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Division of labor is a striking feature observed in honey bees and many other social insects. Division of labor has been claimed to benefit fitness. In honey bees, the adult work force may be viewed as divided between non-foraging hive bees that rear brood and maintain the nest, and foragers that collect food outside the nest. Honey bee brood pheromone is a larval pheromone that serves as an excellent empirical tool to manipulate foraging behaviors and thus division of labor in the honey bee. Here we use two different doses of brood pheromone to alter the foraging stimulus environment, thus changing demographics of colony division of labor, to demonstrate how division of labor associated with brood rearing affects colony growth rate. We examine the effects of these different doses of brood pheromone on individual foraging ontogeny and specialization, colony level foraging behavior, and individual glandular protein synthesis. Low brood pheromone treatment colonies exhibited significantly higher foraging population, decreased age of first foraging and greater foraging effort, resulting in greater colony growth compared to other treatments. This study demonstrates how division of labor associated with brood rearing affects honey bee colony growth rate, a token of fitness. [ABSTRACT FROM AUTHOR]

Abstract: Insecticidal properties of protease inhibitors have been established in transgenic plants. In the wake of continuous research and rapid development of protease inhibitors it is important to assess possible effects on beneficial insects like the honey bee (Apis mellifera L.). In this study, newly emerged caged bees were fed pollen diets containing three different concentrations (0.1%, 0.5% and 1% w:w) of soybean trypsin inhibitor (SBTI). Hypopharyngeal gland protein content, total midgut proteolytic enzyme activity of these bees, and survival were measured. Bees fed 1% SBTI had significantly reduced hypopharyngeal gland protein content and midgut proteolytic enzyme activity. There were no significant differences between control, 0.1% and 0.5% SBTI treatments. Bees fed a diet containing 1% SBTI had the lowest survival, followed by 0.5% and 0.1%, over a 30-day period. We concluded that nurse bees fed a pollen diet containing at least 1% SBTI would be poor producers of larval food, potentially threatening colony growth and maintenance. [Copyright &y& Elsevier]

Simple Summary: Phytosterols are important micronutrients that are essential for production of insect molting hormones and cellular membrane integrity. Past research has shown that the key phytosterol that honey bees need is 24-methylenecholesterol. This phytosterol improves honey bee longevity and sustains brood production. Hence, it is important to understand how 24-methylenecholesterol can shape honey bee physiology by altering protein profiles of vital honey bee tissues. Nurse bees secrete glandular secretions (brood food) using hypopharyngeal and mandibular glands in their head regions. Further, it has been shown that this sterol is selectively accumulated in nurse bee heads. Thus, it is imperative to examine the protein profiles of nurse bee heads, in response to dietary 24-methylenecholesterol manipulation. In this study, groups of newly emerged nurse bees were fed with varying concentrations of dietary 24-methylenecholesterol, while the control groups received no sterol. We found that dietary sterol manipulation altered the protein profiles in nurse bee heads, with important nutritional marker proteins being upregulated in high dietary sterol groups. The important proteins identified in this study may serve as vital markers of nutritional stress related to sterols in honey bees, paving the way for future research on bee nutrition. Phytosterols are important micronutrients that are precursors of important molting hormones and help maintain cellular membrane integrity in insects including bees. Previous research has shown that 24-methylenecholesterol is a key phytosterol that enhances honey bee longevity and improves nurse bee physiology. Nurse bees have the ability to selectively transfer this sterol to developing larvae through brood food. This study examines the physiological impacts of 24-methylenecholesterol on nurse bees, by analyzing the protein profiles of nurse bee heads upon dietary sterol manipulation. Dietary experimental groups consisting of newly emerged honey bees were provided with varying concentrations of 24-methylenecholesterol for three weeks. At the end of the study, honey bees were collected and proteomic analysis was performed on honey bee heads. A total of 1715 proteins were identified across experimental groups. The mean relative abundances of nutritional marker proteins (viz. major royal jelly proteins 1, 4, 5, 7) were higher in experimental groups supplemented with higher dietary sterol concentrations, when compared with the control dietary group. The mean relative abundances of important enzymatic proteins (aminopeptidase and calcium-transporting ATPase) were higher in control groups, whereas mean relative abundances of oxysterol-binding protein and fatty acid-binding protein were higher in higher dietary sterol groups. [ABSTRACT FROM AUTHOR]

Honey bee larvae are dependent on the social structure of colony for their provisioning and survival. With thousands of larvae being managed collectively by groups of foragers (collecting food resources) and nurse bees (processing food and provisioning larvae), coordination of colony efforts in rearing brood depends on multiple dynamic cues of larval presence and needs. Much of these cues appear to be chemical, with larvae producing multiple pheromones, major being brood ester pheromone (BEP; nonvolatile blend of fatty acid esters) that elicits both short-term releaser effects and long-term primer effects. While BEP can affect colony food collection and processing with the signaling of larval presence, it is unclear if BEP signals individual larval needs. To understand this aspect, in a series of experiments we manipulated larval feeding environment by depriving larvae from adult bee contact for 4-h period and examined (1) nurse bee interactions with contact-deprived and nondeprived larvae and larval extracts; (2) forager bee responses to contact-deprived and nondeprived larval extracts. We also characterized BEP of contact-deprived and nondeprived larvae. We found that nurse honey bees tend to aggregate more over contact-deprived larvae when compared with nondeprived larvae, but that these effects were not found in response to whole hexane extracts. Our analytical results suggest that BEP components changed in both quantity and quality over short period of contact deprivation. These changes affected foraging behavior, but did not appear to directly affect nursing behavior, suggesting that different chemical cues are involved in regulating nursing effort to individual larvae. [ABSTRACT FROM AUTHOR]

Although poor nutrition is cited as one of the crucial factors in global pollinator decline, the requirements and role of several important nutrients (especially micronutrients) in honey bees are not well understood. Micronutrients, viz. phytosterols, play a physiologically vital role in insects as precursors of important molting hormones and building blocks of cellular membranes. There is a gap in comprehensive understanding of the impacts of dietary sterols on honey bee physiology. In the present study, we investigated the role of 24-methylenecholesterol—a key phytosterol—in honey bee nutritional physiology. Artificial diets with varying concentrations of 24-methylenecholesterol (0%, 0.1%. 0.25%, 0.5%, 0.75%, and 1% dry diet weight) were formulated and fed to honey bees in a laboratory cage experiment. Survival, diet consumption, head protein content, and abdominal lipid contents were significantly higher in dietary sterol-supplemented bees. Our findings provide additional insights regarding the role of this important sterol in honey bee nutritional physiology. The insights gleaned from this study could also advance the understanding of sterol metabolism and regulation in other bee species that are dependent on pollen for sterols, and assist in formulation of a more complete artificial diet for honey bees (Apis mellifera Linnaeus, 1758) (Hymenoptera: Apidae). [ABSTRACT FROM AUTHOR]

Honey bees provision glandular secretions in the form of royal jelly as larval nourishment to developing queens. Exposure to chemicals and nutritional conditions can influence queen development and thus impact colony fitness. Previous research reports that royal jelly remains pesticide-free during colony-level exposure and that chemical residues are buffered by the nurse bees. However, the impacts of pesticides can also manifest in quality and quantity of royal jelly produced by nurse bees. Here, we tested how colony exposure to a multi-pesticide pollen treatment influences the amount of royal jelly provisioned per queen and the additional impacts on royal jelly nutritional quality. We observed differences in the metabolome, proteome, and phytosterol compositions of royal jelly synthesized by nurse bees from multi-pesticide exposed colonies, including significant reductions of key nutrients such as 24-methylenecholesterol, major royal jelly proteins, and 10-hydroxy-2-decenoic acid. Additionally, quantity of royal jelly provisioned per queen was lower in colonies exposed to pesticides, but this effect was colony-dependent. Pesticide treatment had a greater impact on royal jelly nutritional composition than the weight of royal jelly provisioned per queen cell. These novel findings highlight the indirect effects of pesticide exposure on queen developmental nutrition and allude to social consequences of nurse bee glandular degeneration. Image 1 • Multi-pesticide oral exposure can alter royal jelly production. • Exposed colonies produced royal jelly with lower concentrations of phytosterols. • Abundances of metabolites and proteins were different between treatments. • Amount of royal jelly provisioned per queen larva was not significantly different. [ABSTRACT FROM AUTHOR]

Poor nutrition is an important factor in global bee population declines. A significant gap in knowledge persists regarding the role of various nutrients (especially micronutrients) in honey bees. Sterols are essential micronutrients in insect diets and play a physiologically vital role as precursors of important molting hormones and building blocks of cellular membranes. Sterol requirements and metabolism in honey bees are poorly understood. Among all pollen sterols, 24-methylenecholesterol is considered the key phytosterol required by honey bees. Nurse bees assimilate this sterol from dietary sources and store it in their tissues as endogenous sterol, to be transferred to the growing larvae through brood food. This study examined the duration of replacement of such endogenous sterols in honey bees. The dietary 13C-labeled isotopomer of 24-methylenecholesterol added to artificial bee diet showed differential, progressive in vivo assimilation across various honey bee tissues. Significantly higher survival, diet consumption, head protein content and abdominal lipid content were observed in the dietary sterol-supplemented group than in the control group. These findings provide novel insights into phytosterol utilization and temporal pattern of endogenous 24-methylenecholesterol replacement in honey bees. [ABSTRACT FROM AUTHOR]

Honey bee colony losses in the US have exceeded acceptable levels for at least a decade, leaving beekeepers in need of management practices to improve colony health and survival. Here, an empirical Best Management Practice (BMP) regimen was tested, comprised of the top four management practices associated with reduced colony mortality in backyard beekeeping operations according to Bee Informed Partnership Loss and Management survey results. Seven study locations were established across the US, and each location consisted of ten colonies treated according to empirical BMPs and ten according to average beekeeping practice. After 3 years, colonies treated according to empirical BMPs experienced reduced Varroa infestation, viral infection, and mortality compared to colonies managed with Average practices. In addition, BMP colonies produced more new colonies via splits. The colonies under Average practices were given chemical Varroa treatments only once per year, and thus spent more months above economic threshold of 3.0 mites/100 bees. Increased time spent above the economic threshold was significantly correlated to both increased viral infection and colony mortality. This study demonstrates the cumulative effects of management and colony health stressors over months and years, especially the dire importance of regular Varroa monitoring and management. [ABSTRACT FROM AUTHOR]

Pesticide exposures can have detrimental impacts on bee pollinators, ranging from immediate mortality to sub-lethal impacts. Flupyradifurone is the active ingredient in Sivanto™ and sulfoxaflor is the active ingredient in Transform®. They are both relatively new insecticides developed with an intent to reduce negative effects on bees, when applied to bee-attractive crops. With the growing concern regarding pollinator health and pollinator declines, it is important to have a better understanding of any potential negative impacts, especially sub-lethal, of these pesticides on bees. This study reports novel findings regarding physiological stress experienced by bees exposed to field application rates of these two insecticides via a Potter Tower sprayer. Two contact exposure experiments were conducted—a shorter 6-hour study and a longer 10-day study. Honey bee mortality, sugar syrup and water consumption, and physiological responses (oxidative stress and apoptotic protein assays) were assessed in bees exposed to Sivanto™ and Transform®, and compared to bees in control group. For the longer, 10-day contact exposure experiment, only the Sivanto™ group was compared to the control group, as high mortality recorded in the sulfoxaflor treatment group during the shorter contact exposure experiment, made the latter group unfeasible to test in the longer 10-days experiment. In both the studies, sugar syrup and water consumptions were significantly different between treatment groups and controls. The highest mortality was observed in Transform® exposed bees, followed by the Sivanto™ exposed bees. Estimates of reactive oxygen/nitrogen species indicated significantly elevated oxidative stress in both pesticide treatment groups, when compared to controls. Caspase-3 protein assays, an indicator of onset of apoptosis, was also significantly higher in the pesticide treatment groups. These differences were largely driven by post exposure duration, indicating sub-lethal impacts. Further, our findings also emphasize the need to revisit contact exposure impacts of Sivanto™, given the sub-lethal impacts and mortality observed in our long-term (10-day) contact exposure experiment. [ABSTRACT FROM AUTHOR]

Nosema ceranae is a widely prevalent microsporidian parasite in the western honey bee. There is considerable uncertainty regarding infection dynamics of this important pathogen in honey bee colonies. Understanding the infection dynamics at the colony level may aid in development of a reliable sampling protocol for N. ceranae diagnosis, and provide insights into efficient treatment strategies. The primary objective of this study was to characterize the prevalence (proportion of the sampled bees found infected) and intensity (number of spores per bee) of N. ceranae infection in bees from various age cohorts in a colony. We examined N. ceranae infection in both overwintered colonies that were naturally infected with N. ceranae and in quadruple cohort nucleus colonies that were established and artificially inoculated with N. ceranae. We also examined and quantified effects of N. ceranae infection on hypopharyngeal gland protein content and gut pH. There was no correlation between the prevalence and intensity of N. ceranae infection in composite samples (pooled bee samples used for analysis). Our results indicated that the prevalence and intensity of N. ceranae infection is significantly influenced by honey bee age. The N. ceranae infection prevalence values from composite samples of background bees (unmarked bees collected from four different locations in a colony) were not significantly different from those pertaining to marked-bee age cohorts specific to each sampling date. The foraging-aged bees had a higher prevalence of N. ceranae infection when compared to nurse-aged bees. N. ceranae did not have a significant effect on hypopharyngeal gland protein content. Further, there was no significant difference in mean gut pH of N. ceranae infected bees and non-infected bees. This study provides comprehensive insights into N. ceranae infection dynamics at the colony level, and also demonstrates the effects of N. ceranae infection on hypopharyngeal gland protein content and midgut pH. [ABSTRACT FROM AUTHOR]

Multiple stressors are currently threatening honey bee health, including pests and pathogens. Among honey bee pathogens, Nosema ceranae is a microsporidian found parasitizing the western honey bee ( Apis mellifera ) relatively recently. Honey bee colonies are fed pollen or protein substitute during pollen dearth to boost colony growth and immunity against pests and pathogens. Here we hypothesize that N. ceranae intensity and prevalence will be low in bees receiving high pollen diets, and that honey bees on high pollen diets will have higher survival and/or increased longevity. To test this hypothesis we examined the effects of different quantities of pollen on (a) the intensity and prevalence of N. ceranae and (b) longevity and nutritional physiology of bees inoculated with N. ceranae . Significantly higher spore intensities were observed in treatments that received higher pollen quantities (1:0 and 1:1 pollen:cellulose) when compared to treatments that received relatively lower pollen quantities. There were no significant differences in N. ceranae prevalence among different pollen diet treatments. Interestingly, the bees in higher pollen quantity treatments also had significantly higher survival despite higher intensities of N. ceranae . Significantly higher hypopharyngeal gland protein was observed in the control (no Nosema infection, and receiving a diet of 1:0 pollen:cellulose), followed by 1:0 pollen:cellulose treatment that was inoculated with N. ceranae . Here we demonstrate that diet with higher pollen quantity increases N. ceranae intensity, but also enhances the survival or longevity of honey bees. The information from this study could potentially help beekeepers formulate appropriate protein feeding regimens for their colonies to mitigate N. ceranae problems. [ABSTRACT FROM AUTHOR]

The decline in populations of insect pollinators is a global concern. While multiple factors are implicated, there is uncertainty surrounding the contribution of certain groups of pesticides to losses in wild and managed bees. Nanotechnology-based pesticides (NBPs) are formulations based on multiple particle sizes and types. By packaging active ingredients in engineered particles, NBPs offer many benefits and novel functions, but may also exhibit different properties in the environment when compared with older pesticide formulations. These new properties raise questions about the environmental disposition and fate of NBPs and their exposure to pollinators. Pollinators such as honey bees have evolved structural adaptations to collect pollen, but also inadvertently gather other types of environmental particles which may accumulate in hive materials. Knowledge of the interaction between pollinators, NBPs, and other types of particles is needed to better understand their exposure to pesticides, and essential for characterizing risk from diverse environmental contaminants. The present review discusses the properties, benefits and types of nanotechnology-based pesticides, the propensity of bees to collect such particles and potential impacts on bee pollinators. [ABSTRACT FROM AUTHOR]

Background: Significant annual honey bee colony losses have been reported in the USA and across the world over the past years. Malnutrition is one among several causative factors for such declines. Optimal nutrition serves as the first line of defense against multiple stressors such as parasites/pathogens and pesticides. Given the importance of nutrition, it is imperative to understand bee nutrition holistically, identifying dietary sources that may fulfill bee nutritional needs. Pollen is the primary source of protein for bees and is critical for brood rearing and colony growth. Currently, there is significant gap in knowledge regarding the chemical and nutritional composition of pollen. Methods: Targeted sterol analysis and untargeted metabolomics were conducted on five commercially available crop pollens, three bee-collected crop pollens, three vegetable oils (often added to artificial protein supplements by beekeepers), and one commonly used artificial protein supplement. Results: This study reports key phytosterols and metabolites present across a spectrum of bee diets, including some of the major bee-pollinated crop pollens in the western United States. Significant differences were observed in sterol concentrations among the dietary sources tested. Among all quantified sterols, the highest concentrations were observed for 24-methylenecholesterol and further, pollen samples exhibited the highest 24-methylenecholesterol among all diet sources that were tested. Also, 236 metabolites were identified across all dietary sources examined. Conclusion: Information gleaned from this study is crucial in understanding the nutritional landscape available to all bee pollinators and may further assist in future efforts to develop comprehensive database of nutrients and metabolites present in all bee diets. [ABSTRACT FROM AUTHOR]