In agricultural landscapes honeybees and other pollinators are exposed to pesticides, often surveyed by residue analysis of bee bread. However, bee bread is a mixture of pollen pellets of different plants collected over a longer time period. Therefore, pesticide content in the hive varies with plant species and time of pollen collection. Hence, the analysis of bee bread is an approximate approach to gain information on detailed pesticide exposure during the agronomic active season. As high-resolution data is missing, we carried out a pesticide residue survey over five years (2012–2016) of daily collected pollen pellets at three agricultural distinct sites in southern Germany. 281 single day pollen samples were selected and subjected to a multi-pesticide residue analysis. Pesticide contaminations of pollen differed between the sites. Intensive pesticide exposure can be seen by high pesticide concentrations as well as a high amount of different pesticides detected. During the five years of observation 73 different pesticides were found, of which 84% are characterized as non-harmful to honeybees. To estimate pesticide risks for honeybees, the pollen hazard quotient (PHQ) was calculated. Even though pesticides were detected in sublethal concentrations, we found substances not supposed to be exposed to honey bees, indicating the necessity for further improvement of seed treatments and increasing awareness of flowering shrubs, field margins and pesticide drift. Additionally, an in-depth analysis of nine pollen samples, divided into sub-fractions dominated by single plant species, revealed even higher concentrations in single crops for some pesticides. We give precise residue data of 1,657 single pesticide detections, which should be used for realistic laboratory and field tests.
The contamination of bee products, e.g., bee bread, by pesticides is an increasing problem of beekeeping in rural areas. Bee bread is used by nurse bees to produce larval food. However, the fate of pesticides originating from the pollen during this process is unknown. Over the entire period of queen rearing, adult honeybees in queenless mini-hives were fed with a pollen-honey diet containing a cocktail of 13 commonly used pesticides in high concentrations (34-920 μg/kg). Royal jelly (RJ) harvested from queen cells was subjected to a multi-residue analysis. Seven substances were rediscovered in traces (76.5% of all detections are below 1 μg/kg) with at most 0.016% of the original pesticide concentrations of the fed diet. Considering this extraordinary low contamination of RJ, it seems unlikely that pesticides, if used according to the approved application instructions, would impair the development and health of honeybee queens. Possible reasons for the low residue levels in RJ are discussed.
The intestinal microbiota of honey bees consists of only few bacterial species and may have effects on health and pathogen resilience. Honey is usually harvested and replaced by sugar syrup. We hypothesized that replacing honey may change the composition of the intestinal microbiota, and therefore compromise pathogen resilience. Fifteen colonies were fed with wheat starch syrup, sucrose syrup, or blossom honey. 16S-based bacterial community analysis was performed on three individuals per hive in summer and winter, and Nosema ceranae and Crithidia /Lotmaria levels were assessed by qPCR. Seasonal differences in the intestinal microbiota and N. ceranae were found; however, microbiota and parasite levels were very similar between the feed types. Rhizobiales and Bifidobacteria were found to be increased in the bees that had received honey or wheat starch syrup, as compared to sucrose syrup. In conclusion, intestinal microbiota and parasites were found to be largely unaffected by the winter feed type.
Pollen might be contaminated by multiple pesticides representing a risk for long-term contamination of honeybees when collected. Standardized methodology to assess the effects of pesticide mixtures under field conditions is lacking. We conducted an experiment on chronic feeding of a diet contaminated with a field-realistic pesticide mixture on free-flying honeybee colonies. Pesticide residues in larvae and adult tagmata were detected in trace amounts. In colonies treated with a pesticide mixture, larval weight was higher and acini diameters of the hypopharyngeal glands of nurse bees were smaller than in the untreated control. Brood termination and adult lifespan did not differ between both groups. Our study offers a reproducible and applicable approach for testing effects of pesticides on bee health. As feeding of a field-realistic pesticide mixture did not elicit acute bee toxic effects, the described differences might be explained by sub-lethal effects or joint action of single compounds. pesticide combination / field test / long-term uptake / mini hives / multi-residue analysis Electronic supplementary material The online version of this article (
Introduction Smokers discount delayed rewards steeper than non-smokers or ex-smokers, possibly due to neuropharmacological effects of tobacco on brain circuitry, or lower abstinence rates in smokers with steep discounting. To delineate both theories from each other, we tested if temporal discounting, choice inconsistency, and related brain activity in treatment-seeking smokers (1) are higher compared to non-smokers, (2) decrease after smoking cessation, and (3) predict relapse. Methods At T1, 44 dependent smokers, 29 non-smokers, and 30 occasional smokers underwent fMRI while performing an intertemporal choice task. Smokers were measured before and 21 days after cessation if abstinent from nicotine. In total, 27 smokers, 28 non-smokers, and 29 occasional smokers were scanned again at T2. Discounting rate k and inconsistency var(k) were estimated with Bayesian analysis. Results First, k and var(k) in smokers in treatment were not higher than in non-smokers or occasional smokers. Second, neither k nor var(k) changed after smoking cessation. Third, k did not predict relapse, but high var(k) was associated with relapse during treatment and over 6 months. Brain activity in valuation and decision networks did not significantly differ between groups and conditions. Conclusion Our data from treatment-seeking smokers do not support the pharmacological hypothesis of pronounced reversible changes in discounting behavior and brain activity, possibly due to limited power. Behavioral data rather suggest that differences between current and ex-smokers might be due to selection. The association of choice consistency and treatment outcome possibly links consistent intertemporal decisions to remaining abstinent.
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