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Exposure to pesticides may jeopardize pollinators, but it has rarely been examined in urban landscapes. We used larval food provisions (mix of pollen and nectar) of mason bees (Osmia spp.) nested in artificial shelters as matrices to investigate the rate of pesticide pollution in twelve allotment sites in Prague and Brno cities. Seven commercial croplands (fruit orchards, oilseed rape fields) were selected for comparison. In total, 79 samples of larval provisions were analysed using a validated UPLC–MS/MS method for the presence of 262 pesticides and/or important metabolites. Fifty-six pesticide residues were detected in the allotments and 74 in cropland sites. Fifty pesticide compounds were common to both landscapes. Fewer residues were found in the allotments (14.3 ± 0.9, mean ± SE) than in croplands (21.5 ± 1.1, mean ± SE; df = 17.4; t = −2.9; p < 0.01), and they were present at low levels up to 16 ppb. In cropland sites, ten residues occurred at high individual concentrations (mean per site > 10 ppb). The highest levels were observed for the fungicide pyrimethanil (mean = 1,989 ppb, maximum = 3,983 ppb) and among insecticides for thiacloprid (mean = 136 ppb, maximum = 170 ppb). The results supported the presumption of a lower risk of pesticide exposure in urban gardens than in croplands. Given the limited knowledge on the sublethal effects of pesticides and especially pesticide mixtures on solitary bee development, the regulation or control of pesticide use in allotment gardens is recommended. [ABSTRACT FROM AUTHOR]

Simple Summary: In recent decades, there has been a significant global decline in pollinators. In addition to the honey bee, it is bumblebees that contribute significantly to the pollination of many wild and farm plants. Many factors, such as habitat loss, climate change, pesticides and pathogens, are contributing to the decline of bumblebee populations. The main parasites of bumblebees include Crithidia bombi, Apicystis bombi and Nosema bombi. In our study, we aimed to obtain the first knowledge of their occurrence in the Czech Republic in the two most abundant bumblebee species (buff-tailed bumblebee Bombus terrestris and red-tailed bumblebee Bombus lapidarius). More than half of the captured buff-tailed bumblebee individuals were infected by C. bombi, less than a quarter of N. bombi individuals and the least by A. bombi. Red-tailed bumblebee individuals were infected less frequently. Surprisingly, more individuals were infected with all three parasite species than with only the combination of N. bombi and A. bombi. Parasite infection is also influenced by the environment. More individuals were infected with C. bombi in urban and forested landscapes than in grasslands and agricultural landscapes. In turn, a higher incidence of N. bombi was found around greenhouses where commercially produced bumblebees were used. Bumblebees are significant pollinators for both wild plants and economically important crops. Due to the worldwide decrease in pollinators, it is crucial to monitor the prevalence and distribution of bumblebee pathogens. Field-caught bumblebee workers and males were examined for the presence of three pathogens during the summer months of the years 2015–2020 (Bombus terrestris/lucorum) and 2015–2017 (Bombus lapidarius). The greatest prevalence was in the case of Crithidia bombi, where significantly more workers (57%) of B. terrestris/lucorum were infected than males (41%). Infection was also confirmed in 37% of B. lapidarius workers. The average prevalence was very similar in the case of Nosema bombi in workers (25%) and males (22%) of B. terrestris/lucorum. In the case of B. lapidarius, 17% of the workers were infected. The lowest number of infected individuals was for Apicystis bombi and the prevalence of infection was significantly higher for males (22%) than workers (8%) of B. terrestris/lucorum. Only 3% of workers and 4% of males of B. terrestris/lucorum were simultaneously infected with three types of pathogens, but no worker was infected with only a combination of N. bombi and A. bombi. The greatest prevalence of C. bombi was found in urban or woodland areas. [ABSTRACT FROM AUTHOR]

Solitary bees pollinate wild plants and crops. In the temperate zone, they mainly pollinate fruit trees. Most species nest in the soil, but mason bees nest in wooden cavities above ground. Their presence in orchards can be augmented by provision of artificial nesting sites. Two species of mason bees frequently use these artificial nesting opportunities in Central Europe. The red mason bee (Osmia bicornis) is the most common species in this region, which preferentially collects pollen from oak trees. The European orchard bee (Osmia cornuta) prefers pollen from fruit trees, but it is more thermophilic. Its spread to higher altitudes can be expected in response to climate change. A breeding technology based on detachable wooden nests is summarized in this paper based on a literature review and experimental experience in fruit orchards in Czechia. [ABSTRACT FROM AUTHOR]

Understanding the social evolution leading to insect eusociality requires, among other, a detailed insight into endocrine regulatory mechanisms that have been co-opted from solitary ancestors to play new roles in the complex life histories of eusocial species. Bumblebees represent well-suited models of a relatively primitive social organization standing on the mid-way to highly advanced eusociality and their queens undergo both, a solitary and a social phase, separated by winter diapause. In the present paper, we characterize the gene expression levels of major endocrine regulatory pathways across tissues, sexes, and life-stages of the buff-tailed bumblebee, Bombus terrestris, with special emphasis on critical stages of the queen's transition from solitary to social life. We focused on fundamental genes of three pathways: (1) Forkhead box protein O and insulin/insulin-like signaling, (2) Juvenile hormone (JH) signaling, and (3) Adipokinetic hormone signaling. Virgin queens were distinguished by higher expression of forkhead box protein O and downregulated insulin-like peptides and JH signaling, indicated by low expression of methyl farnesoate epoxidase (MFE) and transcription factor Krüppel homolog 1 (Kr-h1). Diapausing queens showed the expected downregulation of JH signaling in terms of low MFE and vitellogenin (Vg) expressions, but an unexpectedly high expression of Kr-h1. By contrast, reproducing queens revealed an upregulation of MFE and Vg together with insulin signaling. Surprisingly, the insulin growth factor 1 (IGF-1) turned out to be a queen-specific hormone. Workers exhibited an expression pattern of MFE and Vg similar to that of reproducing queens. Males were characterized by high Kr-h1 expression and low Vg level. The tissue comparison unveiled an unexpected resemblance between the fat body and hypopharyngeal glands across all investigated genes, sexes, and life stages. [ABSTRACT FROM AUTHOR]

Insects’ fat bodies are responsible for nutrient storage and for a significant part of intermediary metabolism. Thus, it can be expected that the structure and content of the fat body will adaptively change, if an insect is going through different life stages. Bumblebee queens belong to such insects as they dramatically change their physiology several times over their lives in relation to their solitary overwintering, independent colony foundation stage, and during the colony life-cycle ending in the senescent stage. Here, we report on changes in the ultrastructure and lipid composition of the peripheral fat body of Bombus terrestris queens in relation to seasonal changes in the queens’ activity. Six life stages are defined and evaluated in particular: pharate, callow, before and after hibernation, egg-laying, and senescence. Transmission electron microscopy revealed that the fat body contained two main cell types–adipocytes and oenocytes. Only adipocytes reveal important changes related to the life phase, and mostly the ration between inclusion and cytoplasm volume varies among particular stages. Both electron microscopy and chemical analyses of lipids highlighted seasonal variability in the quantity of the stored lipids, which peaked prior to hibernation. Triacylglycerols appeared to be the main energy source during hibernation, while the amount of glycogen before and after hibernation remained unchanged. In addition, we observed that the representation of some fatty acids within the triacylglycerols change during the queen’s life. Last but not least, we show that fat body cell membranes do not undergo substantial changes concerning phospholipid composition in relation to overwintering. This finding supports the hypothesis that the cold-adaptation strategy of bumblebee queens is more likely to be based on polyol accumulation than on the restructuring of lipid membranes. [ABSTRACT FROM AUTHOR]

Two-dimensional comprehensive gas chromatography (GC×GC) coupled with mass detection was used as a tool for biosynthetic studies of bumblebee pheromones. Prior to biosynthetic experiments, the chromatographic behaviour of isotopically modified esters in the GC×GC system as well as their behaviour in mass detection was studied. The male marking pheromones of Bombus lucorum, Bombus lapidarius and Bombus terrestris were investigated. Main pheromonal components are ethyl tetradec-9-enoate (53 %) and ethyl dodecanoate (6 %) in B. lucorum, hexadec-9-en-1-ol (52 %) and hexadecan-1-ol (31 %) in B. lapidarius, and 2,3-dihydrofarnesol (58 %) and ethyl dodecanoate (15 %) in B. terrestris. The research strategy was based on 1) in vivo incubation of isotopically (2H, 13C) modified fatty acids (FAs) and analysis of their metabolites and 2) feeding experiments with 2H- and 13C-labelled FAs mixed with food. It was observed that labelled FAs were modified into the most abundant aliphatic compounds present in labial gland secretions. In feeding experiments, the labelled FAs were transformed into pheromone components. Transport of the FA precursors from the fat body through haemolymph was confirmed. The results show that FAs, stored in the form of triacylglycerols in the fat body, are likely to participate in the biosynthesis of some aliphatic pheromone components. [ABSTRACT FROM AUTHOR]

Domestic gardens supply pollinators with valuable habitats, but the risk of exposure to pesticides has been little investigated. Artificial nesting shelters of a red mason bee species (Osmia bicornis) were placed in two suburban gardens and two commercial fruit orchards to determine the contamination of forage sources by pesticides. Larval pollen provisions were collected from a total of 14 nests. They consisted mainly of pollen from oaks (65–100% weight/sample), Brassicaceae (≤34% w/s) and fruit trees (≤1.6% w/s). Overall, 30 pesticides were detected and each sample contained a mixture of 11–21 pesticide residues. The pesticide residues were significantly lower in garden samples than in orchard samples. The difference was attributed mainly to the abundant fungicides pyrimethanil and boscalid, which were sprayed in fruit orchards and were present on average at 1004 ppb and 648 ppb in orchard samples, respectively. The results suggested that pollinators can benefit from domestic gardens by foraging from floral sources less contaminated by pesticides than in adjacent croplands. [ABSTRACT FROM AUTHOR]

Bumble bees are important pollinators broadly used by farmers in greenhouses and under conditions in which honeybee pollination is limited. As such, bumble bees are increasingly being reared for commercial purposes, which brings into question whether individuals reared under laboratory conditions are fully capable of physiological adaptation to field conditions. To understand the changes in bumble bee organism caused by foraging, we compared the fundamental physiological and immunological parameters of Bombus terrestris workers reared under constant optimal laboratory conditions with workers from sister colonies that were allowed to forage for two weeks in the field. Nutritional status and immune response were further determined in wild foragers of B.terrestris that lived under the constant influence of natural stressors. Both wild and laboratory-reared workers subjected to the field conditions had a lower protein concentration in the hemolymph and increased antimicrobial activity, the detection of which was limited in the non-foragers. However, in most of the tested parameters, specifically the level of carbohydrates, antioxidants, total hemocyte concentration in the hemolymph and melanization response, we did not observe any significant differences between bumble bee workers produced in the laboratory and wild animals, nor between foragers and non-foragers. Our results show that bumble bees reared under laboratory conditions can mount a sufficient immune response to potential pathogens and cope with differential food availability in the field, similarly to the wild bumble bee workers. [ABSTRACT FROM AUTHOR]