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Wueppenhorst K, Alkassab AT, Beims H, Ernst U, Friedrich E, Illies I, Janke M, Kirchner WH, Seidel K, Steinert M, Yurkov A, Erler S, Odemer R. Honey bee colonies can buffer short-term stressor effects of pollen restriction and fungicide exposure on colony development and the microbiome. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 282:116723. [PMID: 39024947 DOI: 10.1016/j.ecoenv.2024.116723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 07/04/2024] [Accepted: 07/09/2024] [Indexed: 07/20/2024]
Abstract
Honey bees (Apis mellifera) have to withstand various environmental stressors alone or in combination in agriculture settings. Plant protection products are applied to achieve high crop yield, but residues of their active substances are frequently detected in bee matrices and could affect honey bee colonies. In addition, intensified agriculture could lead to resource limitation for honey bees. This study aimed to compare the response of full-sized and nucleus colonies to the combined stressors of fungicide exposure and resource limitation. A large-scale field study was conducted simultaneously at five different locations across Germany, starting in spring 2022 and continuing through spring 2023. The fungicide formulation Pictor® Active (active ingredients boscalid and pyraclostrobin) was applied according to label instructions at the maximum recommended rate on oil seed rape crops. Resource limitation was ensured by pollen restriction using a pollen trap and stressor responses were evaluated by assessing colony development, brood development, and core gut microbiome alterations. Furthermore, effects on the plant nectar microbiome were assessed since nectar inhabiting yeast are beneficial for pollination. We showed, that honey bee colonies were able to compensate for the combined stressor effects within six weeks. Nucleus colonies exposed to the combined stressors showed a short-term response with a less favorable brood to bee ratio and reduced colony development in May. No further impacts were observed in either the nucleus colonies or the full-sized colonies from July until the following spring. In addition, no fungicide-dependent differences were found in core gut and nectar microbiomes, and these differences were not distinguishable from local or environmental effects. Therefore, the provision of sufficient resources is important to increase the resilience of honey bees to a combination of stressors.
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Affiliation(s)
- Karoline Wueppenhorst
- Institute for Bee Protection, Julius Kuehn-Institute, Messeweg 11-12, Braunschweig 38104, Germany; Zoological Institute, Technische Universität Braunschweig, Mendelsohnstraße 4, Braunschweig 38106, Germany.
| | - Abdulrahim T Alkassab
- Institute for Bee Protection, Julius Kuehn-Institute, Messeweg 11-12, Braunschweig 38104, Germany
| | - Hannes Beims
- Fachberatung für Imkerei, Bezirk Oberbayern, Prinzregentenstraße 14, München 80538, Germany; Institute for Apicuture, Lower Saxony State Office for Consumer Protection and Food Safety, Herzogin-Eleonore-Allee 5, Celle 29221, Germany
| | - Ulrich Ernst
- State Institute of Bee Research, University of Hohenheim, Erna-Hruschka-Weg 6, Stuttgart 70599, Germany; KomBioTa - Center for Biodiversity and Integrative Taxonomy, University of Hohenheim, Stuttgart, Germany
| | - Elsa Friedrich
- State Institute of Bee Research, University of Hohenheim, Erna-Hruschka-Weg 6, Stuttgart 70599, Germany
| | - Ingrid Illies
- Institute for Bee Research and Beekeeping, Bavarian State Institute for Viticulture and Horticulture, An der Steige 15, Veitshöchheim 97209, Germany
| | - Martina Janke
- Institute for Apicuture, Lower Saxony State Office for Consumer Protection and Food Safety, Herzogin-Eleonore-Allee 5, Celle 29221, Germany
| | - Wolfgang H Kirchner
- Behavioral Biology and Biology Education, Ruhr-University-Bochum, Universitätsstraße 150, Bochum 44780, Germany
| | - Kim Seidel
- Institute for Apicuture, Lower Saxony State Office for Consumer Protection and Food Safety, Herzogin-Eleonore-Allee 5, Celle 29221, Germany
| | - Michael Steinert
- Institute for Microbiology, Technische Universität Braunschweig, Spielmannstraße 7, Braunschweig 38106, Germany
| | - Andrey Yurkov
- DSMZ-German Collection of Microorganisms and Cell Cultures GmbH, Leibnitz Institute, Inhoffenstraße 7b, Braunschweig 38124, Germany
| | - Silvio Erler
- Institute for Bee Protection, Julius Kuehn-Institute, Messeweg 11-12, Braunschweig 38104, Germany; Zoological Institute, Technische Universität Braunschweig, Mendelsohnstraße 4, Braunschweig 38106, Germany
| | - Richard Odemer
- Institute for Bee Protection, Julius Kuehn-Institute, Messeweg 11-12, Braunschweig 38104, Germany
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Yokota SC, Broeckling C, H S Seshadri A. Pollen foraging preferences in honey bees and the nutrient profiles of the pollen. Sci Rep 2024; 14:15028. [PMID: 38951538 PMCID: PMC11217361 DOI: 10.1038/s41598-024-65569-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 06/21/2024] [Indexed: 07/03/2024] Open
Abstract
Honey bees are important insect pollinators that provide critical pollination services to fruit and nut crops in the US. They face challenges likely due to pressures associated with agricultural intensification related habitat loss. To better understand this, pollen preferences of foraging bees and the nutritional profile of pollen brought into hives by foraging bees in crop fields and nut orchards can provide valuable information. We trained bees to forage on bee-collected pollen from hives placed for pollination services in almond orchards, sunflower fields, or mixed species from inter-row plantings. Using bees trained to a certain kind of hive pollen, we applied a binary scoring system, to test preferences of these preconditioned foragers. We also performed metabolomic analyses of the hive pollen used for training and testing to elucidate their nutritional content. Irrespective of preconditioning, bees collected all the available choice pollen types, predominantly choosing hive-collected mixed species pollen (MSP), followed by almond orchard pollen. The hive-collected MSP was chemically diverse, richest in cholesterol, vitamins, and phytochemicals quercetin, kaempferol, coumarin, and quinine, but was not consistently high for essential amino acids and polyunsaturated fatty acids. Although diversity in chemical profiles may not directly relate to plant species diversity, our results suggest that foragers collect a variety of pollen types when available reiterating the importance of diverse floral resources.
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Affiliation(s)
- Seiji C Yokota
- Invasive Species and Pollinator Health Research Unit, USDA-ARS/PWA/WRRC, Davis, CA, 95616, USA
| | - Corey Broeckling
- Analytical Resources Core/Data Science Research Institute/Department of Agricultural Biology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Arathi H S Seshadri
- Pollinator Health in Southern Crops Ecosystems Research Unit, USDA-ARS/SEA, Stoneville, MS, 38776, USA.
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Liao LH, Wu WY, Berenbaum MR. Variation in Pesticide Toxicity in the Western Honey Bee (Apis mellifera) Associated with Consuming Phytochemically Different Monofloral Honeys. J Chem Ecol 2024:10.1007/s10886-024-01495-w. [PMID: 38760625 DOI: 10.1007/s10886-024-01495-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/05/2024] [Accepted: 04/12/2024] [Indexed: 05/19/2024]
Abstract
Insecticide toxicity to insect herbivores has long been known to vary across different host plants; this phenomenon has been widely documented in both foliage-feeders and sap-feeders. Species-specific phytochemical content of hostplant tissues is assumed to determine the pattern of induction of insect enzymes that detoxify insecticides, but specific phytochemicals have rarely been linked to host plant-associated variation in pesticide toxicity. Moreover, no studies to date have examined the effects of nectar source identity and phytochemical composition on the toxicity of insecticides to pollinators. In this study, we compared LD50 values for the insecticide bifenthrin, a frequent contaminant of nectar and pollen in agroecosystems, in the western honey bee, Apis mellifera, consuming three phytochemically different monofloral honeys: Nyssa ogeche (tupelo), Robinia pseudoacacia (black locust), and Fagopyrum esculentum (buckwheat). We found that bifenthrin toxicity (LD50) values for honey bees across different honey diets is linked to their species-specific phytochemical content. The profiles of phenolic acids and flavonoids of buckwheat and locust honeys are richer than is the profile of tupelo honey, with buckwheat honey containing the highest total content of phytochemicals and associated with the highest bifenthrin LD50 in honey bees. The vector fitting in the ordination analysis revealed positive correlations between LD50 values and two honey phytochemical richness estimates, Chao1 and Abundance-based Coverage Estimator (ACE). These findings suggest unequal effects among different phytochemicals, consistent with the interpretation that certain compounds, including ones that are rare, may have a more pronounced effect in mitigating pesticide toxicity.
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Affiliation(s)
- Ling-Hsiu Liao
- Department of Entomology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
| | - Wen-Yen Wu
- Department of Entomology, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - May R Berenbaum
- Department of Entomology, University of Illinois Urbana-Champaign, Urbana, IL, USA
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Zhang G, Dilday S, Kuesel RW, Hopkins B. Phytochemicals, Probiotics, Recombinant Proteins: Enzymatic Remedies to Pesticide Poisonings in Bees. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:54-62. [PMID: 38127782 PMCID: PMC10785755 DOI: 10.1021/acs.est.3c07581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/30/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023]
Abstract
The ongoing global decline of bees threatens biodiversity and food safety as both wild plants and crops rely on bee pollination to produce viable progeny or high-quality products in high yields. Pesticide exposure is a major driving force for the decline, yet pesticide use remains unreconciled with bee conservation since studies demonstrate that bees continue to be heavily exposed to and threatened by pesticides in crops and natural habitats. Pharmaceutical methods, including the administration of phytochemicals, probiotics (beneficial bacteria), and recombinant proteins (enzymes) with detoxification functions, show promise as potential solutions to mitigate pesticide poisonings. We discuss how these new methods can be appropriately developed and applied in agriculture from bee biology and ecotoxicology perspectives. As countless phytochemicals, probiotics, and recombinant proteins exist, this Perspective will provide suggestive guidance to accelerate the development of new techniques by directing research and resources toward promising candidates. Furthermore, we discuss practical limitations of the new methods mentioned above in realistic field applications and propose recommendations to overcome these limitations. This Perspective builds a framework to allow researchers to use new detoxification techniques more efficiently in order to mitigate the harmful impacts of pesticides on bees.
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Affiliation(s)
- Ge Zhang
- Department of Entomology, Washington State University, Pullman, Washington 99164, United States
| | - Sam Dilday
- Department of Entomology, Washington State University, Pullman, Washington 99164, United States
| | - Ryan William Kuesel
- Department of Entomology, Washington State University, Pullman, Washington 99164, United States
| | - Brandon Hopkins
- Department of Entomology, Washington State University, Pullman, Washington 99164, United States
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Erban T, Parizkova K, Sopko B, Talacko P, Markovic M, Jarosova J, Votypka J. Imidacloprid increases the prevalence of the intestinal parasite Lotmaria passim in honey bee workers. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 905:166973. [PMID: 37699488 DOI: 10.1016/j.scitotenv.2023.166973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 09/05/2023] [Accepted: 09/08/2023] [Indexed: 09/14/2023]
Abstract
A challenge in bee protection is to assess the risks of pesticide-pathogen interactions. Lotmaria passim, a ubiquitous unicellular parasite in honey bees, is considered harmful under specific conditions. Imidacloprid causes unpredictable side effects. Research indicates that both L. passim and imidacloprid may affect the physiology, behavior, immunity, microbiome and lifespan of honey bees. We designed cage experiments to test whether the infection of L. passim is affected by a sublethal dose of imidacloprid. Workers collected at the time of emergence were exposed to L. passim and 2.5 μg/L imidacloprid in the coexposure treatment group. First, samples of bees were taken from cages since they were 5 days old and 3 days postinfection, i.e., after finishing an artificial 24 h L. passim infection. Additional bees were collected every two additional days. In addition, bees frozen at the time of emergence and collected from the unexposed group were analyzed. Abdomens were analyzed using qPCR to determine parasite load, while corresponding selected heads were subjected to a label-free proteomic analysis. Our results show that bees are free of L. passim at the time of emergence. Furthermore, imidacloprid considerably increased the prevalence as well as parasite loads in individual bees. This means that imidacloprid facilitates infection, enabling faster parasite spread in a colony and potentially to surrounding colonies. The proteomic analysis of bee heads showed that imidacloprid neutralized the increased transferrin 1 expression by L. passim. Importantly, this promising marker has been previously observed to be upregulated by infections, including gut parasites. This study contributes to understanding the side effects of imidacloprid and demonstrates that a single xenobiotic/pesticide compound can interact with the gut parasite. Our methodology can be used to assess the effects of different compounds on L. passim.
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Affiliation(s)
- Tomas Erban
- Proteomics and Metabolomics Laboratory, Crop Research Institute, Drnovska 507/73, Prague 6-Ruzyne CZ-161 06, Czechia.
| | - Kamila Parizkova
- Department of Parasitology, Faculty of Science, Charles University, Vinicna 1594/7, Prague 2 CZ-128 00, Czechia
| | - Bruno Sopko
- Proteomics and Metabolomics Laboratory, Crop Research Institute, Drnovska 507/73, Prague 6-Ruzyne CZ-161 06, Czechia
| | - Pavel Talacko
- Proteomics Core Facility, Faculty of Science, BIOCEV, Charles University, Prumyslova 595, Vestec CZ-252 50, Czechia
| | - Martin Markovic
- Proteomics and Metabolomics Laboratory, Crop Research Institute, Drnovska 507/73, Prague 6-Ruzyne CZ-161 06, Czechia
| | - Jana Jarosova
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague 6-Lysolaje CZ-165 02, Czechia
| | - Jan Votypka
- Department of Parasitology, Faculty of Science, Charles University, Vinicna 1594/7, Prague 2 CZ-128 00, Czechia; Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branisovska 1160/31, Ceske Budejovice CZ-37005, Czechia
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Bernklau E, Arathi HS. Seasonal patterns of beneficial phytochemical availability in honey and stored pollen from honey bee colonies in large apiaries. JOURNAL OF ECONOMIC ENTOMOLOGY 2023; 116:1069-1077. [PMID: 37247384 DOI: 10.1093/jee/toad096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 04/24/2023] [Accepted: 05/10/2023] [Indexed: 05/31/2023]
Abstract
Honey bees (Apis mellifera L.; Hymenoptera, Apidae) are the most efficient pollinators in agroecosystems, responsible for the successful production of fruits, nuts, and vegetables, but they continue to face debilitating challenges. One of the major factors leading to these challenges could be linked to poor nutrition that results in weakening the colony, increasing susceptibility to pests and pathogens, and reducing the ability of bees to adapt to other abiotic stresses. Extensively used for commercial pollination, honey bee colonies regularly face exposure to limited diversity in their pollen diet as they are placed in flowering monocrops. Lack of access to diverse plant species compromises the availability of plant secondary compounds (phytochemicals), which, in small amounts, provide significant benefits to honey bee health. We analyzed the beneficial phytochemical content of honey and stored pollen (bee bread) samples from colonies in large apiaries through the active bee season. Samples were evaluated for 4 beneficial phytochemicals (caffeine, kaempferol, gallic acid, and p-coumaric acid), which have previously been shown to improve honey bee health. Our results, as relevant to the apiary locations in the study, indicated that p-coumaric acid is uniformly available throughout the season. Caffeine is completely absent, and gallic acid and kaempferol are not regularly available. Our results suggest the need to explore the potential to deliver beneficial phytochemicals as nutritional supplements to improve bee health. It may be vital for the pollination industry to consider such targeted dietary supplementation as beekeepers strive to meet the increasing demand for crop pollination services.
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Affiliation(s)
- Elisa Bernklau
- Department of Agricultural Biology, Colorado State University, Fort Collins, CO 80525, USA
| | - H S Arathi
- Invasive Species and Pollinator Health Research Unit, USDA-ARS, Davis, CA 95616, USA
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Motta EVS, Arnott RLW, Moran NA. Caffeine Consumption Helps Honey Bees Fight a Bacterial Pathogen. Microbiol Spectr 2023; 11:e0052023. [PMID: 37212661 PMCID: PMC10269917 DOI: 10.1128/spectrum.00520-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 05/07/2023] [Indexed: 05/23/2023] Open
Abstract
Caffeine has long been used as a stimulant by humans. Although this secondary metabolite is produced by some plants as a mechanism of defense against herbivores, beneficial or detrimental effects of such consumption are usually associated with dose. The Western honey bee, Apis mellifera, can also be exposed to caffeine when foraging at Coffea and Citrus plants, and low doses as are found in the nectar of these plants seem to boost memory learning and ameliorate parasite infection in bees. In this study, we investigated the effects of caffeine consumption on the gut microbiota of honey bees and on susceptibility to bacterial infection. We performed in vivo experiments in which honey bees, deprived of or colonized with their native microbiota, were exposed to nectar-relevant concentrations of caffeine for a week, then challenged with the bacterial pathogen Serratia marcescens. We found that caffeine consumption did not impact the gut microbiota or survival rates of honey bees. Moreover, microbiota-colonized bees exposed to caffeine were more resistant to infection and exhibited increased survival rates compared to microbiota-colonized or microbiota-deprived bees only exposed to the pathogen. Our findings point to an additional benefit of caffeine consumption in honey bee health by protecting against bacterial infections. IMPORTANCE The consumption of caffeine is a remarkable feature of the human diet. Common drinks, such as coffee and tea, contain caffeine as a stimulant. Interestingly, honey bees also seem to like caffeine. They are usually attracted to the low concentrations of caffeine found in nectar and pollen of Coffea plants, and consumption improves learning and memory retention, as well as protects against viruses and fungal parasites. In this study, we expanded these findings by demonstrating that caffeine can improve survival rates of honey bees infected with Serratia marcescens, a bacterial pathogen known to cause sepsis in animals. However, this beneficial effect was only observed when bees were colonized with their native gut microbiota, and caffeine seemed not to directly affect the gut microbiota or survival rates of bees. Our findings suggest a potential synergism between caffeine and gut microbial communities in protection against bacterial pathogens.
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Affiliation(s)
- Erick V. S. Motta
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA
| | - Ryan L. W. Arnott
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA
| | - Nancy A. Moran
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, USA
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Patouna A, Vardakas P, Skaperda Z, Spandidos DA, Kouretas D. Evaluation of the antioxidant potency of Greek honey from the Taygetos and Pindos mountains using a combination of cellular and molecular methods. Mol Med Rep 2023; 27:54. [PMID: 36660937 PMCID: PMC9879079 DOI: 10.3892/mmr.2023.12941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 01/05/2023] [Indexed: 01/19/2023] Open
Abstract
Honey is a complex mixture, containing ~180 compounds, produced by the Apis melifera bees, with promising antimicrobial and antioxidant properties. Nevertheless, the mechanisms through which honey exerts its effects remain under investigation. Plant antioxidants are found in honey and other bee products exhibiting a high bioactivity and molecular diversity. The aim of the present study was to estimate the antioxidant capacity of honey collected from areas in Greece by small‑scale producers by i) using in vitro cell free assays; and ii) by investigating the effects of honey varieties on the redox status of a liver cancer cell line (HepG2) using non‑cytotoxic concentrations. The findings of the present study will allow for the identification of Greek honeys with promising antioxidant capacity. For this purpose, six types of honey with various floral origins were examined in cell‑free assays followed by cell‑based techniques using flow cytometric analysis and redox biomarker level determination in order to evaluate the potential alterations in the intracellular redox system. The results indicated various mechanisms of action that are dependent on the honey type, concentration dependency and high antioxidant capacity. The extended findings from the literature confirm the ability of raw honey to influence the redox status of HepG2 cells. Nevertheless additional investigations are required to elucidate their mechanisms of action in cell line models.
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Affiliation(s)
- Anastasia Patouna
- Department of Biochemistry and Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Periklis Vardakas
- Department of Biochemistry and Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Zoi Skaperda
- Department of Biochemistry and Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Demetrios A. Spandidos
- Laboratory of Clinical Virology, Medical School, University of Crete, 71003 Heraklion, Greece
| | - Demetrios Kouretas
- Department of Biochemistry and Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece,Correspondence to: Professor Demetrios Kouretas, Department of Biochemistry and Biotechnology, School of Health Sciences, University of Thessaly, Viopolis, Mezourlo, 41500 Larissa, Greece, E-mail:
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Niño EL, Yokota S, Stacy WH, Arathi H. Dietary phytochemicals alter hypopharyngeal gland size in honey bee (Apis mellifera L.) workers. Heliyon 2022; 8:e10452. [PMID: 36097486 PMCID: PMC9463586 DOI: 10.1016/j.heliyon.2022.e10452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/19/2022] [Accepted: 08/22/2022] [Indexed: 11/16/2022] Open
Abstract
Honey bees are the most efficient pollinators of several important fruits, nuts and vegetables and are indispensable for the profitable production of these crops. Health and performance of honey bee colonies have been declining for decades due to a combination of factors including poor nutrition, agrochemicals, pests and diseases. Bees depend on a diversity of plants for nutrition as pollen is the predominant protein and lipid source, and nectar, the source of carbohydrates for larval development. Additionally, pollen and nectar also contain small amounts of plant secondary metabolites or phytochemicals that are primarily plant defense compounds. Bees have coevolved to benefit from these compounds as seen by the improved longevity, pathogen tolerance and gut microbiome abundance in worker bees whose diets were supplemented with select phytochemicals. Here we investigate the impact of four phytochemicals, known to benefit bees, – caffeine, kaempferol, gallic acid and p-coumaric acid, on hypopharyngeal gland (HPG) size of nurse bees. Newly emerged bees were provided with 25 ppm of each of the four phytochemicals in 20% (w/v) sucrose solution and the size of HPGs were measured after a 10 d period. Bees that received p-coumaric acid or kaempferol showed a significant increase in HPG size. A significant decrease in HPG size was seen in bees receiving caffeine or gallic acid. The implication of our findings on worker bee ontogeny, transitioning from nurses to foragers and relevance to foraging related competencies are discussed. It is critical that bees have access to phytochemicals to ensure colony health and performance. Such access could be through natural habitats that provide a diversity of pollen and nectar sources or through dietary supplements for bee colonies.
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