Monofloral Pollen Research Articles

X-ray fluorescence profile of Brazilian bee pollen

Brazil is known for its high biodiversity, which leads to distinguishable properties in bee pollen composition. Besides, profiling their features as a marker of good quality would help beekeepers to market the pollen better and also understand the health status of their beehives. Herein, 40 pollen samples were assessed for ashes, pH, and an X-ray fluorescence profile, aiming to classify them through a multivariate statistical approach. Ashes were associated with higher content of K and Ca ranging from 1.77% to 4.00%, and pH is affected by floral source (3.82 – 4.94) being more comparable for mono-floral pollens. Characteristic X-rays were observed for the elements Br, Ca, Cu, Fe, K, Mn, P, Rb, S, Sr, and Zn, with a predominance of the macronutrients K and Ca. The elemental distribution featured K, Ca, P, Zn, and S in the Northeast. Mn, Rb, and Fe in the South and Cu and Sr in the Southeast. Pollen composition showed a nutrient availability pattern that reflected the regional soil characteristics in Brazil. Therefore, X-ray fluorescence is a feasible technique for assessing pollen composition as a quick and environmentally friendly alternative.

Diversity in bee pollen from three phytogeographical regions in Turkey

Bee pollen is a mixture of bee secretions, plant pollen and nectar and has a valuable nutritional composition for both bees and humans. The aim of this study was to investigate plant diversity in pollen collected by honey bees from three phytogeographic regions (Mediterranean, Euro-Siberian and Irano-Turanian). Melissopalynological analysis of bee pollen pellets collected from Mediterranean (15), Irano-Turanian (6), and Euro-Siberian (7) in Turkey were analysed. The Shannon–Weaver diversity (H′), richness, and Pielou’s evenness index (J′) were used to compare between bee pollen pellets. In all three phytogeographic regions, herbaceous species are more than tree and shrub species. A total of 80 pollen types belonging to 38 families were identified in these regions. Cistus sp., Trifolium sp., Papaver sp. and Verbascum sp. in Mediterranean; Filipendula sp. and Salix sp. in Irano-Turanian; and Sambucus sp., Helianthemum sp., Onobrychis sp., and Rubus sp. in Euro-Siberian were all determined to be predominant taxa. When pollen was evaluated based on its morphological characteristics, bees preferred medium (41), isopolar (74), prolate (38), 3-colporate (49), reticulate (23), and psilate (22) pollen than other characteristics. The H′ values in polyfloral pollen were higher than bifloral and monofloral pollens. The J’ of polyfloral, bifloral, and monofloral was 0.73 to 0.85, 0.68 to 0.84, and 0.32–0.97, respectively. The results obtained in this study, are important for the establishment of beekeeping in the right areas in terms of plant diversity.

The microbiome and gene expression of honey bee workers are affected by a diet containing pollen substitutes.

Pollen is the primary source of dietary protein for honey bees. It also includes complex polysaccharides in its outer coat, which are largely indigestible by bees but can be metabolized by bacterial species within the gut microbiota. During periods of reduced availability of floral pollen, supplemental protein sources are frequently provided to managed honey bee colonies. The crude proteins in these supplemental feeds are typically byproducts from food manufacturing processes and are rarely derived from pollen. Our experiments on the impact of different diets showed that a simplified pollen-free diet formulated to resemble the macronutrient profile of a monofloral pollen source resulted in larger microbial communities with reduced diversity, reduced evenness, and reduced levels of potentially beneficial hive-associated bacteria. Furthermore, the pollen-free diet sharply reduced the expression of genes central to honey bee development. In subsequent experiments, we showed that these shifts in gene expression may be linked to colonization by the gut microbiome. Lastly, we demonstrated that for bees inoculated with a defined gut microbiota, those raised on an artificial diet were less able to suppress infection from a bacterial pathogen than those that were fed natural pollen. Our findings demonstrate that a pollen-free diet significantly impacts the gut microbiota and gene expression of honey bees, indicating the importance of natural pollen as a primary protein source.

Characterisation of Bee Pollen from the Marche Region (Italy) According to the Botanical and Geographical Origin with Analysis of Antioxidant Activity and Colour, Using a Chemometric Approach.

Attempts have often been made to isolate and characterise monofloral pollens to correlate nutritional with botanical properties. Nevertheless, pollen harvested in a particular area that can have a high biodiversity could have healthier properties. In addition, the analysis of the pollen's botanical composition can be important for characterising the typical flora of a specific geographical area. On this basis, various pollens collected in different locations of the Marche region (Italy) and in different harvesting periods were analyzed for botanical composition and antioxidant (total phenolic content, ABTS, DPPH and ORAC tests), granulometry and colour (CIE L*a*b*) properties to evaluate the biodiversity of pollen sources within a particular geographical area and to correlate this to the nutraceutical characteristics. Antioxidant activity results showed values generally higher than those of monofloral pollens harvested in the same areas but manually separated according to colour, shape and size. This suggests that even the floral species present in low percentages may have an influence on the nutraceutical properties of these products. The multivariate statistical elaboration of the obtained results permitted the separation of samples containing a prevalent botanical species and the grouping of all the samples into separate clusters corresponding to different areas of Marche.

Young honeybees show learned preferences after experiencing adulterated pollen

Pollen selection affects honeybee colony development and productivity. Considering that pollen is consumed by young in-hive bees, and not by foragers, we hypothesized that young bees learn pollen cues and adjust their preferences to the most suitable pollens. To assess whether young bees show preferences based on learning for highly or poorly suitable pollens, we measured consumption preferences for two pure monofloral pollens after the bees had experienced one of them adulterated with a deterrent (amygdalin or quinine) or a phagostimulant (linoleic acid). Preferences were obtained from nurse-aged bees confined in cages and from nurse bees in open colonies. Furthermore, we tested the bees’ orientation in a Y-maze using a neutral odour (Linalool or Nonanal) that had been previously associated with an amygdalin-adulterated pollen. Consumption preferences of bees, both in cages and in colonies, were reduced for pollens that had been adulterated with deterrents and increased for pollens that had been supplemented with linoleic acid. In the Y-maze, individuals consistently avoided the odours that they had previously experienced paired with the deterrent-adulterated pollen. Results show that nurse-aged bees associate pollen-based or pollen-related cues with either a distasteful/malaise experience or a tasty/nutritious event, leading to memories that bias their pollen-mediated response.

Pollen Source Richness May Be a Poor Predictor of Bumblebee (Bombus terrestris) Colony Growth.

Agricultural intensification has drastically altered foraging landscapes for bees, with large-scale crop monocultures associated with floral diversity loss. Research on bumblebees and honeybees has shown individuals feeding on pollen from a low richness of floral sources can experience negative impacts on health and longevity relative to higher pollen source richness of similar protein concentrations. Florally rich landscapes are thus generally assumed to better support social bees. Yet, little is known about whether the effects of reduced pollen source richness can be mitigated by feeding on pollen with higher crude protein concentration, and importantly how variation in diet affects whole colony growth, rearing decisions and sexual production. Studying queen-right bumblebee (Bombus terrestris) colonies, we monitored colony development under a polyfloral pollen diet or a monofloral pollen diet with 1.5-1.8 times higher crude protein concentration. Over 6 weeks, we found monofloral colonies performed better for all measures, with no apparent long-term effects on colony mass or worker production, and a higher number of pupae in monofloral colonies at the end of the experiment. Unexpectedly, polyfloral colonies showed higher mortality, and little evidence of any strategy to counteract the effects of reduced protein; with fewer and lower mass workers being reared, and males showing a similar trend. Our findings (i) provide well-needed daily growth dynamics of queenright colonies under varied diets, and (ii) support the view that pollen protein content in the foraging landscape rather than floral species richness per se is likely a key driver of colony health and success.

The effect of pollen grain morphology on sugars content of bee-collected pollen: the significance of size and exine ornamentation

Sugars constitute the main component of bee-collected pollen, which may vary significantly among different pollen taxa according to their botanical origin and the surrounding vegetation. In this study, we investigated the significance of the pollen grain volume and exine sculpture on the sugars content of bee-collected pollen. We analysed the sugar content of 30 monofloral pollen pellets using high-performance liquid chromatography and we measured the volume of the pollen grains. The content of total sugars of pollen pellets was on average 421.0 g kg−1.We found that the volume of pollen grain affects the total content of sugars in bee-collected pollen in a statistically significant way and smaller size pollen grains had comparatively higher sugar values. On the contrary, we found no clear evidence regarding the significance of the exine ornamentation on sugar content. The results revealed that the presence of sugars in bee-collected pollen is a multifactorial issue as several parameters such as the volume of pollen grains, the botanical origin, the flowering season and surrounding vegetation may influence the results.

A citizen science supported study on seasonal diversity and monoflorality of pollen collected by honey bees in Austria

Austrian beekeepers participated in the “C.S.I. Pollen” study as citizen scientists and collected pollen from honey bee colonies in hive mounted traps every three weeks from April to September in 2014 and 2015 to uncover the seasonal availability of pollen sources for bees. 1622 pollen samples were collected and analysed using palynological light microscopy to the lowest taxonomic level possible. For 2014 and 2015 combined, 239 pollen types from more than 85 families were detected. ‘Various unknown’ species, Taraxacum-form and Plantago spp. were the pollen types collected by the majority of colonies (occurrence), whereas the most pollen grains collected were from Trifolium repens-form, Plantago spp. and Salix spp. (abundance). In spring, trees were found to be the most abundant pollen source, whereas in summer herbs dominated. On average, a colony collected pollen from 16.8 ± 4.7 (2014) and 15.0 ± 4.4 (2015) pollen types per sampling. Those numbers, however, vary between sampling dates and indicate a seasonal pattern. This is also supported by Simpson’s diversity index, which was on median 0.668. In both years, 50.0% of analysed pollen samples were partially (>50%) and 4.2% were highly monofloral (i.e. containing >90% of one pollen type). Prevalence of monofloral pollen samples peaked at the beginning and the end of the season, when pollen diversity was the lowest.

Characterization of Zygophyllum album L Monofloral Honey from El-Oued, Algeria

Background: Honey is generally evaluated by physicochemical analysis of its constituents. The manipulation of honey and its possible adulteration is reflected in many of its physicochemical properties. Objective: In this study, samples of Zygophyllum album L honey produced in El-Oued, Algeria, were characterized based on their melissopalynology, physicochemical and antioxidant properties, also polyphenol content. Methods: The physicochemical parameters of honey, such as density, moisture content, pH, free acidity, electrical conductivity (EC), total sugar content, color intensity, water insoluble solids content, hydroxymethylfurfural (HMF), ash, specific rotation, were measured. A number of antioxidant tests were performed to determine the antioxidant properties of Zygophyllum album L honey samples. The polyphenol in the Zygophyllum album L honey was measured by spectrometric determination based on folin-ciocalteu’s method. The identification and quantification of phenolic compounds were carried out by RP-HPLC (high-performance liquid chromatography). Results: All honey samples contained monofloral (67.83-91.89%) pollen belonging to Zygophyllum album L. The results of physicochemical parameters of analyzed honeys were: pH 4.33, moisture 17.2%, free acidity 41.96 meq/kg, electrical conductivity 0.408 mS/cm, HMF 11.89 mg/kg, Ash 0.246 (%), specific rotation -8.21. The Zygophyllum album L honey was extra white amber. The total sugar content ranged from 81.5 to 83. Honey samples contain high levels of gallic acid (252.53±15.56 mg/kg honey), chlorogenic acid (124.71±10.09 mg/kg) and low amounts of total polyphenol (467.82±46,98 mg GAE/kg). Conclusion: Physicochemical parameters (total acidity, pH, moisture, dry matter, ash, and qualitative hydroxymethylfurfural) were within the approved limits established by International Honey Commission.

Mineral content in monofloral bee pollen: investigation of the effect of the botanical and geographical origin

The object of this study was to determine bee pollen’s minerals composition and evaluate the effect of the botanical and geographical origin. The results showed that the predominant elements were K, P and Ca, comprising 42.5%, 31.2% and 15.7%, respectively, of the total mineral content. The analysis of 30 monofloral pollen species showed the effect of botanical origin, recording a large range among the species with the most characteristic being P (1362–9210 mg/kg), K (2684–11604 mg/kg) and Ca (446–4464 mg/kg). Their highest concentrations were found in Phacelia tanacetifolia, Erica manipuliflora and Actinidia chinensis, respectively. Furthermore, to determine the effect of geographical origin (soil, climate), monofloral pollen samples of Sinapis arvensis and Cistus creticus collected from different regions were analysed. The highest ranges were observed in composition of S. arvensis and C. creticus pollen in K and Ca. The findings of this study prove that bee pollen is a notable source of minerals, facilitating the trade of the product promoting it as a beneficial natural food supplement.

Antimicrobial activity of different monofloral bee pollens against foodborne pathogens

Antimicrobial activity of different monofloral bee pollens against foodborne pathogens

Does the Pollen Diet Influence the Production and Expression of Antimicrobial Peptides in Individual Honey Bees?

We investigated the importance of protein nutrition for honey bee immunity. Different protein diets (monofloral pollen of Helianthus spp., Sinapis spp., Asparagus spp., Castanea spp., a mixture of the four different pollen and the pollen substitute FeedbeeTM) were fed to honey bees in cages ad libitum. After 18 days of feeding, apidaecin 1 isoforms concentration in the thorax were measured using nanoflow liquid chromatography coupled with mass spectrometry. Expression levels of genes, coding for apidaecins and abaecin in the abdomen were determined using quantitative PCR. The results indicate that protein-containing nutrition in adult worker honey bees can trigger certain metabolic responses. Bees without dietary protein showed lower apidaecin 1 isoforms concentrations. The significantly lowest concentration of apidaecin 1 isoforms was found in the group that was fed no pollen diet when compared to Asparagus, Castanea, Helianthus, and Sinapis pollen or the pollen supplement FeedBeeTM. Expression levels of the respective genes were also affected by the protein diets and different expression levels of these two antimicrobial peptides were found. Positive correlation between concentration and gene expression of apidaecins was found. The significance of feeding bees with different protein diets, as well as the importance of pollen nutrition for honey bee immunity is demonstrated.

Effects of neonicotinoid insecticide exposure and monofloral diet on nest-founding bumblebee queens.

Bumblebees are among the world's most important groups of pollinating insects in natural and agricultural ecosystems. Each spring, queen bumblebees emerge from overwintering and initiate new nests, which ultimately give rise to workers and new reproductives later in the season. Nest initiation and survival are thus key drivers of both bumblebee pollination services and population dynamics. We performed the first laboratory experiment with the model bumblebee species Bombus impatiens that explores how early nesting success is impacted by the effects of temporary or more sustained exposure to sublethal levels of a neonicotinoid-type insecticide (imidacloprid at 5 ppb in nectar) and by reliance on a monofloral pollen diet, two factors that have been previously implicated in bumblebee decline. We found that queens exhibited increased mortality and dramatically reduced activity levels when exposed to imidacloprid, as well as delayed nest initiation and lower brood numbers in the nest, but partially recovered from these effects when they only received early, temporary exposure. The effects of pollen diet on individual queen- and colony-level responses were overshadowed by effects of the insecticide, although a monofloral pollen diet alone was sufficient to negatively impact brood production. These findings speak to the sensitivity of queen bumblebees during the nest initiation phase of the colony cycle, with implications for how queens and their young nests are uniquely impacted by exposure to threats such as pesticide exposure and foraging habitat unsuitability.

Physicochemical composition and antioxidant potential of bee pollen from different botanical sources in Alagoas, Brazil

ABSTRACT Bee pollen results from the mixture of pollen and floral nectar with the salivary substances of bees and has increasingly been used as a food with therapeutic properties. In this study, 30 samples of bee pollen from Apis mellifera apiaries in three mesoregions of Alagoas (Brazil) - Mata Atlântica, South Coast and Caatinga, were collected during the dry season of 2008/09 and analysed. Mata Atlântica and Caatinga had good production of bee pollen. In the same season, Mata Atlântica contained a higher diversity of pollen types for feeding bees with a predominance of herbaceous pollen (63%), whereas the Caatinga samples contained monofloral pollen. Physicochemical data were analysed with the nonparametric Kruskal-Wallis statistical test. The Caatinga samples were analysed to determine their contents of total phenolic compounds (25.85 ± 10.80 mg gallic acid eq/g) and flavonoids (45.62 ± 32.19 mg quercetin eq/g) and their antioxidant activity (for instance, 70.62 ± 4.50% in the DPPH test), which were possibly affected by the environmental conditions of this biome.

The combined effects of a monotonous diet and exposure to thiamethoxam on the performance of bumblebee micro-colonies

There is a pressing need to better understand the factors contributing to declines of wild pollinators such as bumblebees. Many different contributors have been postulated including: loss of flower-rich habitats and nesting sites; monotonous diets; impacts of invasive pathogens; exposure to pesticides such as neonicotinoids. Past research has tended to investigate the impacts of these stressors in isolation, despite the increasing recognition that bees are simultaneously exposed to a combination of stressors, with potentially additive or synergistic effects. No studies to date have investigated the combined effects of a monotonous diet and exposure to pesticides. Using queenless micro-colonies of Bombus terrestris audax, we examined this interaction by providing bees with monofloral or polyfloral pollen that was either contaminated with field-realistic levels of thiamethoxam, a commonly used neonicotinoid, or not contaminated. Both treatments were found to have a significant effect on various parameters relating to micro-colony performance. Specifically, both pesticide-treated micro-colonies and those fed monofloral pollen grew more slowly than those given polyfloral pollen or pollen without pesticides. The two factors appeared to act additively. Micro-colonies given monofloral pollens also exhibited lower reproductive efforts and produced smaller drones. Although further research is needed to examine whether similar effects are found in whole colonies, these findings increase our understanding of the likely effects of multiple stressors associated with agricultural intensification on bee declines.

Characterization of Coffea arabica monofloral honey from Espírito Santo, Brazil

In this study, samples of coffee honey produced in Espírito Santo State, Brazil, were characterized based on their melissopalynology, physicochemical and nutritional properties, and mineral and caffeine contents. The caffeine content in the nectar from coffee flowers was measured by high performance liquid chromatography (HPLC). Blends of honey were obtained from three Coffea arabica crops, each with 10 colonies of Africanized Apis mellifera. All honey samples contained monofloral (75–78%) pollen belonging to C. arabica. Physicochemical parameters (total acidity, pH, moisture, dry matter, ash, and qualitative hydroxymethylfurfural) were within the approved limits established by EU legislation. Coffee honey contains high levels of ascorbic acid (294.68mgkg−1) and low amounts of total flavonoids (3.51±0.18mgQEkg−1). The most abundant minerals were potassium and calcium (962.59±154.3 and 343.75±25.56mgkg−1, respectively). The caffeine content in coffee nectar (1.64mgkg−1) was approximately 8-fold lower than that in honey (12.02±0.81mgkg−1).

Bee Pollen in Transylvania (Romania): Palynological Characterization and ORACFL Values of Lipophilic and Hydrophilic Extracts of Monofloral Pollen Pellets

Bee Pollen in Transylvania (Romania): Palynological Characterization and ORACFL Values of Lipophilic and Hydrophilic Extracts of Monofloral Pollen Pellets

Bias to pollen odors is affected by early exposure and foraging experience

In many pollinating insects, foraging preferences are adjusted on the basis of floral cues learned at the foraging site. In addition, olfactory experiences gained at early adult stages might also help them to initially choose food sources. To understand pollen search behavior of honeybees, we studied how responses elicited by pollen-based odors are biased in foraging-age workers according to (i) their genetic predisposition to collect pollen, (ii) pollen related information gained during foraging and (iii) different experiences with pollen gained at early adult ages. Bees returning to the hive carrying pollen loads, were strongly biased to unfamiliar pollen bouquets when tested in a food choice device against pure odors. Moreover, pollen foragers’ orientation response was specific to the odors emitted by the pollen type they were carrying on their baskets, which suggests that foragers retrieve pollen odor information to recognize rewarding flowers outside the hive. We observed that attraction to pollen odor was mediated by the exposure to a pollen diet during the first week of life. We did not observe the same attraction in foraging-age bees early exposed to an artificial diet that did not contain pollen. Contrary to the specific response observed to cues acquired during foraging, early exposure to single-pollen diets did not bias orientation response towards a specific pollen odor in foraging-age bees (i.e. bees chose equally between the exposed and the novel monofloral pollen odors). Our results show that pollen exposure at early ages together with olfactory experiences gained in a foraging context are both relevant to bias honeybees’ pollen search behavior.

Influence of Pollen Nutrition on Honey Bee Health: Do Pollen Quality and Diversity Matter?

Honey bee colonies are highly dependent upon the availability of floral resources from which they get the nutrients (notably pollen) necessary to their development and survival. However, foraging areas are currently affected by the intensification of agriculture and landscape alteration. Bees are therefore confronted to disparities in time and space of floral resource abundance, type and diversity, which might provide inadequate nutrition and endanger colonies. The beneficial influence of pollen availability on bee health is well-established but whether quality and diversity of pollen diets can modify bee health remains largely unknown. We therefore tested the influence of pollen diet quality (different monofloral pollens) and diversity (polyfloral pollen diet) on the physiology of young nurse bees, which have a distinct nutritional physiology (e.g. hypopharyngeal gland development and vitellogenin level), and on the tolerance to the microsporidian parasite Nosema ceranae by measuring bee survival and the activity of different enzymes potentially involved in bee health and defense response (glutathione-S-transferase (detoxification), phenoloxidase (immunity) and alkaline phosphatase (metabolism)). We found that both nurse bee physiology and the tolerance to the parasite were affected by pollen quality. Pollen diet diversity had no effect on the nurse bee physiology and the survival of healthy bees. However, when parasitized, bees fed with the polyfloral blend lived longer than bees fed with monofloral pollens, excepted for the protein-richest monofloral pollen. Furthermore, the survival was positively correlated to alkaline phosphatase activity in healthy bees and to phenoloxydase activities in infected bees. Our results support the idea that both the quality and diversity (in a specific context) of pollen can shape bee physiology and might help to better understand the influence of agriculture and land-use intensification on bee nutrition and health.

Role of food quality in bee susceptibility to fipronil and clothianidin

Pollen is the honey bee’s main protein supply. Newly emerged bees need pollen alimentation to guarantee correct development of physiological conditions and breeding potential. To ensure functional and efficient adult bees not only the quantity but also the quality of pollen is important: pollen of different plant species vary in nutritional quality for honey bees. Previous studies showed that a protein alimentation with pollen mixture is more adequate for bees than monofloral pollen. The kind of pollen collected by bees is in close relationship with the vegetation spectrum of the hive surrounding area. Thus, if the bee colony is surrounded by areas characterised by intensive agriculture e.g. the Po Valley in Italy it may mainly collect monofloral pollen. In these areas, use of pesticides is generally widespread. The present study is based on the hypothesis that the quality of pollen available for the honey bee colony may influence the bee susceptibility to the intoxication by pesticides. For this reason, the same pesticide treatment could cause negligible or significant damages in relation to the availability of high-quality pollen (high amino acid diversity and high protein content). In the experimental apiary, in order to obtain newly emerged bees of the same age, the queen bee was isolated on a comb in a queen-excluding cage for about 30 hours. Subsequently the queen bee was removed from the cage and the comb was left isolated for another three days, to avoid further egg laying. The comb was incubated inside the beehive for 20 days in order to guarantee the most natural conditions, then it was moved to an emerging cage and kept at 34,5°C. The bees were incubated at this temperature until the end of the test. At the beginning of the emergence the bees were fed ad libitum with water, organic Robinia honey and a kind of pollen in relation to the thesis: Zea mays, Papaver, Cruciferae, Trifolium, Taraxacum or a mixture of pollen. Thus groups of bees provided with different pollen diets were obtained. On the 9 day, the bees were divided into groups of 20 individuals in small test cages in which clothianidin or fipronil pesticides considered as one of the possible causes of the recent colony losses in sucrose syrup (50%) were administered. Once the bees consumed completely the test solution, sucrose syrup (50%) was supplied ad libitum. Bee mortality was recorded and the LD50 of the active ingredients was calculated in relationship to the alimentation quality. In conclusion, the influence of the quality of protein nourishment provided during the first days of adult life on the response to intoxication by clothianidin and fipronil was shown as evidence. Bees fed with low-quality pollen (low amino acid diversity and low protein content) seem to be more susceptible to pesticide intoxication and other stress factors than bees fed with high-quality pollen.