2 hybrid nicotinic acetylcholine receptors expressed in Xenopus laevis oocytes

Neonicotinoids targeting insect nicotinic acetylcholine (ACh) receptors (insect nAChRs) are used for crop protection, but there is a concern about adverse effects on pollinators such as honeybees (Apis mellifera). Thus, we investigated the agonist actions of neonicotinoids (imidacloprid, thiacloprid and clothianidin) on A. mellifera α1 (Amα1)/chicken β2 hybrid nAChRs in Xenopus laevis oocytes according to the subunit stoichiometry of (Amα1)₃(β2)₂ and (Amα1)₂(β2)₃ using voltage-clamp electrophysiology. ACh activated (Amα1)₃(β2)₂ and (Amα1)₂(β2)₃ nAChRs with similar current amplitude. We investigated the agonist activity of imidacloprid, thiacloprid and clothianidin for the two hybrid nAChRs and found that: 1) imidacloprid showed higher affinity than clothianidin, whereas clothianidin showed higher efficacy than imidacloprid for the nAChRs; 2) Thiacloprid showed the highest agonist affinity and the lowest efficacy for the nAChRs. The Amα1/β2 subunit ratio influenced the efficacy of imidacloprid and thiacloprid, but hardly affected that of clothianidin. Hydrogen bond formation by the NH group in clothianidin with the main chain carbonyl of the loop B may account, at least in part, for the unique agonist actions of clothianidin on the hybrid nAChRs tested.

The weakest link: Haploid honey bees are more susceptible to neonicotinoid insecticides

Neonicotinoid insecticides are currently of major concern for the health of wild and managed insects that provide key ecosystem services like pollination. Even though sublethal effects of neonicotinoids are well known, there is surprisingly little information on how they possibly impact developmental stability, and to what extent genetics are involved. This holds especially true for haploid individuals because they are hemizygous at detoxification loci and may be more susceptible. Here we take advantage of haplodiploidy in Western honey bees, Apis mellifera, to show for the first time that neonicotinoids affect developmental stability in diploid females (workers), and that haploid males (drones) are even more susceptible. Phenotypic fore wing venation abnormalities and fluctuating wing asymmetry, as measures of developmental instability, were significantly increased under field-realistic neonicotinoid-exposure of colonies. The higher susceptibility of haploid drones suggests that heterozygosity can play a key role in the ability to buffer the sublethal effects of neonicotinoids. Aiming to improve conservation efforts, our findings highlight the urgent need to better understand the role that genetics plays at enabling non-target organisms to cope with insecticide exposure.

Pesticide contamination drives adaptive genetic variation in the endemic mayfly Andesiops torrens within a semi-arid agricultural watershed of Chile

Agrichemical contamination can provoke evolutionary responses in freshwater populations. It is a particularly relevant issue in semi-arid regions due to the sensitivity of endemic species to pollutants and to interactions with temperature stress. This paper investigates the presence of pesticides in rivers within a semi-arid agricultural watershed of Chile, testing for their effects on population genetic characteristics of the endemic mayfly Andesiops torrens (Insecta, Ephemeroptera). Pesticides were detected in sediment samples in ten out of the 30 sites analyzed throughout the upper part of the Limarí watershed. To study the evolutionary impact of such contamination on A. torrens, we used a genome-wide approach and analyzed 2056 single nucleotide polymorphisms (SNPs) loci in 551 individuals from all sites. Genetic differentiation was weak between populations, suggesting high gene flow across the study area. While we did not find evidence of pesticide effects on genetic diversity nor on population differentiation, the allele frequency of three outlier SNP loci correlated significantly with pesticide occurrence. Interrogation of genomic resources indicates that two of these SNPs are located within functional genes that encode for the low-density lipoprotein receptor-related protein 2 and Dumpy, both potentially involved in insect cuticle resistance processes. Such genomic signatures of local adaptation are indicative of past adverse effects of pesticide exposure on the locally adapted populations. Our results reveal that A. torrens is sensitive to pesticide exposure, but that a high gene flow may confer resilience to contamination. This research supports the contention that A. torrens is an ideal model organism to study evolutionary responses induced by pesticides on non-target, endemic species.

Long-term dynamics of honey bee colonies following exposure to chemical stress

Pesticide residues have been linked to reduced bee health and increased honey bee colony failure. Most research to date has investigated the role of pesticides on individual honey bees, and it is still unclear how trace levels of pesticides change colony viability and productivity over seasonal time scales. To address this question we exposed standard bee colonies to chemical stressors known to have negative effects on individual bees, and measured the productivity of bee colonies across a whole year in two environments: near Tucson Arizona and Sydney Australia. We exposed hives to a trace amount of the neonicotinoid imidacloprid and to the acaricide thymol, and measured capped brood, bee and honey production, as well as the temperature and foraging force of the colonies. The effect of imidacloprid on colony dynamics differed between the two environments. In Tucson we recorded a positive effect of imidacloprid treatment on bee and brood numbers. Thymol was associated with short-term negative effects on bee numbers at both locations, and may have affected colony survival at one location. The overall benefits of thymol for the colonies were unclear. We conclude that long-term and colony-level measures of the effects of agrochemicals are needed to properly understand risks to bees.

Effect of Sub-lethal Doses of Imidacloprid on Learning and Memory Formation of Indigenous Arabian Bee (Apis mellifera jemenitica Ruttner) Adult Foragers

The indigenous bee race Apis mellifera jemenitica Ruttner of Saudi Arabia can learn and retain memories established by the classical conditioning of proboscis extension response (PER). The insecticide imidacloprid has shown a drastic effect on the olfactory behavior of A. m. jemenitica in the harsh arid climatic conditions of central Saudi Arabia. The oral feeding of single imidacloprid sub-lethal doses (1.0 ng, 0.5 ng, or 0.1 ng) under laboratory conditions significantly impaired associative learning during the 2nd and 3rd conditioning trials compared to control bees (0 ng). The memory tests also revealed significant impairment in memory formation at 1 h, 2 h, and 24 h after conditioning compared to control bees. Even the lowest dose (0.1 ng/bee) can significantly impair the bees' ability to learn and memorize. This impairment effect was dose dependent and increased with increasing doses. The higher dose (1.0 ng) completely impaired the learning but still showed a little memory and reflected the potential recovery of bees from insecticide-induced impairment with the passage of time. To our knowledge, this is the first study in A. m. jemenitica that demonstrated the drastic effect of neonicotinoids on associative learning in indigenous bees. This study further expresses the possible severity of insecticidal exposure to bees in actual field conditions and its effect on the neural functions used in important behavior involved in the foraging of bees.

Quantum Yields and N2O Formation from Photolysis of Solid Films of Neonicotinoids

Neonicotinoids (NN), first introduced in 1991, are found on environmental surfaces where they undergo photolytic degradation. Photolysis studies of thin films of NN were performed using two approaches: (1) transmission FTIR, in which solid films of NN and the gas-phase products were analyzed simultaneously, and (2) attenuated-total-reflectance FTIR combined with transmission FTIR, in which solid films of NN and the gas-phase products were probed in the same experiment but not at the same time. Photolysis quantum yields using broadband irradiation centered at 313 nm were (2.2 ± 0.9) × 10^-3 for clothianidin (CLD), (3.9 ± 0.3) × 10^-3 for thiamethoxam (TMX), and (3.3 ± 0.5) × 10^-3 for dinotefuran (DNF), with all errors being ±1 s. At 254 nm, which was used to gain insight into the wavelength dependence, quantum yields were in the range of (0.8-20) × 10^-3 for all NNs, including acetamiprid (ACM) and thiacloprid (TCD). Nitrous oxide (N₂O), a potent greenhouse gas, was the only gas-phase product detected for the photolysis of nitroguanidines, with yields of ΔN₂O/ΔNN > 0.5 in air at both 313 and 254 nm. The atmospheric lifetimes with respect to photolysis for CLD, TMX, and DNF, which absorb light in the actinic region, are estimated to be 15, 10, and 11 h, respectively, at a solar zenith angle of 35° and 12, 8, and 10 h at a solar zenith angle of 15°.

Genetic Diversity in the Progeny of Commercial Australian Queen Honey Bees (Hymenoptera: Apidae) Produced in Autumn and Early Spring

Honey bee [Apis mellifera L. (Hymenoptera: Apidae)] queens are polyandrous, mating with an average 12 males (drones). Polyandry has been shown to confer benefits to queens and the colonies they head, including avoidance of inviable brood that can arise via sex locus homozygosity, increased resilience to pests and pathogens, and increased survival and productivity, leading to improved colony-level fitness. Queens with an effective mating frequency (ke) greater than 7 are considered adequately mated, whereas queens that fall below this threshold head colonies that have increased likelihood of failure and may be less productive for beekeepers. We determined ke in queens produced in early Spring and Autumn by five Australian commercial queen producers to determine whether the queens they produced were suitably mated. Drone populations are low at these times of year, and therefore, there is an increased risk that queens would fall below the ke > 7 threshold. We found that 33.8% of Autumn-produced queens did not meet the threshold, whereas 93.8% of Spring queens were adequately mated. The number of colonies contributing drones to the mating pool was similarly high in both seasons, suggesting that although many colonies have drones, their numbers may be decreased in Autumn and management strategies may be required to boost drone numbers at this time. Finally, queens had similar levels of homozygosity to workers, and inbreeding coefficients were very low, suggesting that inbreeding is not a problem.

Harnessing model organisms to study insecticide resistance

The vinegar fly, Drosophila melanogaster, has made an enormous contribution to our understanding of insecticide targets, metabolism and transport. This contribution has been enabled by the unmatched capacity to manipulate genes in D. melanogaster and the fact that lessons learn in this system have been applicable to pests, because of the evolutionary conservation of key genes, particularly those encoding targets. With the advent of the CRISPR-Cas9 gene editing technology, genes can now be manipulated in pest species, but this review points to advantages that are likely to keep D. melanogaster at the forefront of insecticide research.