Evaluation of the floral rewards of Aloe greatheadii var davyana (Asphodelaceae), the most important indigenous South African bee plant

The most important indigenous bee plant in South Africa is the winter flowering Aloe greatheadii var davyana, with a widespread distribution across the summer rainfall region. Beekeepers commonly move their hives to the "aloe fields" during winter, using the strong pollen and nectar flow for colony growth, queen rearing and honey production. In spite of its importance for the bee industry, no complete pollen analysis is available and, except for the popular bee literature, little is known about nectar production or pollinators. The aim of the study was therefore to evaluate the floral rewards of this aloe and to investigate the importance of these resources for honeybees. We analysed fresh, bee-collected and stored aloe pollen for its nutritional content (not previously done for any plant species). Addition of nectar and glandular secretions leads to an increase in water and carbohydrate content and a decrease in protein and lipid content. All the essential amino acids, except tryptophan, met or exceeded the minimum levels for honeybee development. In worker bees in queenright colonies, ovarian development is greater on aloe than on sunflower pollen, which may be explained by the exceptionally high protein content and high extraction efficiency during digestion. In assessing the nectar resource, we investigated the nectary structure and nectar presentation of two species belonging to different sections of the genus Aloe, A. castanea and A. greatheadii var davyana, but anatomical differences were not related to the nectar production. We looked at variation in nectar volume and concentration of A. greatheadii var davyana on various levels, from within the flowers to across the summer rainfall area. Nectar was continuously available and, although dilute (mean concentration 18.6%), the nectar of A. greatheadii var davyana is more concentrated than that of other Aloe species, making it an ideal source of energy and water for honeybees. Utilisation of dilute nectar by bees requires elimination of much excess water. We sampled crop contents of nectar foragers to determine if changes in nectar concentration occurred after collection and before unloading in the hive. Contrary to the common assumption that nectar is either unchanged or slightly diluted during transport, we observed a dramatic increase in concentration and a decrease in volume between the flowers and the hive. Bees may be foraging primarily to get enough water for their physiological needs. Using miniaturised data loggers, we showed that bees are able to adjust nest humidity within sub-optimal limits, in addition to efficient regulation of hive temperature. Humidity levels are influenced by trade-offs with regulation of temperature and respiratory gas exchanges. Although the dilute nectar and pinkish red tubular flowers are characteristic of bird-pollination, exclusion experiments showed that bees are the primary pollinators of A. greatheadii var davyana. This contrasts with other Aloe species which are pollinated by sunbirds and other passerine birds, but highlights the two-way interaction between the bees and the aloes.Thesis (PhD (Entomology))--University of Pretoria, 2008.Zoology and Entomologyunrestricte

Honey bees save energy in honey processing by dehydrating nectar before returning to the nest

Honey bees process nectar into honey by active evaporation on the tongue and passive evaporation involving nest ventilation and fanning behaviour, as well as enzymatic action. The elimination of excess water from nectar carries considerable energetic costs. The concentration of the nectar load is assumed to remain constant during transport. However, some of this water elimination may occur before foragers return to the nest and pass their nectar loads to receiver bees. In honey bees captured while foraging in Macadamia orchards, we show that the nectar in their crops has approximately twice the sugar concentration of the fresh nectar in fowers. This was true for four Macadamia cultivars, with up to 75% of the initial water content being removed. There is a further concentration increase in the crops of returning bees captured at the hive entrance. The only possible route of water elimination from the crop is via evaporation from the mouthparts. We calculate the savings in honey processing costs to be on average 35 times more than the reduction in fight costs due to reduced body mass. Pre-concentration of nectar in foraging honey bees may be widespread, and of crucial importance for honey storage.SAMAChttps://www.nature.com/srepZoology and Entomolog

Digestibility and nutritional value of fresh and stored pollen for honey bees (Apis mellifera scutellata)

Pollen, the main protein source for honey bees, is mixed with regurgitated nectar or honey during collection and then stored as ‘bee bread’ before its consumption, mainly by young nurse workers. It has been suggested that storage of pollen improves its nutritional value and digestibility, but there is little evidence for such changes. We fed two fresh pollen types of different protein content (aloe and sunflower), and two stored pollen types (sunflower and a mixed pollen), to young caged worker bees. We measured daily consumption of pollen and sucrose solution, and survival after 14 days. At day 14 we recorded ovarian activation and extraction efficiency, by counting empty pollen grains in the rectal contents. Extraction efficiency is a measure of pollen digestibility. Contrary to our predictions, bees did not consume more fresh sunflower pollen than fresh aloe pollen to compensate for the lower protein content of sunflower pollen. In addition, they did not consume less sucrose solution when fed stored pollen diets that are already enriched in sugar. Consumption of stored sunflower pollen resulted in a low protein to carbohydrate (P:C) intake. Survival and ovarian activation were higher on diets giving higher P:C intakes. Extraction efficiency was high (up to 99%) for all pollen diets, and comparison of fresh and stored sunflower pollen showed that storage did not make it easier to digest. Changes to pollen during storage do not confer obvious benefits to honey bees.The National Research Foundation of South Africa.http://www.elsevier.com/locate/jinsphys2019-05-01hj2018Zoology and Entomolog

Resistance of developing honeybee larvae during chronic exposure to dietary nicotine

The effects of pesticides on honeybee larvae are less understood than for adult bees, even though larvae are chronically exposed to pesticide residues that accumulate in comb and food stores in the hive. We investigated how exposure to a plant alkaloid, nicotine, affects survival, growth and body composition of honeybee larvae. Larvae of Apis mellifera scutellata were reared in vitro and fed throughout development on standard diets with nicotine included at concentrations from 0 to 1000 μg/100 g diet. Overall mortality across all nicotine treatments was low, averaging 9.8 % at the prepupal stage and 18.1 % at the whiteeyed pupal stage, but survival was significantly reduced by nicotine. The mass of prepupae and white-eyed pupae was not affected by nicotine. In terms of body composition, nicotine affected water content but did not influence either protein or lipid stores of white-eyed pupae. We attribute the absence of consistent negative effects of dietary nicotine to detoxification mechanisms in developing honeybees, which enable them to resist both natural and synthetic xenobiotics.The BBSRC, NERC, the Wellcome Trust,Defra, and the Scottish Government under the Insect Pollinators Initiative (BB/I000968/1), National Research Foundation of South Africa and the University of Pretoria.http://www.elsevier.com/locate/jinsphyshb201

Honeybee health in Africa - a review

Honeybee (Apis mellifera L.) pathogens and parasites and the negative effects thereof on honeybee populations remain an issue of public concern and the subject of active research. Africa with its high genetic diversity of honeybee sub-species and large wild population is also exposed to various factors responsible for colony losses in other parts of the world. Apart from the current American foulbrood epidemic in theWestern Cape of South Africa, no large-scale colony losses have been reported elsewhere on the continent. We discuss the presence of pathogens, parasites, pests and predators of African honeybees as well as the threats they face in relation to habitat changes arising from the impact of increased human populations. In addition, we discuss current efforts aimed at protecting and promoting the health of African honeybees.SouthAfrican National Research Foundation (NRF) and the University of Pretoria.http://link.springer.com/journal/135922017-05-31hb2016Zoology and Entomolog

Antibiotic treatment impairs protein digestion in the honeybee, Apis mellifera

Nutritional stress due to habitat transformation and loss is one of several factors contributing to current declines in global bee populations. Bees obtain protein from pollen, which in honeybees is consumed and digested by nurse bees. They then distribute the protein to the rest of the colony in the form of hypopharyngeal gland secretions. Little is known of how efficiently honeybees digest protein. Moreover, antibiotics are used by beekeepers as in-hive treatments for diseases and may interfere with microbial contributions to protein digestion. Caged, newly emerged workers of Apis mellifera scutellata were fed caseinate as protein source, to investigate the effects of protein intake and antibiotic treatment on digestive efficiency. These workers were fed protein:carbohydrate ratios of 1:120, 1:50 and 1:15 or pure sucrose for 9 days. Half the cages received dietary oxytetracycline at a concentration used by beekeepers. Antibiotic exposure did not affect survival or protein consumption. Protein digestive efficiency increased with increasing levels of protein in the diet, although a decrease would have contributed to maintaining nutrient balance. Importantly, we show that antibiotic exposure impaired protein digestive efficiency, especially on low-protein diets. This may be particularly important when colonies are restricted to a single protein deficient source of pollen.The University of Pretoria and by the National Research Foundation of South Africa.http://link.springer.com/journal/135922020-12-02hj2020BiochemistryGeneticsMicrobiology and Plant PathologyZoology and Entomolog

Effects of a neonicotinoid pesticide on thermoregulation of African honey bees (Apis mellifera scutellata)

Thiamethoxam is a widely used neonicotinoid pesticide that, as agonist of the nicotinic acetylcholine receptors, has been shown to elicit a variety of sublethal effects in honey bees. However, information concerning neonicotinoid effects on honey bee thermoregulation is lacking. Thermoregulation is an essential ability for the honey bee that guarantees the success of foraging and many in-hive tasks, especially brood rearing. We tested the effects of acute exposure to thiamethoxam (0.2, 1, 2ng/bee) on the thorax temperatures of foragers exposed to low (22°C) and high (33°C) temperature environments. Thiamethoxam significantly altered honey bee thorax temperature at all doses tested; the effects elicited varied depending on the environmental temperature and pesticide dose to which individuals were exposed. When bees were exposed to the high temperature environment, the high dose of thiamethoxam increased their thorax temperature 1-2h after exposure. When bees were exposed to the low temperature, the higher doses of the neonicotinoid reduced bee thorax temperatures 60-90min after treatment. In both experiments, the neonicotinoid decreased the temperature of bees the day following the exposure. After a cold shock (5min at 4°C), the two higher doses elicited a decrease of the thorax temperature, while the lower dose caused an increase, compared to the control. These alterations in thermoregulation caused by thiamethoxam may affect bee foraging activity and a variety of in-hive tasks, likely leading to negative consequences at the colony level. Our results shed light on sublethal effect of pesticides which our bees have to deal with.This work was supported by the University of Pretoria, the National Research Foundation of South Africa, the BBSRC Insect Pollinators initiative (BB/1000968/1) and the Marco Polo scholarship, awarded by University of Bologna to ST.http://www.elsevier.com/locate/jinsphys2017-10-31hb2016Zoology and Entomolog

Proteomic and metabolomic analysis reveals rapid and extensive nicotine detoxification ability in honey bee larvae

Despite potential links between pesticides and bee declines, toxicology information on honey bee larvae (Apis mellifera) is scarce and detoxification mechanisms in this development stage are virtually unknown. Larvae are exposed to natural and synthetic toxins present in pollen and nectar through consumption of brood food. Due to the characteristic intensive brood care displayed by honey bees, which includes progressive feeding throughout larval development, it is generally assumed that larvae rely on adults to detoxify for them and exhibit a diminished detoxification ability. We found the opposite. We examined the proteomic and metabolomic responses of in vitro reared larvae fed nicotine (an alkaloid found in nectar and pollen) to understand how larvae cope on a metabolic level with dietary toxins. Larvae were able to effectively detoxify nicotine through an inducible detoxification mechanism. A coordinated stress response complemented the detoxification processes, and we detected significant enrichment of proteins functioning in energy and carbohydrate metabolism, as well as in development pathways, suggesting that nicotine may promote larval growth. Further exploration of the metabolic fate of nicotine using targeted mass spectrometry analysis demonstrated that, as in adult bees, formation of 4-hydroxy-4-(3-pyridyl) butanoic acid, the result of 2’C-oxidation of nicotine, is quantitatively the most significant pathway of nicotine metabolism. We provide conclusive evidence that larvae are capable of effectively catabolising a dietary toxin, suggesting that increased larval sensitivity to specific toxins is not due to diminished detoxification abilities. These findings broaden the current understanding of detoxification biochemistry at different organizational levels in the colony, bringing us closer to understanding the capacity of the colony as a superorganism to tolerate and resist toxic compounds, including pesticides, in the environment.This work was funded jointly by a grant from the Biotechnology and Biological Sciences Research Council (BBSRC), Natural Environment Research Council (NERC), the Wellcome Trust, Defra, and the Scottish Government under the Insect Pollinators Initiative (BB/ I000968/1). We also acknowledge the support of the National Research Foundation of South Africa (73671) and the University of Pretoria.http://www.elsevier.com/locate/ibmb2018-03-31hb2017BiochemistryZoology and Entomolog

Standard epidemiological methods to understand and improve Apis mellifera health

In this paper, we describe the use of epidemiological methods to understand and reduce honey bee morbidity and mortality. Essential terms are presented and defined and we also give examples for their use. Defining such terms as disease, population, sensitivity, and specificity, provides a framework for epidemiological comparisons. The term population, in particular, is quite complex for an organism like the honey bee because one can view “epidemiological unit” as individual bees, colonies, apiaries, or operations. The population of interest must, therefore, be clearly defined. Equations and explanations of how to calculate measures of disease rates in a population are provided. There are two types of study design; observational and experimental. The advantages and limitations of both are discussed. Approaches to calculate and interpret results are detailed. Methods for calculating epidemiological measures such as detection of rare events, associating exposure and disease (Odds Ratio and Relative Risk), and comparing prevalence and incidence are discussed. Naturally, for beekeepers, the adoption of any management system must have economic advantage. We present a means to determine the cost and benefit of the treatment in order determine its net benefit. Lastly, this paper presents a discussion of the use of Hill’s criteria for inferring causal relationships. This framework for judging cause-effect relationships supports a repeatable and quantitative evaluation process at the population or landscape level. Hill’s criteria disaggregate the different kinds of evidence, allowing the scientist to consider each type of evidence individually and objectively, using a quantitative scoring method for drawing conclusions. It is hoped that the epidemiological approach will be more broadly used to study and negate honey bee disease.The COST Action FA0803http://www.ibra.org.uk/am201

Métodos para la investigación de la loque americana

American foulbrood is one of the most devastating diseases of the honey bee. It is caused by the spore-forming, Gram-positive rod-shaped bacterium Paenibacillus larvae. The recent updated genome assembly and annotation for this pathogen now permits in-depth molecular studies. In this paper, selected techniques and protocols for American foulbrood research are provided, mostly in a recipe-like format that permits easy implementation in the laboratory. Topics covered include: working with Paenibacillus larvae, basic microbiological techniques, experimental infection, and “’omics” and other sophisticated techniques. Further, this chapter covers other technical information including biosafety measures to guarantee the safe handling of this pathogen.La loque americana es una de las enfermedades más devastadoras de la abeja melífera, causada por el bacilo, formador de esporas Grampositivo Paenibacillus larvae. El reciente ensamblaje y anotación del genoma de este patógeno permite actualmente la realización de profundos estudios moleculares. En este trabajo, se proporcionan técnicas y protocolos seleccionados para la investigación de la loque americana, principalmente bajo la forma de protocolos de trabajo con una estructura similar al de las recetas, para facilitar su implementación en el laboratorio. Los temas desarrollados incluyen: el trabajo con Paenibacillus larvae, técnicas básicas microbiológicas, la infección experimental, y "'ómicas" y otras técnicas sofisticadas. Además, este capítulo abarca otro tipo de información técnica, incluyendo medidas de bioseguridad para garantizar la seguridad en el manejo de este patógeno.Trabajo publicado en Dietemann, V.; Ellis, J. D.; Neumann, P. (eds.) The Coloss Beebook, Volume II: standard methods for Apis mellifera pest and pathogen research. Journal of Apicultural Research, 52(1).Facultad de Ciencias Agrarias y Forestale