Exposure to sublethal doses of fipronil and thiacloprid highly increases mortality of honeybees previously infected by Nosema ceranae

Current knowledge of detoxification mechanisms of xenobiotic in honey bees

The western honey bee Apis mellifera is the most important managed pollinator species in the world. Multiple factors have been implicated as potential causes or factors contributing to colony collapse disorder, including honey bee pathogens and nutritional deficiencies as well as exposure to pesticides. Honey bees' genome is characterized by a paucity of genes associated with detoxification, which makes them vulnerable to specific pesticides, especially to combinations of pesticides in real field environments. Many studies have investigated the mechanisms involved in detoxification of xenobiotics/pesticides in honey bees, from primal enzyme assays or toxicity bioassays to characterization of transcript gene expression and protein expression in response to xenobiotics/insecticides by using a global transcriptomic or proteomic approach, and even to functional characterizations. The global transcriptomic and proteomic approach allowed us to learn that detoxification mechanisms in honey bees involve multiple genes and pathways along with changes in energy metabolism and cellular stress response. P450 genes, is highly implicated in the direct detoxification of xenobiotics/insecticides in honey bees and their expression can be regulated by honey/pollen constitutes, resulting in the tolerance of honey bees to other xenobiotics or insecticides. P450s is also a key detoxification enzyme that mediate synergism interaction between acaricides/insecticides and fungicides through inhibition P450 activity by fungicides or competition for detoxification enzymes between acaricides. With the wide use of insecticides in agriculture, understanding the detoxification mechanism of insecticides in honey bees and how honeybees fight with the xenobiotis or insecticides to survive in the changing environment will finally benefit honeybees' management.

Assessment of the mutagenic, recombinogenic and carcinogenic potential of fipronil insecticide in somatic cells of Drosophila melanogaster

Fipronil (FP) is an insecticide that belongs to the phenylpyrazole chemical family and is used to control pests by blocking GABA receptor at the entrance channel of the chlorine neurons. The aim of this study was to evaluate the mutagenic, recombinogenic and carcinogenic potential of FP. The mutagenic and recombinogenic effects were evaluated using the somatic mutation and recombination test (SMART) on wing cells of Drosophila melanogaster. Third instar larvae from standard (ST) and high bioactivation (HB) crosses were treated with different concentrations of FP (0.3, 0.7, 1.5 or 3.0 × 10^-5 mM). The results showed mutagenic effects at all concentrations tested in the HB cross; and all concentrations tested in the ST cross, except at concentration of 0.7 × 10^-5 mM. The carcinogenic effect of FP was assayed through the test for detection of epithelial tumor (warts) in D. melanogaster. Third instar larvae from wts/TM3 virgin females mated to mwh/mwh males were treated with different concentrations of FP (0.3, 0.7, 1.5 or 3.0 × 10^-5 mM). All these concentrations induced a statistically significant increase in tumor frequency. In conclusion, FP proved to be mutagenic, recombinogenic and carcinogenic in somatic cells of D. melanogaster.

Comparison of fipronil sources in North Carolina surface water and identification of a novel fipronil transformation product in recycled wastewater

Fipronil is a phenylpyrazole insecticide that is widely used in residential and agricultural settings to control ants, roaches, termites, and other pests. Fipronil and its transformation products have been found in a variety of environmental matrices, but the source[s] which makes the greatest contribution to fipronil in surface water has yet to be determined. A sampling effort designed to prioritize known fipronil inputs (golf courses, residential areas, biosolids application sites and wastewater facilities) was conducted in North Carolina to learn more about the origins of fipronil in surface water. High resolution mass spectrometry (HRMS) analysis indicated that fipronil and its known derivatives were routinely present in all samples, but concentrations were substantially elevated near wastewater treatment plant outfalls (range 10-500ng/L combined), suggesting that they predominate as environmental sources. Corresponding recycled wastewater samples, which were treated with NaOCl for disinfection, showed disappearance of fipronil and all known degradates. HRMS and nuclear magnetic resonance (NMR) analysis techniques were used to determine that all fipronil-related compounds are oxidized to a previously unidentified fipronil sulfone chloramine species in recycled wastewater. The implications of the presence of a new fipronil-related compound in recycled wastewater need to be considered.

Large-scale monitoring of effects of clothianidin-dressed oilseed rape seeds on pollinating insects in Northern Germany: effects on honey bees (Apis mellifera)

Possible effects of clothianidin seed-treated oilseed rape on honey bee colonies were investigated in a large-scale monitoring project in Northern Germany, where oilseed rape usually comprises 25-33 % of the arable land. For both reference and test sites, six study locations were selected and eight honey bee hives were placed at each location. At each site, three locations were directly adjacent to oilseed rape fields and three locations were situated 400 m away from the nearest oilseed rape field. Thus, 96 hives were exposed to fully flowering oilseed rape crops. Colony sizes and weights, the amount of honey harvested, and infection with parasites and diseases were monitored between April and September 2014. The percentage of oilseed rape pollen was determined in pollen and honey samples. After oilseed rape flowering, the hives were transferred to an extensive isolated area for post-exposure monitoring. Total numbers of adult bees and brood cells showed seasonal fluctuations, and there were no significant differences between the sites. The honey, which was extracted at the end of the exposure phase, contained 62.0-83.5 % oilseed rape pollen. Varroa destructor infestation was low during most of the course of the study but increased at the end of the study due to flumethrin resistance in the mite populations. In summary, honey bee colonies foraging in clothianidin seed-treated oilseed rape did not show any detrimental symptoms as compared to colonies foraging in clothianidin-free oilseed rape. Development of colony strength, brood success as well as honey yield and pathogen infection were not significantly affected by clothianidin seed-treatment during this study.

Age structure is critical to the population dynamics and survival of honeybee colonies

Age structure is an important feature of the division of labour within honeybee colonies, but its effects on colony dynamics have rarely been explored. We present a model of a honeybee colony that incorporates this key feature, and use this model to explore the effects of both winter and disease on the fate of the colony. The model offers a novel explanation for the frequently observed phenomenon of 'spring dwindle', which emerges as a natural consequence of the age-structured dynamics. Furthermore, the results indicate that a model taking age structure into account markedly affects the predicted timing and severity of disease within a bee colony. The timing of the onset of disease with respect to the changing seasons may also have a substantial impact on the fate of a honeybee colony. Finally, simulations predict that an infection may persist in a honeybee colony over several years, with effects that compound over time. Thus, the ultimate collapse of the colony may be the result of events several years past.

Silencing the Honey Bee (Apis mellifera) Naked Cuticle Gene (nkd) Improves Host Immune Function and Reduces Nosema ceranae Infections

Nosema ceranae is a new and emerging microsporidian parasite of European honey bees, Apis mellifera, that has been implicated in colony losses worldwide. RNA interference (RNAi), a posttranscriptional gene silencing mechanism, has emerged as a potent and specific strategy for controlling infections of parasites and pathogens in honey bees. While previous studies have focused on the silencing of parasite/pathogen virulence factors, we explore here the possibility of silencing a host factor as a mechanism for reducing parasite load. Specifically, we used an RNAi strategy to reduce the expression of a honey bee gene, naked cuticle (nkd), which is a negative regulator of host immune function. Our studies found that nkd mRNA levels in adult bees were upregulated by N. ceranae infection (and thus, the parasite may use this mechanism to suppress host immune function) and that ingestion of double-stranded RNA (dsRNA) specific to nkd efficiently silenced its expression. Furthermore, we found that RNAi-mediated knockdown of nkd transcripts in Nosema-infected bees resulted in upregulation of the expression of several immune genes (Abaecin, Apidaecin, Defensin-1, and PGRP-S2), reduction of Nosema spore loads, and extension of honey bee life span. The results of our studies clearly indicate that silencing the host nkd gene can activate honey bee immune responses, suppress the reproduction of N. ceranae, and improve the overall health of honey bees. This study represents a novel host-derived therapeutic for honey bee disease treatment that merits further exploration.

IMPORTANCE

Given the critical role of honey bees in the pollination of agricultural crops, it is urgent to develop strategies to prevent the colony decline induced by the infection of parasites/pathogens. Targeting parasites and pathogens directly by RNAi has been proven to be useful for controlling infections in honey bees, but little is known about the disease impacts of RNAi silencing of host factors. Here, we demonstrate that knocking down the honey bee immune repressor-encoding nkd gene can suppress the reproduction of N. ceranae and improve the overall health of honey bees, which highlights the potential role of host-derived and RNAi-based therapeutics in controlling the infections in honey bees. The information obtained from this study will have positive implications for honey bee disease management practices.

The Differential Effect of Low-Dose Mixtures of Four Pesticides on the Pea Aphid Acyrthosiphon pisum

The modes of action of most insecticides are known, but little information exists regarding the toxicological interactions involving insecticide mixtures at low doses. The effects of mixtures of four insecticides were investigated using LC₁₀ values (concentration leading to 10% mortality), acetamiprid (ACE, 0.235 µg/mL), chlorpyriphos (CHL, 107.0 µg/mL), deltamethrin (DEL, 5.831 µg/mL), and fipronil (FIP, 3.775 µg/mL) on the larvae of the pea aphid, Acyrthosiphon pisum. After 24 h exposure, 6 of the 11 tested combinations, DEL/FIP, ACE/DEL, CHL/FIP, ACE/DEL/FIP, ACE/CHL/FIP, and ACE/DEL/CHL/FIP, were toxic through an additive effect. Four combinations, ACE/FIP, DEL/CHL, ACE/CHL, and ACE/DEL/CHL had a synergistic effect, whereas only one DEL/CHL/FIP showed an antagonistic effect. The toxic effect of these mixtures was confirmed after 48 h of exposure, revealing an enhanced toxicity of CHL, DEL, and FIP in combination with ACE. We suggest that an insect pest management strategy should be evaluated in the future using different combinations of insecticides.

Beneficial microorganisms for honey bees: problems and progresses

Nowadays, honey bees are stressed by a number of biotic and abiotic factors which may compromise to some extent the pollination service and the hive productivity. The EU ban of antibiotics as therapeutic agents against bee pathogens has stimulated the search for natural alternatives. The increasing knowledge on the composition and functions of the bee gut microbiota and the link between a balanced gut microbiota and health status have encouraged the research on the use of gut microorganisms to improve bee health. Somehow, we are assisting to the transfer of the "probiotic concept" into the bee science. In this review, we examine the role of the honey bee gut microbiota in bee health and critically describe the available applications of beneficial microorganisms as pest control agents and health support. Most of the strains, mainly belonging to the genera Lactobacillus, Bifidobacterium and Bacillus, are isolated from honey bee crop or gut, but some applications involve environmental strains or formulation for animal and human consumption. Overall, the obtained results show the favourable effect of applied microbial strains on bee health and productivity, in particular if strains of bee origin are used. However, it is actually not yet possible to conclude whether this strategy will ever work. In particular, many aspects regarding the overall setup of the experiments, the dose, the timing and the duration of the treatment need to be optimized, also considering the microbiological safety of the hive products (i.e. pollen and honey). In addition, a deep investigation about the effect on host immunity and physiology is envisaged. Lastly, the final users of the formulations, i.e. beekeepers, should be taken into account for the achievement of high-quality, cost-effective and easy-to-use products.

Sub-lethal effects of dietary neonicotinoid insecticide exposure on honey bee queen fecundity and colony development

Many factors can negatively affect honey bee (Apis mellifera L.) health including the pervasive use of systemic neonicotinoid insecticides. Through direct consumption of contaminated nectar and pollen from treated plants, neonicotinoids can affect foraging, learning, and memory in worker bees. Less well studied are the potential effects of neonicotinoids on queen bees, which may be exposed indirectly through trophallaxis, or food-sharing. To assess effects on queen productivity, small colonies of different sizes (1500, 3000, and 7000 bees) were fed imidacloprid (0, 10, 20, 50, and 100 ppb) in syrup for three weeks. We found adverse effects of imidacloprid on queens (egg-laying and locomotor activity), worker bees (foraging and hygienic activities), and colony development (brood production and pollen stores) in all treated colonies. Some effects were less evident as colony size increased, suggesting that larger colony populations may act as a buffer to pesticide exposure. This study is the first to show adverse effects of imidacloprid on queen bee fecundity and behavior and improves our understanding of how neonicotinoids may impair short-term colony functioning. These data indicate that risk-mitigation efforts should focus on reducing neonicotinoid exposure in the early spring when colonies are smallest and queens are most vulnerable to exposure.

Honey Bee Gut Microbiome Is Altered by In-Hive Pesticide Exposures

Honey bees (Apis mellifera) are the primary pollinators of major horticultural crops. Over the last few decades, a substantial decline in honey bees and their colonies have been reported. While a plethora of factors could contribute to the putative decline, pathogens, and pesticides are common concerns that draw attention. In addition to potential direct effects on honey bees, indirect pesticide effects could include alteration of essential gut microbial communities and symbionts that are important to honey bee health (e.g., immune system). The primary objective of this study was to determine the microbiome associated with honey bees exposed to commonly used in-hive pesticides: coumaphos, tau-fluvalinate, and chlorothalonil. Treatments were replicated at three independent locations near Blacksburg Virginia, and included a no-pesticide amended control at each location. The microbiome was characterized through pyrosequencing of V2-V3 regions of the bacterial 16S rRNA gene and fungal ITS region. Pesticide exposure significantly affected the structure of bacterial but not fungal communities. The bee bacteriome, similar to other studies, was dominated by sequences derived from Bacilli, Actinobacteria, α-, β-, γ-proteobacteria. The fungal community sequences were dominated by Ascomycetes and Basidiomycetes. The Multi-response permutation procedures (MRPP) and subsequent Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis indicated that chlorothalonil caused significant change to the structure and functional potential of the honey bee gut bacterial community relative to control. Putative genes for oxidative phosphorylation, for example, increased while sugar metabolism and peptidase potential declined in the microbiome of chlorothalonil exposed bees. The results of this field-based study suggest the potential for pesticide induced changes to the honey bee gut microbiome that warrant further investigation.

Phthalate pollution in an Amazonian rainforest

Phthalates are ubiquitous contaminants and endocrine-disrupting chemicals that can become trapped in the cuticles of insects, including ants which were recognized as good bioindicators for such pollution. Because phthalates have been noted in developed countries and because they also have been found in the Arctic, a region isolated from direct anthropogenic influence, we hypothesized that they are widespread. So, we looked for their presence on the cuticle of ants gathered from isolated areas of the Amazonian rainforest and along an anthropogenic gradient of pollution (rainforest vs. road sides vs. cities in French Guiana). Phthalate pollution (mainly di(2-ethylhexyl) phthalate (DEHP)) was higher on ants gathered in cities and along road sides than on those collected in the pristine rainforest, indicating that it follows a human-mediated gradient of disturbance related to the use of plastics and many other products that contain phthalates in urban zones. Their presence varied with the ant species; the cuticle of Solenopsis saevissima traps higher amount of phthalates than that of compared species. However, the presence of phthalates in isolated areas of pristine rainforests suggests that they are associated both with atmospheric particles and in gaseous form and are transported over long distances by wind, resulting in a worldwide diffusion. These findings suggest that there is no such thing as a "pristine" zone.

Honey Bees' Behavior Is Impaired by Chronic Exposure to the Neonicotinoid Thiacloprid in the Field

The decline of pollinators worldwide is of growing concern and has been related to the use of plant-protecting chemicals. Most studies have focused on three neonicotinoid insecticides (clothianidin, imidacloprid, and thiamethoxam) currently subject to a moratorium in the EU. Here, we focus on thiacloprid, a widely used cyano-substituted neonicotinoid thought to be less toxic to honey bees and of which use has increased in the last years. Honey bees (Apis mellifera carnica) were exposed chronically to thiacloprid in the field for several weeks at a sublethal concentration. Foraging behavior, homing success, navigation performance, and social communication were impaired, and thiacloprid residue levels increased both in the foragers and the nest mates over time. The effects observed in the field were not due to a repellent taste of the substance. For the first time, we present the necessary data for the risk evaluation of thiacloprid taken up chronically by honey bees in field conditions.

Honeybees Produce Millimolar Concentrations of Non-Neuronal Acetylcholine for Breeding: Possible Adverse Effects of Neonicotinoids

The worldwide use of neonicotinoid pesticides has caused concern on account of their involvement in the decline of bee populations, which are key pollinators in most ecosystems. Here we describe a role of non-neuronal acetylcholine (ACh) for breeding of Apis mellifera carnica and a so far unknown effect of neonicotinoids on non-target insects. Royal jelly or larval food are produced by the hypopharyngeal gland of nursing bees and contain unusually high ACh concentrations (4–8 mM). ACh is extremely well conserved in royal jelly or brood food because of the acidic pH of 4.0. This condition protects ACh from degradation thus ensuring delivery of intact ACh to larvae. Raising the pH to ≥5.5 and applying cholinesterase reduced the content of ACh substantially (by 75–90%) in larval food. When this manipulated brood was tested in artificial larval breeding experiments, the survival rate was higher with food supplemented by 100% with ACh (6 mM) than with food not supplemented with ACh. ACh release from the hypopharyngeal gland and its content in brood food declined by 80%, when honeybee colonies were exposed for 4 weeks to high concentrations of the neonicotinoids clothianidin (100 parts per billion [ppb]) or thiacloprid (8,800 ppb). Under these conditions the secretory cells of the gland were markedly damaged and brood development was severely compromised. Even field-relevant low concentrations of thiacloprid (200 ppb) or clothianidin (1 and 10 ppb) reduced ACh level in the brood food and showed initial adverse effects on brood development. Our findings indicate a hitherto unknown target of neonicotinoids to induce adverse effects on non-neuronal ACh which should be considered when re-assessing the environmental risks of these compounds. To our knowledge this is a new biological mechanism, and we suggest that, in addition to their well documented neurotoxic effects, neonicotinoids may contribute to honeybee colony losses consecutive to a reduction of the ACh content in the brood food.

Sperm viability and gene expression in honey bee queens (Apis mellifera) following exposure to the neonicotinoid insecticide imidacloprid and the organophosphate acaricide coumaphos

Honey bee population declines are of global concern. Numerous factors appear to cause these declines including parasites, pathogens, malnutrition and pesticides. Residues of the organophosphate acaricide coumaphos and the neonicotinoid insecticide imidacloprid, widely used to combat Varroa mites and for crop protection in agriculture, respectively, have been detected in wax, pollen and comb samples. Here, we assess the effects of these compounds at different doses on the viability of sperm stored in the honey bee queens' spermatheca. Our results demonstrate that sub-lethal doses of imidacloprid (0.02ppm) decreased sperm viability by 50%, 7days after treatment. Sperm viability was a downward trend (about 33%) in queens treated with high doses of coumaphos (100ppm), but there was not significant difference. The expression of genes that are involved in development, immune responses and detoxification in honey bee queens and workers exposed to chemicals was measured by qPCR analysis. The data showed that expression levels of specific genes were triggered 1day after treatment. The expression levels of P450 subfamily genes, CYP306A1, CYP4G11 and CYP6AS14 were decreased in honey bee queens treated with low doses of coumaphos (5ppm) and imidacloprid (0.02ppm). Moreover, these two compounds suppressed the expression of genes related to antioxidation, immunity and development in queens at day 1. Up-regulation of antioxidants by these compounds in worker bees was observed at day 1. Coumaphos also caused a repression of CYP306A1 and CYP4G11 in workers. Antioxidants appear to prevent chemical damage to honey bees. We also found that DWV replication increased in workers treated with imidacloprid. This research clearly demonstrates that chemical exposure can affect sperm viability in queen honey bees.

Persistence of fipronil residues in Eucalyptus seedlings and its concentration in the insecticide solution after treatment in the nursery

Eucalyptus seedlings are normally protected from underground termites (Isoptera: Termitidae) by immersing them in insecticide solutions. Fipronil (phenylpyrazole) is the most frequently used product to protect seedlings in the field for up to 6 months after application. This is performed just prior to planting. However, the persistence of this product in seedlings that are treated and subjected to irrigation several days prior to planting has not yet been evaluated. This study aims to quantify the fipronil concentration in the substratum and roots of the seedlings treated and subjected to irrigation for up to 56 days prior to planting and to quantify this insecticide concentration in the solutions, without continuous stirring, for 120 min. The quantitative determination of fipronil in the seedlings and in the insecticide solution was done by high-performance liquid chromatography (HPLC) with an ultraviolet (UV) detector. It was found that irrigation up to 56 days, performed in the nurseries, did not decrease the fipronil concentration in the seedlings. The absence of stirring reduced the fipronil concentration in the insecticide solution, necessitating a homogenization system to maintain the recommended concentration of this product, to effectively treat the eucalyptus seedlings. The seedling treatment with fipronil can be conducted strictly in the nursery, reducing cost and environmental risks.

Chronic toxicity and physiological changes induced in the honey bee by the exposure to fipronil and Bacillus thuringiensis spores alone or combined

In the agricultural environment, honey bees may be exposed to combinations of pesticides. Until now, the effects of these combinations on honey bee health have been poorly investigated. In this study, we assessed the impacts of biological and chemical insecticides, combining low dietary concentrations of Bacillus thuringiensis (Bt) spores (100 and 1000µg/L) with the chemical insecticide fipronil (1µg/L). In order to assess the possible effects of Cry toxins, the Bt kurstaki strain (Btk) was compared with a Bt strain devoid of toxin-encoding plasmids (Bt Cry(-)). The oral exposure to fipronil and Bt spores from both strains for 10 days did not elicit significant effects on the feeding behavior and survival after 25 days. Local and systemic physiological effects were investigated by measuring the activities of enzymes involved in the intermediary and detoxication metabolisms at two sampling dates (day 10 and day 20). Attention was focused on head and midgut glutathione-S-transferase (GST), midgut alkaline phosphatase (ALP), abdomen glyceraldehyde-3-phosphate dehydrogenase (GAPD) and glucose-6-phosphate dehydrogenase (G6PD). We found that Bt Cry(-) and Btk spores induced physiological modifications by differentially modulating enzyme activities. Fipronil influenced the enzyme activities differently at days 10 and 20 and, when combined with Bt spores, elicited modulations of some spore-induced physiological responses. These results show that an apparent absence of toxicity may hide physiological disruptions that could be potentially damaging for the bees, especially in the case of combined exposures to other environmental stressors.

Is there a link between pollutant exposure and emerging infectious disease?

A scoping literature review found evidence supporting the hypothesis that a population's pollution status could help refine classification of emerging infectious disease (EID) hotspots. Systematic literature reviews and studies designed to specifically test the predictive value of pollutant status on EID risk are recommended.

Are bee diseases linked to pesticides? - A brief review

The negative impacts of pesticides, in particular insecticides, on bees and other pollinators have never been disputed. Insecticides can directly kill these vital insects, whereas herbicides reduce the diversity of their food resources, thus indirectly affecting their survival and reproduction. At sub-lethal level (<LD50), neurotoxic insecticide molecules are known to influence the cognitive abilities of bees, impairing their performance and ultimately impacting on the viability of the colonies. In addition, widespread systemic insecticides appear to have introduced indirect side effects on both honey bees and wild bumblebees, by deeply affecting their health. Immune suppression of the natural defences by neonicotinoid and phenyl-pyrazole (fipronil) insecticides opens the way to parasite infections and viral diseases, fostering their spread among individuals and among bee colonies at higher rates than under conditions of no exposure to such insecticides. This causal link between diseases and/or parasites in bees and neonicotinoids and other pesticides has eluded researchers for years because both factors are concurrent: while the former are the immediate cause of colony collapses and bee declines, the latter are a key factor contributing to the increasing negative impact of parasitic infections observed in bees in recent decades.

Divergent forms of endoplasmic reticulum stress trigger a robust unfolded protein response in honey bees

Honey bee colonies in the United States have suffered from an increased rate of die-off in recent years, stemming from a complex set of interacting stresses that remain poorly described. While we have some understanding of the physiological stress responses in the honey bee, our molecular understanding of honey bee cellular stress responses is incomplete. Thus, we sought to identify and began functional characterization of the components of the UPR in honey bees. The IRE1-dependent splicing of the mRNA for the transcription factor Xbp1, leading to translation of an isoform with more transactivation potential, represents the most conserved of the UPR pathways. Honey bees and other Apoidea possess unique features in the Xbp1 mRNA splice site, which we reasoned could have functional consequences for the IRE1 pathway. However, we find robust induction of target genes upon UPR stimulation. In addition, the IRE1 pathway activation, as assessed by splicing of Xbp1 mRNA upon UPR, is conserved. By providing foundational knowledge about the UPR in the honey bee and the relative sensitivity of this species to divergent stresses, this work stands to improve our understanding of the mechanistic underpinnings of honey bee health and disease.

Effects of Nosema ceranae and thiametoxam in Apis mellifera: A comparative study in Africanized and Carniolan honey bees

Multiple stressors, such as chemicals and pathogens, are likely to be detrimental for the health and lifespan of Apis mellifera, a bee species frequently exposed to both factors in the field and inside hives. The main objective of the present study was to evaluate comparatively the health of Carniolan and Africanized honey bees (AHB) co-exposed to thiamethoxam and Nosema ceranae (N. ceranae) spores. Newly-emerged worker honey bees were exposed solely with different sublethal doses of thiamethoxam (2% and 0.2% of LD50 for AHB), which could be consumed by bees under field conditions. Toxicity tests for the Carniolan bees were performed, and the LD50 of thiamethoxam for Carniolan honey bees was 7.86 ng bee(-1). Immunohistological analyses were also performed to detect cell death in the midgut of thiamethoxam and/or N. ceranae treated bees. Thiamethoxam exposure had no negative impact on Nosema development in experimental conditions, but it clearly inhibited cell death in the midgut of thiamethoxam and Nosema-exposed bees, as demonstrated by immunohistochemical data. Indeed, thiamethoxam exposure only had a minor synergistic toxic effect on midgut tissue when applied as a low dose simultaneously with N. ceranae to AHB and Carniolan honey bees, in comparison with the effect caused by both stressors separately. Our data provides insights into the effects of the neonicotenoid thiamethoxam on the AHB and Carniolan honey bee life span, as well as the effects of simultaneous application of thiamethoxam and N. ceranae spores to honey bees.

Parasite infection accelerates age polyethism in young honey bees

Honey bees (Apis mellifera) are important pollinators and their health is threatened worldwide by persistent exposure to a wide range of factors including pesticides, poor nutrition, and pathogens. Nosema ceranae is a ubiquitous microsporidian associated with high colony mortality. We used lab micro-colonies of honey bees and video analyses to track the effects of N. ceranae infection and exposure on a range of individual and social behaviours in young adult bees. We provide detailed data showing that N. ceranae infection significantly accelerated the age polyethism of young bees, causing them to exhibit behaviours typical of older bees. Bees with high N. ceranae spore counts had significantly increased walking rates and decreased attraction to queen mandibular pheromone. Infected bees also exhibited higher rates of trophallaxis (food exchange), potentially reflecting parasite manipulation to increase colony infection. However, reduction in queen contacts could help bees limit the spread of infection. Such accelerated age polyethism may provide a form of behavioural immunity, particularly if it is elicited by a wide variety of pathogens.

Active Sampling Device for Determining Pollutants in Surface and Pore Water - the In Situ Sampler for Biphasic Water Monitoring

We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040–0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction.

Mass Balance of Fipronil and Total Toxicity of Fipronil-Related Compounds in Process Streams during Conventional Wastewater and Wetland Treatment

Attenuation of the pesticide fipronil and its major degradates was determined during conventional wastewater treatment and wetland treatment. Analysis of flow-weighted composite samples by liquid and gas chromatography-tandem mass spectrometry showed fipronil occurrence at 12-31 ng/L in raw sewage, primary effluent, secondary effluent, chlorinated effluent, and wetland effluent. Mean daily loads of total fipronil related compounds in raw sewage and in plant effluent after chlorination were statistically indistinguishable (p = 0.29; n = 10), whereas fipronil itself was partially removed (25 ± 3%; p = 0.00025; n = 10); the associated loss in toxicity was balanced by the formation of toxic fipronil degradates, showing conventional treatment to be unfit for reducing overall toxicity. In contrast to these findings at the municipal wastewater treatment, both parental fipronil and the sum of fipronil-related compounds were removed in the wetland with efficiencies of 44 ± 4% and 47 ± 13%, respectively. Total fipronil concentrations in plant effluent (28 ± 6 ng/L as fipronil) were within an order of magnitude of half-maximal effective concentrations (EC50) of nontarget invertebrates. This is the first systematic assessment of the fate of fipronil and its major degradates during full-scale conventional wastewater and constructed wetland treatment.

Uptake of Neonicotinoid Insecticides by Water-Foraging Honey Bees (Hymenoptera: Apidae) Through Guttation Fluid of Winter Oilseed Rape

The water-foraging activity of honey bees (Apis mellifera L.) on guttation fluid of seed-coated crops, such as winter oilseed rape (WOR; Brassica napus L.), has not yet been evaluated. We analyzed the uptake of active substances (a.s.) in guttation fluid by evaluating residues of honey-sac contents. In autumn, insecticide residues of up to 130 µg a.s. per liter were released in WOR guttation fluid; this concentration is noticeably lower than levels reported in guttation fluid of seed-coated maize. Until winter dormancy, the concentrations declined to <30 µg a.s. per liter. In spring, residues were linked to prewintered plants and declined steadily until flowering. The maximum release of residues in guttation fluid of seed-coated WOR occurs on the first leaves in autumn when the colonies' water demand decreases. For the first time, proof for the uptake of guttation fluid from seed-coated WOR by honey bees was provided by measuring residues in individual honey-sac contents. In total, 38 out of 204 samples (19%) showed residues of thiamethoxam at concentrations ranging from 0.3 to 0.95 µg per liter while the corresponding concentrations in guttation fluid of WOR varied between 3.6 to 12.9 µg thiamethoxam per liter. The amounts of thiamethoxam we found in the honey sacs of water-foraging honey bees were therefore below the thresholds in nectar and pollen that are considered to have negative effects on honey bees after chronic exposure.

Effect of dietary supplementation of Bifidobacterium and Lactobacillus strains in Apis mellifera L. against Nosema ceranae

Nosema ceranae is a widespread microsporidium of European honeybee Apis mellifera L. affecting bee health. The ban of Fumagillin-B (dicyclohexylammonium salt) in the European Union has driven the search for sustainable strategies to prevent and control the infection. The gut microbial symbionts, associated to the intestinal system of vertebrates and invertebrates and its impact on host health, are receiving increasing attention. In particular, bifidobacteria and lactobacilli, which are normal inhabitants of the digestive system of bees, are known to protect their hosts via antimicrobial metabolites, immunomodulation and competition. In this work, the dietary supplementation of gut bacteria was evaluated under laboratory conditions in bees artificially infected with the parasite and bees not artificially infected but evidencing a low natural infection. Supplemented bacteria were selected among bifidobacteria, previously isolated, and lactobacilli, isolated in this work from healthy honeybee gut. Four treatments were compared: bees fed with sugar syrup (CTR); bees fed with sugar syrup containing bifidobacteria and lactobacilli (PRO); bees infected with N. ceranae spores and fed with sugar syrup (NOS); bees infected with N. ceranae and fed with sugar syrup containing bifidobacteria and lactobacilli (NP). The sugar syrup, with or without microorganisms, was administered to bees from the first day of life for 13 days. N. ceranae infection was carried out individually on anesthetised 5-day-old bees. Eight days after infection, a significant (P<0.05) lower level of N. ceranae was detected by real-time PCR in both NP and PRO group, showing a positive effect of supplemented microorganisms in controlling the infection. These results represent a first attempt of application of bifidobacteria and lactobacilli against N. ceranae in honeybees.

A Locomotor Deficit Induced by Sublethal Doses of Pyrethroid and Neonicotinoid Insecticides in the Honeybee Apis mellifera

The toxicity of pesticides used in agriculture towards non-targeted organisms and especially pollinators has recently drawn the attention from a broad scientific community. Increased honeybee mortality observed worldwide certainly contributes to this interest. The potential role of several neurotoxic insecticides in triggering or potentiating honeybee mortality was considered, in particular phenylpyrazoles and neonicotinoids, given that they are widely used and highly toxic for insects. Along with their ability to kill insects at lethal doses, they can compromise survival at sublethal doses by producing subtle deleterious effects. In this study, we compared the bee's locomotor ability, which is crucial for many tasks within the hive (e.g. cleaning brood cells, feeding larvae…), before and after an acute sublethal exposure to one insecticide belonging to the two insecticide classes, fipronil and thiamethoxam. Additionally, we examined the locomotor ability after exposure to pyrethroids, an older chemical insecticide class still widely used and known to be highly toxic to bees as well. Our study focused on young bees (day 1 after emergence) since (i) few studies are available on locomotion at this stage and (ii) in recent years, pesticides have been reported to accumulate in different hive matrices, where young bees undergo their early development. At sublethal doses (SLD48h, i.e. causing no mortality at 48 h), three pyrethroids, namely cypermethrin (2.5 ng/bee), tetramethrin (70 ng/bee), tau-fluvalinate (33 ng/bee) and the neonicotinoid thiamethoxam (3.8 ng/bee) caused a locomotor deficit in honeybees. While the SLD48h of fipronil (a phenylpyrazole, 0.5 ng/bee) had no measurable effect on locomotion, we observed high mortality several days after exposure, an effect that was not observed with the other insecticides. Although locomotor deficits observed in the sublethal range of pyrethroids and thiamethoxam would suggest deleterious effects in the field, the case of fipronil demonstrates that toxicity evaluation requires information on multiple endpoints (e.g. long term survival) to fully address pesticides risks for honeybees. Pyrethroid-induced locomotor deficits are discussed in light of recent advances regarding their mode of action on honeybee ion channels and current structure-function studies.

Effects of Oral Exposure to Fungicides on Honey Bee Nutrition and Virus Levels

Sublethal exposure to fungicides can affect honey bees (Apis mellifera L.) in ways that resemble malnutrition. These include reduced brood rearing, queen loss, and increased pathogen levels. We examined the effects of oral exposure to the fungicides boscalid and pyraclostrobin on factors affecting colony nutrition and immune function including pollen consumption, protein digestion, hemolymph protein titers, and changes in virus levels. Because the fungicides are respiratory inhibitors, we also measured ATP concentrations in flight muscle. The effects were evaluated in 3- and 7-d-old worker bees at high fungicide concentrations in cage studies, and at field-relevant concentrations in colony studies. Though fungicide levels differed greatly between the cage and colony studies, similar effects were observed. Hemolymph protein concentrations were comparable between bees feeding on pollen with and without added fungicides. However, in both cage and colony studies, bees consumed less pollen containing fungicides and digested less of the protein. Bees fed fungicide-treated pollen also had lower ATP concentrations and higher virus titers. The combination of effects we detected could produce symptoms that are similar to those from poor nutrition and weaken colonies making them more vulnerable to loss from additional stressors such as parasites and pathogens.

Transcriptomic profiling of host-parasite interactions in the microsporidian Trachipleistophora hominis

Background

Trachipleistophora hominis was isolated from an HIV/AIDS patient and is a member of a highly successful group of obligate intracellular parasites.

Methods

Here we have investigated the evolution of the parasite and the interplay between host and parasite gene expression using transcriptomics of T. hominis-infected rabbit kidney cells.

Results

T. hominis has about 30 % more genes than small-genome microsporidians. Highly expressed genes include those involved in growth, replication, defence against oxidative stress, and a large fraction of uncharacterised genes. Chaperones are also highly expressed and may buffer the deleterious effects of the large number of non-synonymous mutations observed in essential T. hominis genes. Host expression suggests a general cellular shutdown upon infection, but ATP, amino sugar and nucleotide sugar production appear enhanced, potentially providing the parasite with substrates it cannot make itself. Expression divergence of duplicated genes, including transporters used to acquire host metabolites, demonstrates ongoing functional diversification during microsporidian evolution. We identified overlapping transcription at more than 100 loci in the sparse T. hominis genome, demonstrating that this feature is not caused by genome compaction. The detection of additional transposons of insect origin strongly suggests that the natural host for T. hominis is an insect.

Conclusions

Our results reveal that the evolution of contemporary microsporidian genomes is highly dynamic and innovative. Moreover, highly expressed T. hominis genes of unknown function include a cohort that are shared among all microsporidians, indicating that some strongly conserved features of the biology of these enormously successful parasites remain uncharacterised.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1989-z) contains supplementary material, which is available to authorized users.

Evaluating sub-lethal effects of orchard-applied pyrethroids using video-tracking software to quantify honey bee behaviors

Managed honey bee, Apis mellifera L., colonies are contracted to pollinate fruit and nut orchards improving crop quality and yield. Colonies placed in orchards are potentially exposed to pyrethroid insecticides used for broad-spectrum pest control. Pyrethroids have been reported to pose minimal risk to bees due to their low application rates in the field and putative repellent properties. This repellency is believed to alter foraging behavior with the benefit of preventing bees from encountering a lethal dose in the field. However, sub-lethal exposure to pyrethroids may adversely impact bee behavior potentially resulting in social dysfunction or disruption of foraging. This study quantified behaviors associated with sub-lethal exposure to orchard-applied pyrethroids including, lambda-cyhalothrin, esfenvalerate, and permethrin, using video tracking software, Ethovision XT (Noldus Information Technologies). Bee locomotion, social interaction, and time spent near a food source were measured over a 24-h period. Bees treated with a pyrethroid traveled 30-71% less than control bees. Social interaction time decreased by 43% for bees treated with a high sub-lethal dose of esfenvalerate. Bees exposed to a high sub-lethal dose of permethrin spent 67% less time in social interaction and spent more than 5 times as long in the food zone compared to control bees.

In vitro effects of thiamethoxam on larvae of Africanized honey bee Apis mellifera (Hymenoptera: Apidae)

Several investigations have revealed the toxic effects that neonicotinoids can have on Apis mellifera, while few studies have evaluated the impact of these insecticides can have on the larval stage of the honeybee. From the lethal concentration (LC50) of thiamethoxam for the larvae of the Africanized honeybee, we evaluated the sublethal effects of this insecticide on morphology of the brain. After determine the LC50 (14.34 ng/μL of diet) of thiamethoxam, larvae were exposed to a sublethal concentration of thiamethoxam equivalent to 1.43 ng/μL by acute and subchronic exposure. Morphological and immunocytochemistry analysis of the brains of the exposed bees, showed condensed cells and early cell death in the optic lobes. Additional dose-related effects were observed on larval development. Our results show that the sublethal concentrations of thiamethoxam tested are toxic to Africanized honeybees larvae and can modulate the development and consequently could affect the maintenance and survival of the colony. These results represent the first assessment of the effects of thiamethoxam in Africanized honeybee larvae and should contribute to studies on honey bee colony decline.

Wings as a new route of exposure to pesticides in the honey bee

In pesticide risk assessment, estimating the routes and levels of exposure is critical. For honey bees subjected to pesticide spray, toxicity is assessed by thorax contact to account for all possible contact exposures. In the present study, the authors tested 6 active substances with different hydrophobicity. For the first time, the authors demonstrated that it is possible to induce mortality by pesticide contact with only the wings of the honey bee. The toxicities induced by contact with the wings and thorax were similar, with the wing median lethal dose (LD50) being 0.99 to 2.23 times higher than that of the thorax. This finding demonstrates that the wings represent a relevant route of exposure in the honey bee. In a second approach, the authors estimated the air volume displaced by the wings during 1 beating cycle to be 0.51 ± 0.03 cm(3), which corresponds to a volume of 116.8 ± 5.8 cm(3)  s(-1) at a wing beat frequency of 230 Hz. The authors then tested realistic scenarios of exposure for bees flying through a pesticide cloud at different concentrations. In the worst-case scenario, the dose accumulated during the flight reached 525 ng bee(-1)  s(-1). These results show that the procedure used to assess the risk posed by contact with pesticides could be improved by accounting for wing exposure.

Neonicotinoid Insecticides and Their Impacts on Bees: A Systematic Review of Research Approaches and Identification of Knowledge Gaps

It has been suggested that the widespread use of neonicotinoid insecticides threatens bees, but research on this topic has been surrounded by controversy. In order to synthesize which research approaches have been used to examine the effect of neonicotinoids on bees and to identify knowledge gaps, we systematically reviewed research on this subject that was available on the Web of Science and PubMed in June 2015. Most of the 216 primary research studies were conducted in Europe or North America (82%), involved the neonicotinoid imidacloprid (78%), and concerned the western honey bee Apis mellifera (75%). Thus, little seems to be known about neonicotinoids and bees in areas outside Europe and North America. Furthermore, because there is considerable variation in ecological traits among bee taxa, studies on honey bees are not likely to fully predict impacts of neonicotinoids on other species. Studies on crops were dominated by seed-treated maize, oilseed rape (canola) and sunflower, whereas less is known about potential side effects on bees from the use of other application methods on insect pollinated fruit and vegetable crops, or on lawns and ornamental plants. Laboratory approaches were most common, and we suggest that their capability to infer real-world consequences are improved when combined with information from field studies about realistic exposures to neonicotinoids. Studies using field approaches often examined only bee exposure to neonicotinoids and more field studies are needed that measure impacts of exposure. Most studies measured effects on individual bees. We suggest that effects on the individual bee should be linked to both mechanisms at the sub-individual level and also to the consequences for the colony and wider bee populations. As bees are increasingly facing multiple interacting pressures future research needs to clarify the role of neonicotinoids in relative to other drivers of bee declines.

Effects of Fungicide and Adjuvant Sprays on Nesting Behavior in Two Managed Solitary Bees, Osmia lignaria and Megachile rotundata

There is a growing body of empirical evidence showing that wild and managed bees are negatively impacted by various pesticides that are applied in agroecosystems around the world. The lethal and sublethal effects of two widely used fungicides and one adjuvant were assessed in cage studies in California on blue orchard bees, Osmia lignaria, and in cage studies in Utah on alfalfa leafcutting bees, Megachile rotundata. The fungicides tested were Rovral 4F (iprodione) and Pristine (mixture of pyraclostrobin + boscalid), and the adjuvant tested was N-90, a non-ionic wetting agent (90% polyethoxylated nonylphenol) added to certain tank mixtures of fungicides to improve the distribution and contact of sprays to plants. In separate trials, we erected screened cages and released 20 paint-marked females plus 30–50 males per cage to document the behavior of nesting bees under treated and control conditions. For all females in each cage, we recorded pollen-collecting trip times, nest substrate-collecting trip times (i.e., mud for O. lignaria and cut leaf pieces for M. rotundata), cell production rate, and the number of attempts each female made to enter her own or to enter other nest entrances upon returning from a foraging trip. No lethal effects of treatments were observed on adults, nor were there effects on time spent foraging for pollen and nest substrates and on cell production rate. However, Rovral 4F, Pristine, and N-90 disrupted the nest recognition abilities of O. lignaria females. Pristine, N-90, and Pristine + N-90 disrupted nest recognition ability of M. rotundata females. Electroantennogram responses of antennae of O. lignaria females maintained in the laboratory did not differ significantly between the fungicide-exposed and control bees. Our results provide the first empirical evidence that two commonly used fungicides and a non-ionic adjuvant can disrupt nest recognition in two managed solitary bee species.

Pesticides and pollinators: a context-sensitive policy approach

I examine recent policymaking efforts in the United States (US) that seek to improve how risks posed by pesticides to insect pollinators are assessed and managed. Utilizing the case of ongoing honey bee die-offs, I argue for a context-sensitive policy framework. From a scientific perspective, this entails not ignoring the uncertain knowledge emerging from laboratory and field studies regarding the indirect effects of low levels of certain insecticides in combination with other factors. From a social scientific perspective, policy initiatives to build partnerships between growers and beekeepers toward mitigating exposure to pesticides are crucial, and need to acknowledge barriers to the adoption of best management practices as well as a historically-established asymmetry between growers and beekeepers in the pollination industry.

Interactive effects of pesticide exposure and pathogen infection on bee health - a critical analysis

Bees are fundamentally important for pollination services and declines in populations could have significant economic and environmental implications. Pesticide exposure and pathogen infection are recognised as potential stressors impacting upon bee populations and recently there has been a surge in research on pesticide-disease interactions to reflect environmentally realistic scenarios better. We critically analyse the findings on pesticide-disease interactions, including effects on the survival, pathogen loads and immunity of bees, and assess the suitability of various endpoints to inform our mechanistic understanding of these interactions. We show that pesticide exposure and pathogen infection have not yet been found to interact to affect worker survival under field-realistic scenarios. Colony-level implications of pesticide effects on Nosema infections, viral loads and honey bee immunity remain unclear as these effects have been observed in a laboratory setting only using a small range of pesticide exposures, generally exceeding those likely to occur in the natural environment, and assessing a highly selected series of immune-related endpoints. Future research priorities include the need for a better understanding of pesticide effects on the antimicrobial peptide (AMP) component of an individual's immune response and on social defence behaviours. Interactions between pesticide exposure and bacterial and fungal infections have yet to be addressed. The paucity of studies in non-Apis bee species is a further major knowledge gap.

Nosema ceranae Can Infect Honey Bee Larvae and Reduces Subsequent Adult Longevity

Nosema ceranae causes a widespread disease that reduces honey bee health but is only thought to infect adult honey bees, not larvae, a critical life stage. We reared honey bee (Apis mellifera) larvae in vitro and provide the first demonstration that N. ceranae can infect larvae and decrease subsequent adult longevity. We exposed three-day-old larvae to a single dose of 40,000 (40K), 10,000 (10K), zero (control), or 40K autoclaved (control) N. ceranae spores in larval food. Spores developed intracellularly in midgut cells at the pre-pupal stage (8 days after egg hatching) of 41% of bees exposed as larvae. We counted the number of N. ceranae spores in dissected bee midguts of pre-pupae and, in a separate group, upon adult death. Pre-pupae exposed to the 10K or 40K spore treatments as larvae had significantly elevated spore counts as compared to controls. Adults exposed as larvae had significantly elevated spore counts as compared to controls. Larval spore exposure decreased longevity: a 40K treatment decreased the age by which 75% of adult bees died by 28%. Unexpectedly, the low dose (10K) led to significantly greater infection (1.3 fold more spores and 1.5 fold more infected bees) than the high dose (40K) upon adult death. Differential immune activation may be involved if the higher dose triggered a stronger larval immune response that resulted in fewer adult spores but imposed a cost, reducing lifespan. The impact of N. ceranae on honey bee larval development and the larvae of naturally infected colonies therefore deserve further study.

Dynamics of Apis mellifera Filamentous Virus (AmFV) Infections in Honey Bees and Relationships with Other Parasites

Apis mellifera filamentous virus (AmFV) is a large double stranded DNA virus of honey bees, but its relationship with other parasites and prevalence are poorly known. We analyzed individual honey bees from three colonies at different times post emergence in order to monitor the dynamics of the AmFV gut colonization under natural conditions. Prevalence and loads of microsporidia and trypanosomes were also recorded, as well as five common honey bee RNA viruses. The results show that a high proportion of bees get infected with AmFV during the first week post-emergence (75%) and that AmFV DNA levels remained constant. A similar pattern was observed for microsporidia while trypanosomes seem to require more time to colonize the gut. No significant associations between these three infections were found, but significant positive correlations were observed between AmFV and RNA viruses. In parallel, the prevalence of AmFV in France and Sweden was assessed from pooled honey bee workers. The data indicate that AmFV is almost ubiquitous, and does not seem to follow seasonal patterns, although higher viral loads were significantly detected in spring. A high prevalence of AmFV was also found in winter bees, without obvious impact on overwintering of the colonies.

Neonicotinoid-Coated Zea mays Seeds Indirectly Affect Honeybee Performance and Pathogen Susceptibility in Field Trials

Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads.

Effects, but no interactions, of ubiquitous pesticide and parasite stressors on honey bee (Apis mellifera) lifespan and behaviour in a colony environment

Interactions between pesticides and parasites are believed to be responsible for increased mortality of honey bee (Apis mellifera) colonies in the northern hemisphere. Previous efforts have employed experimental approaches using small groups under laboratory conditions to investigate influence of these stressors on honey bee physiology and behaviour, although both the colony level and field conditions play a key role for eusocial honey bees. Here, we challenged honey bee workers under in vivo colony conditions with sublethal doses of the neonicotinoid thiacloprid, the miticide tau-fluvalinate and the endoparasite Nosema ceranae, to investigate potential effects on longevity and behaviour using observation hives. In contrast to previous laboratory studies, our results do not suggest interactions among stressors, but rather lone effects of pesticides and the parasite on mortality and behaviour, respectively. These effects appear to be weak due to different outcomes at the two study sites, thereby suggesting that the role of thiacloprid, tau-fluvalinate and N. ceranae and interactions among them may have been overemphasized. In the future, investigations into the effects of honey bee stressors should prioritize the use of colonies maintained under a variety of environmental conditions in order to obtain more biologically relevant data.

Bee declines driven by combined stress from parasites, pesticides, and lack of flowers

Bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined; bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites accidentally spread by humans. Climate change is likely to exacerbate these problems in the future. Stressors do not act in isolation; for example, pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple interacting stressors is driving honey bee colony losses and declines of wild pollinators, but such interactions are not addressed by current regulatory procedures, and studying these interactions experimentally poses a major challenge. In the meantime, taking steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into farmland, reducing pesticide use through adopting more sustainable farming methods, and enforcing effective quarantine measures on bee movements are all practical measures that should be adopted. Effective monitoring of wild pollinator populations is urgently needed to inform management strategies into the future.

Fragmentation and management of Ethiopian moist evergreen forest drive compositional shifts of insect communities visiting wild Arabica coffee flowers

Coffea arabica is an indigenous understorey shrub of the moist evergreen Afromontane forest of SW Ethiopia. Coffee cultivation here occurs under different forest management intensities, ranging from almost no intervention in the 'forest coffee' system to far-reaching interventions that include the removal of competing shrubs and selective thinning of the upper canopy in the 'semi-forest coffee' system. We investigated whether increasing forest management intensity and fragmentation result in impacts upon potential coffee pollination services through examining shifts in insect communities that visit coffee flowers. Overall, we netted 2,976 insect individuals on C. arabica flowers, belonging to sixteen taxonomic groups, comprising 10 insect orders. Taxonomic richness of the flower-visiting insects significantly decreased and pollinator community changed with increasing forest management intensity and fragmentation. The relative abundance of honey bees significantly increased with increasing forest management intensity and fragmentation, likely resulting from the introduction of bee hives in the most intensively managed forests. The impoverishment of the insect communities through increased forest management intensity and fragmentation potentially decreases the resilience of the coffee production system as pollination increasingly relies on honey bees alone. This may negatively affect coffee productivity in the long term as global pollination services by managed honey bees are expected to decline under current climate change scenarios. Coffee agroforestry management practices should urgently integrate pollinator conservation measures.

Honey bee toxicology

Insecticides are chemicals used to kill insects, so it is unsurprising that many insecticides have the potential to harm honey bees (Apis mellifera). However, bees are exposed to a great variety of other potentially toxic chemicals, including flavonoids and alkaloids that are produced by plants; mycotoxins produced by fungi; antimicrobials and acaricides that are introduced by beekeepers; and fungicides, herbicides, and other environmental contaminants. Although often regarded as uniquely sensitive to toxic compounds, honey bees are adapted to tolerate and even thrive in the presence of toxic compounds that occur naturally in their environment. The harm caused by exposure to a particular concentration of a toxic compound may depend on the level of simultaneous exposure to other compounds, pathogen levels, nutritional status, and a host of other factors. This review takes a holistic view of bee toxicology by taking into account the spectrum of xenobiotics to which bees are exposed.

The effect of thiacloprid formulation on DNA/chromosome damage and changes in GST activity in bovine peripheral lymphocytes

The potential genotoxic effect of thiacloprid formulation on bovine peripheral lymphocytes was evaluated using the comet assay and the cytogenetic endpoints: chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei (MNi). Whole blood cultures were treated with the insecticide at concentrations of 30, 60, 120, 240 and 480 μg mL(-1) for 24, 48 h and/or 2 h of incubation. A statistically significant increase in the frequency of DNA damage, as well as in unstable chromosome aberrations (% breaks) were found after exposure to the insecticide at concentrations ranging from 120 to 480 μg mL(-1) (P < 0.05, P < 0.01, P < 0.001). For the detection of stable structural chromosome aberrations (e.g., translocations) and numerical aberrations by the FISH method, three whole chromosome painting probes for bovine chromosomes 1, 5 and 7 (BTA1, BTA5 and BTA7) were used in our experiments. We observed numerical aberrations, but without any statistical significance. Regarding the sister chromatid exchanges, no significant elevation in the SCE frequencies was found after 24-h exposure to the insecticide. A dose-related response in the SCE induction was obtained in bovine cultures after the prolonged time of exposure (48 h) to thiacloprid formulation at concentrations ranging from 120 to 480 μg mL(-1) in each donor (P < 0.05, P < 0.01), which was associated with a reduction of the PI (P < 0.05, P < 0.01). The insecticide failed to produce MNi; however, a significant reduction of CBPI was observed. Using real-time PCR, a decrease in the expression of bovine glutathione S-transferase M3 (GSTM3) was detected at the lowest dose. The higher concentrations of thiacloprid formulation caused an increase in the mRNA expression.

Effects of neonicotinoids and fipronil on non-target invertebrates

We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section "other invertebrates" review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large-scale and wide ranging negative biological and ecological impacts on a wide range of non-target invertebrates in terrestrial, aquatic, marine and benthic habitats.

Resistance of developing honeybee larvae during chronic exposure to dietary nicotine

The effects of pesticides on honeybee larvae are less understood than for adult bees, even though larvae are chronically exposed to pesticide residues that accumulate in comb and food stores in the hive. We investigated how exposure to a plant alkaloid, nicotine, affects survival, growth and body composition of honeybee larvae. Larvae of Apis mellifera scutellata were reared in vitro and fed throughout development on standard diets with nicotine included at concentrations from 0 to 1000μg/100g diet. Overall mortality across all nicotine treatments was low, averaging 9.8% at the prepupal stage and 18.1% at the white-eyed pupal stage, but survival was significantly reduced by nicotine. The mass of prepupae and white-eyed pupae was not affected by nicotine. In terms of body composition, nicotine affected water content but did not influence either protein or lipid stores of white-eyed pupae. We attribute the absence of consistent negative effects of dietary nicotine to detoxification mechanisms in developing honeybees, which enable them to resist both natural and synthetic xenobiotics.

Exploiting the architecture and the features of the microsporidian genomes to investigate diversity and impact of these parasites on ecosystems

Fungal species play extremely important roles in ecosystems. Clustered at the base of the fungal kingdom are Microsporidia, a group of obligate intracellular eukaryotes infecting multiple animal lineages. Because of their large host spectrum and their implications in host population regulation, they influence food webs, and accordingly, ecosystem structure and function. Unfortunately, their ecological role is not well understood. Present also as highly resistant spores in the environment, their characterisation requires special attention. Different techniques based on direct isolation and/or molecular approaches can be considered to elucidate their role in the ecosystems, but integrating environmental and genomic data (for example, genome architecture, core genome, transcriptional and translational signals) is crucial to better understand the diversity and adaptive capacities of Microsporidia. Here, we review the current status of Microsporidia in trophic networks; the various genomics tools that could be used to ensure identification and evaluate diversity and abundance of these organisms; and how these tools could be used to explore the microsporidian life cycle in different environments. Our understanding of the evolution of these widespread parasites is currently impaired by limited sampling, and we have no doubt witnessed but a small subset of their diversity.