The oral toxicity of the transgenic Bt+CpTI cotton pollen to honeybees (Apis mellifera)

The effect of Bt Cry9Ee toxin on honey bee brood and adults reared in vitro, Apis mellifera (Hymenoptera: Apidae)

The effects of Bt Cry9Ee toxin on honey bee, Apis mellifera L., survival, developmental rate, larval weight, pollen consumption, and midgut bacterial diversity were tested in the laboratory. Honey bee larvae and adults were reared in vitro and fed a diet that contained Cry9Ee toxin at 0.01, 0.1, 1, and 10 mg/L. Cry9Ee toxin 0.01, 0.1, and 1 mg/L in diet used in this study may represent a value closer to field relevance and the highest concentration is unlikely to be encountered in the field and thus represent a worst case scenario. The dependent variables were compared for groups of honey bees feeding on treated diet and those feeding on negative control (no addition of a test substance), solvent control (0.01 mM Na₂CO₃), and positive control diet (dimethoate 45 mg/L). Bt Cry9Ee toxin did not affect survival or larval weight, and the result was great confidence in accepting the null hypothesis by power analysis. The effect on development rates and pollen consumption were the inconclusive results because the post-hoc power was less than 0.8. Furthermore, the midgut bacterial structure and compositions were determined using high-throughput sequencing targeting the V3-V4 regions of the 16S rDNA. All core honey bee intestinal bacterial class such as γ-Proteobacteria, Actinobacteria, α-Proteobacteria, Bacilli, β-Proteobacteria, and Bacteroidia were detected, and no significant changes were found in the species diversity and richness between Cry9Ee treatments and laboratory control.

Transgenic Bt cotton expressing Cry1Ac/Cry2Ab or Cry1Ac/EPSPS does not affect the plant bug Adelphocoris suturalis or the pollinating beetle Haptoncus luteolus

The widespread cultivation of transgenic Bt cotton makes assessing the potential effects of this recombinant crop on non-target organisms a priority. However, the effect of Bt cotton on many insects is currently virtually unknown. The plant bug Adelphocoris suturalis is now a major pest of cotton in southern China and the beetle Haptoncus luteolus is one of the most ancient cotton pollinators. We conducted laboratory experiments to evaluate the toxicity of the Bt cotton varieties ZMSJ, which expresses the toxins Cry1Ac and Cry2Ab, and ZMKCKC, which expresses Cry1Ac and EPSPS, on adult A. suturalis and H. luteolus. No significant increase in the mortality of either species was detected after feeding on Bt cotton leaves or pollen for 7 days. Trace amounts of Cry1Ac and Cry2Ab proteins could be detected in both species but in vitro binding experiments found no evidence of Cry1Ac and Cry2Ab binding proteins. These results demonstrate that feeding on the leaves or pollen of these two Bt cotton varieties has no toxic effects on adult A. suturalis or H. luteolus.

Effects of Bt cabbage pollen on the honeybee Apis mellifera L

Honeybees may be exposed to insecticidal proteins from transgenic plants via pollen during their foraging activity. Assessing effects of such exposures on honeybees is an essential part of the risk assessment process for transgenic Bacillus thuringiensis (Bt) cabbage. Feeding trials were conducted in a laboratory setting to test for possible effects of Cry1Ba3 cabbage pollen on Italian-derived honeybees Apis mellifera L. Newly emerged A. mellifera were fed transgenic pollen, activated Cry1Ba3 toxin, pure sugar syrup (60% w/v sucrose solution), and non-transgenic cabbage pollen, respectively. Then the effects on survival, pollen consumption, weight, detoxification enzyme activity and midgut enzyme activity of A. mellifera were monitored. The results showed that there were no significant differences in survival, pollen consumption, weight, detoxification enzyme activity among all treatments. No significant differences in the activities of total proteolytic enzyme, active alkaline trypsin-like enzyme and weak alkaline trypsin-like enzyme were observed among all treatments. These results indicate that the side-effects of the Cry1Ba3 cabbage pollen on A. mellifera L. are unlikely.

Herbicide and insect resistant Bt cotton pollen assessment finds no detrimental effects on adult honey bees

One important concern regarding the use of transgenic cotton expressing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) is its potential detrimental effect on non-target organisms. The honey bee (Apis mellifera) is the most important pollinator species worldwide and it is directly exposed to transgenic crops by the consumption of genetically modified (GM) pollen. However, the potential effects of Bt cotton on A. mellifera remain unclear. In the present study, we assessed the effects of two Bt cotton varieties; ZMSJ expressing the Cry1Ac and Cry2Ab insecticidal proteins, and ZMKCKC producing Cry1Ac and EPSPS, on A. mellifera. Feeding on pollen from two Bt cotton varieties led to detection of low levels of Cry toxins (<10 ng/g fresh weight) in the midgut of A. mellifera adults, yet expression of detoxification genes did not change significantly compared to feeding on non-Bt cotton. Binding assays showed no Cry1Ac or Cry2Ab binding to midgut brush border membrane proteins from A. mellifera adults. Taken together, these results support minimal risk for potential negative effects on A. mellifera by exposure to Bt cotton.

The exposure of honey bees (Apis mellifera; Hymenoptera: Apidae) to pesticides: Room for improvement in research

Losses of honey bees have been repeatedly reported from many places worldwide. The widespread use of synthetic pesticides has led to concerns regarding their environmental fate and their effects on pollinators. Based on a standardised review, we report the use of a wide variety of honey bee matrices and sampling methods in the scientific papers studying pesticide exposure. Matrices such as beeswax and beebread were very little analysed despite their capacities for long-term pesticide storage. Moreover, bioavailability and transfer between in-hive matrices were poorly understood and explored. Many pesticides were studied but interactions between molecules or with other stressors were lacking. Sampling methods, targeted matrices and units of measure should have been, to some extent, standardised between publications to ease comparison and cross checking. Data on honey bee exposure to pesticides would have also benefit from the use of commercial formulations in experiments instead of active ingredients, with a special assessment of co-formulants (quantitative exposure and effects). Finally, the air matrix within the colony must be explored in order to complete current knowledge on honey bee pesticide exposure.

Ingestion of Bt rice pollen does not reduce the survival or hypopharyngeal gland development of Apis mellifera adults

Because of its ecological and economic importance, the honey bee Apis mellifera is commonly used to assess the environmental risk of insect-resistant, genetically modified plants. In the present study, feeding-exposure experiments were used to determine whether pollen from transgenic rice harms A. mellifera worker bees. In 1 experiment, the survival and mean acinus diameter of hypopharyngeal glands of adult bees were similar when bees were fed on pollen from Bt rice lines or from a non-Bt rice line, but bee survival was significantly reduced when they received pollen that was mixed with potassium arsenate as a positive control. In a second experiment, bee survival and hypopharyngeal gland development were not reduced when adult bees were fed on non-Bt pollen and a sucrose solution supplemented with Cry2A at 400 µg/g, Cry1C at 50 µg/g, or bovine serum albumin (BSA) at 400 µg/g, but bee survival and hypopharyngeal gland development were reduced when the diet was supplemented with soybean trypsin inhibitor as a positive control. In both experiments, the uptake of Cry proteins by adult bees was confirmed. Overall, the results indicate that the planting of Bt rice lines expressing Cry2A or Cry1C protein poses a negligible risk to A. mellifera worker bees. Environ Toxicol Chem 2017;36:1243-1248. © 2016 SETAC.

Bt Cry1Ie Toxin Does Not Impact the Survival and Pollen Consumption of Chinese Honey Bees, Apis cerana cerana (Hymenoptera, Apidae)

The cry1Ie gene may be a good candidate for the development of Bt maize because over-expression of Cry1Ie is highly toxic to Lepidopteran pests such as Heliothis armigera Hübner and Ostrinia furnacalis Guenée. The Bt cry1Ie gene also has no cross resistance with other insecticidal proteins such as Cry1Ab, Cry1Ac, Cry1Ah, or Cry1F. Chinese honey bees (Apis cerana cerana) are potentially exposed to insect-resistant genetically modified (IRGM) crops expressing Cry1Ie toxin via the collection of IRGM crop pollen. In this study, we tested whether Chinese honey bee workers are negatively affected by sugar syrup containing 20, 200, or 20,000 ng/ml Cry1Ie toxin and 48 ng/ml imidacloprid under controlled laboratory conditions. Our results demonstrated that the Cry1Ie toxin does not adversely impact survival and pollen consumption of Chinese honey bees. However, imidacloprid decreases Chinese honey bee survival and the total pollen consumption on the 5th, 6th, and 18th d of exposure. The described bioassay is suitable to assess the effects of GM expressed toxins against honey bee.

Bt Toxin Cry1Ie Causes No Negative Effects on Survival, Pollen Consumption, or Olfactory Learning in Worker Honey Bees (Hymenoptera: Apidae)

The honey bee ( Apis mellifera L.) is a key nontarget insect in environmental risk assessments of insect-resistant genetically modified crops. In controlled laboratory conditions, we evaluated the potential effects of Cry1Ie toxin on survival, pollen consumption, and olfactory learning of young adult honey bees. We exposed worker bees to syrup containing 20, 200, or 20,000 ng/ml Cry1Ie toxin, and also exposed some bees to 48 ng/ml imidacloprid as a positive control for exposure to a sublethal concentration of a toxic product. Results suggested that Cry1Ie toxin carries no risk to survival, pollen consumption, or learning capabilities of young adult honey bees. However, during oral exposure to the imidacloprid treatments, honey bee learning behavior was affected and bees consumed significantly less pollen than the control and Cry1Ie groups.

The effects of Bt Cry1Ie toxin on bacterial diversity in the midgut of Apis mellifera ligustica (Hymenoptera: Apidae)

The honey bee has been regarded as a key species in the environmental risk assessment of biotech crops. Here, the potential adverse effects of Cry1Ie toxin on the midgut bacteria of the worker bees (Apis mellifera ligustica) were investigated under laboratory conditions. Newly emerged bees were fed with different concentrations of Cry1Ie toxin syrups (20 ng/mL, 200 ng/mL, and 20 μg/mL), pure sugar syrup, and 48 ppb of imidacloprid syrups, then sampled after 15 and 30 d. We characterized the dominant midgut bacteria and compared the composition and structure of the midgut bacterial community in all samples using the Illumina MiSeq platform targeting the V3–V4 regions of 16S rDNA. No significant differences in the diversity of the midgut bacteria were observed between the five treatments. This work was the first to show the effects of Cry1Ie toxin on honey bees, and our study provided a theoretical basis for the biosafety assessment of transgenic Cry1Ie maize.

Comparison of the physiological characteristics of transgenic insect-resistant cotton and conventional lines

The introduction of transgenic insect-resistant cotton into agricultural ecosystems has raised concerns regarding its ecological effects. Many studies have been conducted to compare the differences in characteristics between transgenic cotton and conventional counterparts. However, few studies have focused on the different responses of transgenic cotton to stress conditions, especially to the challenges of pathogens. The aim of this work is to determine the extent of variation in physiological characteristics between transgenic insect-resistant cotton and the conventional counterpart infected by cotton soil-borne pathogens. The results showed that the difference in genetic backgrounds is the main factor responsible for the effects on biochemical characteristics of transgenic cotton when incubating with cotton Fusarium oxysporum. However, genetic modification had a significantly greater influence on the stomatal structure of transgenic cotton than the effects of cotton genotypes. Our results highlight that the differences in genetic background and/or genetic modifications may introduce variations in physiological characteristics and should be considered to explore the potential unexpected ecological effects of transgenic cotton.

Effects of transgenic Cry1Ac + CpTI cotton on non-target mealybug pest Ferrisia virgata and its predator Cryptolaemus montrouzieri

Recently, several invasive mealybugs (Hemiptera: Pseudococcidae) have rapidly spread to Asia and have become a serious threat to the production of cotton including transgenic cotton. Thus far, studies have mainly focused on the effects of mealybugs on non-transgenic cotton, without fully considering their effects on transgenic cotton and trophic interactions. Therefore, investigating the potential effects of mealybugs on transgenic cotton and their key natural enemies is vitally important. A first study on the effects of transgenic cotton on a non-target mealybug, Ferrisia virgata (Cockerell) (Hemiptera: Pseudococcidae) was performed by comparing its development, survival and body weight on transgenic cotton leaves expressing Cry1Ac (Bt toxin) + CpTI (Cowpea Trypsin Inhibitor) with those on its near-isogenic non-transgenic line. Furthermore, the development, survival, body weight, fecundity, adult longevity and feeding preference of the mealybug predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) was assessed when fed F. virgata maintained on transgenic cotton. In order to investigate potential transfer of Cry1Ac and CpTI proteins via the food chain, protein levels in cotton leaves, mealybugs and ladybirds were quantified. Experimental results showed that F. virgata could infest this bivalent transgenic cotton. No significant differences were observed in the physiological parameters of the predator C. montrouzieri offered F. virgata reared on transgenic cotton or its near-isogenic line. Cry1Ac and CpTI proteins were detected in transgenic cotton leaves, but no detectable levels of both proteins were present in the mealybug or its predator when reared on transgenic cotton leaves. Our bioassays indicated that transgenic cotton poses a negligible risk to the predatory coccinellid C. montrouzieri via its prey, the mealybug F. virgata.

Extraction, purification, and characterization of a trypsin inhibitor from cowpea seeds (Vigna unguiculata)

Protease inhibitors against trypsin were extracted from cowpea seeds, purified, and characterized. After the seed powder was defatted with hexane, the cowpea trypsin inhibitor (CpTI) was extracted with 0.15 M NaCl for 30 min. The crude extracts were then heated at 90°C for 10 min, followed by precipitation with 40-65% saturation ammonium sulfate, by which the protein purity increased approximately 15-fold. The CpTI had approximate 88-fold and 186-fold purification after anion-exchange chromatography (Super-Q) and gel filtration (Sephadex G-200), respectively. A broad band of the purified CpTI on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) indicates a degree of heterogeneity and partial denaturation of CpTI, having a molecular mass of ∼8000 kD. Multiple peaks between 7451 and 8898 by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy also suggest heterogeneity. The purified CpTI was stable at 90°C for 60 min, pH 5-10, and 0-3.0% of NaCl. The purification method described here can be used to obtain highly purified CpTI for its studies such as risk assessment of CpTI genetically modified foods.

Impact of single and stacked insect-resistant Bt-cotton on the honey bee and silkworm

Transgenic insect-resistant cotton (Bt cotton) has been extensively planted in China, but its effects on non-targeted insect species such as the economically important honey bee (Apis mellifera) and silkworm (Bombyx mori) currently are unknown. In this study, pollen from two Bt cotton cultivars, one expressing Cry1Ac/EPSPS and the other expressing Cry1Ac/Cry2Ab, were used to evaluate the effects of Bt cotton on adult honey bees and silkworm larvae. Laboratory feeding studies showed no adverse effects on the survival, cumulative consumption, and total hemocyte count (THC) of A. mellifera fed with Bt pollen for 7 days. No effects on the survival or development of B. mori larvae were observed either. A marginally significant difference between Cry1Ac/Cry2Ab cotton and the conventional cotton on the THC of the 3(rd) day of 5(th) B. mori instar larvae was observed only at the two highest pollen densities (approximately 900 and 8000 grains/cm(2)), which are much higher than the pollen deposition that occurs under normal field conditions. The results of this study show that pollen of the tested Bt cotton varieties carried no lethal or sublethal risk for A. mellifera, and the risk for B. mori was negligible.

A 2-year field study shows little evidence that the long-term planting of transgenic insect-resistant cotton affects the community structure of soil nematodes

Transgenic insect-resistant cotton has been released into the environment for more than a decade in China to effectively control the cotton bollworm (Helicoverpa armigera) and other Lepidoptera. Because of concerns about undesirable ecological side-effects of transgenic crops, it is important to monitor the potential environmental impact of transgenic insect-resistant cotton after commercial release. Our 2-year study included 1 cotton field where non-transgenic cotton had been planted continuously and 2 other cotton fields where transgenic insect-resistant cotton had been planted for different lengths of time since 1997 and since 2002. In 2 consecutive years (2009 and 2010), we took soil samples from 3 cotton fields at 4 different growth stages (seedling, budding, boll-forming and boll-opening stages), collected soil nematodes from soil with the sugar flotation and centrifugation method and identified the soil nematodes to the genus level. The generic composition, individual densities and diversity indices of the soil nematodes did not differ significantly between the 2 transgenic cotton fields and the non-transgenic cotton field, but significant seasonal variation was found in the individual densities of the principal trophic groups and in the diversity indices of the nematodes in all 3 cotton fields. The study used a comparative perspective to monitor the impact of transgenic insect-resistant cotton grown in typical ‘real world’ conditions. The results of the study suggested that more than 10 years of cultivation of transgenic insect-resistant cotton had no significant effects–adverse or otherwise–on soil nematodes. This study provides a theoretical basis for ongoing environmental impact monitoring of transgenic plants.

Effect of stacked insecticidal Cry proteins from maize pollen on nurse bees (Apis mellifera carnica) and their gut bacteria

Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees.

Electrogenerated chemiluminescence immunosensor for Bacillus thuringiensis Cry1Ac based on Fe3O4@Au nanoparticles

A highly sensitive electrochemiluminescence (ECL) immunosensor for Cry1Ac was fabricated. The primary antibody anti-Cry1Ac was immobilized onto core-shell structural Fe(3)O(4)@Au nanoparticles. The antigen and glucose-oxidase-labeled secondary antibody were then successively combined to form sandwich-type immunocomplexes through a specific interaction. The magnetic particles loaded with sandwich immune complexes were attracted to a magnet-controlled glass carbon electrode (GCE) by an external magnet applied on top of the GCE. ECL was generated by the reaction between luminol and hydrogen peroxide derived from the enzymatic reaction in the presence of glucose. The sensors exhibited high sensitivity and a wide linear range for Bacillus thuringiensis Cry1Ac detection from 0 to 6 ng/mL, as well as a detection limit of 0.25 pg/mL (S/N = 3). The sensor is one of the most sensitive sensors for Cry1Ac, which can be easily renewed and conveniently used.

Does transgenic Cry1Ac + CpTI cotton pollen affect hypopharyngeal gland development and midgut proteolytic enzyme activity in the honey bee Apis mellifera L. (Hymenoptera, Apidae)?

The transgenic Cry1Ac (Bt toxin) + CpTI (Cowpea Trypsin Inhibitor) cotton cultivar CCRI41 is increasingly used in China and potential side effects on the honey bee Apis mellifera L. have been documented recently. Two studies have assessed potential lethal and sublethal effects in young bees fed with CCRI41 cotton pollen but no effect was observed on learning capacities, although lower feeding activity in exposed honey bees was noted (antifeedant effect). The present study aimed at providing further insights into potential side effects of CCRI41 cotton on honey bees. Emerging honey bees were exposed to different pollen diets using no-choice feeding protocols (chronic exposure) in controlled laboratory conditions and we aimed at documenting potential mechanisms underneath the CCRI41 antifeedant effect previously reported. Activity of midgut proteolytic enzyme of young adult honey bees fed on CCRI41 cotton pollen were not significantly affected, i.e. previously observed antifeedant effect was not linked to disturbed activity of the proteolytic enzymes in bees' midgut. Hypopharyngeal gland development was assessed by quantifying total extractable proteins from the glands. Results suggested that CCRI41 cotton pollen carries no risk to hypopharyngeal gland development of young adult honey bees. In the two bioassays, honey bees exposed to 1 % soybean trypsin inhibitor were used as positive controls for both midgut proteolytic enzymes and hypopharyngeal gland proteins quantification, and bees exposed to 48 ppb (part per billion) (i.e. 48 ng g(-1)) imidacloprid were used as controls for exposure to a sublethal concentration of toxic product. The results show that the previously reported antifeedant effect of CCRI41 cotton pollen on honey bees is not linked to effects on their midgut proteolytic enzymes or on the development of their hypopharyngeal glands. The results of the study are discussed in the framework of risk assessment of transgenic crops on honey bees.

Field assessment of Bt cry1Ah corn pollen on the survival, development and behavior of Apis mellifera ligustica

Honeybees may be exposed to insecticidal proteins from transgenic plants via pollen. An assessment of the impact of such exposures on the honeybee is an essential part of the risk assessment process for transgenic Bacillus thuringiensis corn. A field trial was conducted to evaluate the effect of transgenic Bt cry1Ah corn on the honeybee Apis mellifera ligustica. Colonies of honeybees were moved to Bt or non-Bt corn fields during anthesis and then sampled to record their survival, development and behavior. No differences in immature stages, worker survival, bee body weight, hypopharyngeal gland weight, colony performance, foraging activity or olfactory learning abilities were detected between colonies that were placed in non-Bt corn fields and those placed in Bt corn fields. We conclude that cry1Ah corn carries no risk for the survival, development, colony performance or behavior of the honeybee A. mellifera ligustica.

Risk assessment and ecological effects of transgenic Bacillus thuringiensis crops on non-target organisms

The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.

Use of an innovative T-tube maze assay and the proboscis extension response assay to assess sublethal effects of GM products and pesticides on learning capacity of the honey bee Apis mellifera L

Transgenic Cry1Ac+CpTI cotton (CCRI41) is a promising cotton cultivar throughout China but side effects and especially sublethal effects of this transgenic cultivar on beneficial insects remain poorly studied. More specifically potential sublethal effects on behavioural traits of the honey bee Apis mellifera L. have not been formally assessed despite the importance of honey bees for pollination. The goal of our study was to assess potential effects of CCRI41 cotton pollen on visual and olfactory learning by honey bees. After a 7-day oral chronic exposure to honey mixed with either CCRI41 pollen, imidacloprid-treated conventional pollen (used as positive sublethal control) or conventional pollen (control), learning performance was evaluated by the classical proboscis extension reflex (PER) procedure as well as a T-tube maze test. The latter assay was designed as a new device to assess potential side effects of pesticides on visual associative learning of honey bees. These two procedures were complementary because the former focused on olfactory learning while the latter was involved in visual learning based on visual orientation ability. Oral exposure to CCRI41 pollen did not affect learning capacities of honey bees in both the T-tube maze and PER tests. However, exposure to imidacloprid resulted in reduced visual learning capacities in T-tube maze evaluation and decreased olfactory learning performances measured with PER. The implications of these results are discussed in terms of risks of transgenic CCRI41 cotton crops for honey bees.

Quantification of toxins in a Cry1Ac + CpTI cotton cultivar and its potential effects on the honey bee Apis mellifera L

Transgenic Cry1Ac + CpTI cotton (CCRI41) is increasingly planted throughout China. However, negative effects of this cultivar on the honey bee Apis mellifera L., the most important pollinator for cultivated ecosystem, remained poorly investigated. The objective of our study was to evaluate the potential side effects of transgenic Cry1Ac + CpTI pollen from cotton on young adult honey bees A. mellifera L. Two points emphasized the significance of our study: (1) A higher expression level of insecticidal protein Cry1Ac in pollen tissues was detected (when compared with previous reports). In particular, Cry1Ac protein was detected at 300 ± 4.52 ng g(-1) [part per billion (ppb)] in pollen collected in July, (2) Effects on chronic mortality and feeding behaviour in honey bees were evaluated using a no-choice dietary feeding protocol with treated pollen, which guarantee the highest exposure level to bees potentially occurring in natural conditions (worst case scenario). Tests were also conducted using imidacloprid-treated pollen at a concentration of 48 ppb as positive control for sublethal effect on feeding behaviour. Our results suggested that Cry1Ac + CpTI pollen carried no lethal risk for honey bees. However, during a 7-day oral exposure to the various treatments (transgenic, imidacloprid-treated and control), honey bee feeding behaviour was disturbed and bees consumed significantly less CCRI41 cotton pollen than in the control group in which bees were exposed to conventional cotton pollen. It may indicate an antifeedant effect of CCRI41 pollen on honey bees and thus bees may be at risk because of large areas are planted with transgenic Bt cotton in China. This is the first report suggesting a potential sublethal effect of CCRI41 cotton pollen on honey bees. The implications of the results are discussed in terms of risk assessment for bees as well as for directions of future work involving risk assessment of CCRI41 cotton.