Hannelie Human

Miscellaneous standard methods for Apis mellifera research

Summary A variety of methods are used in honey bee research and differ depending on the level at which the research is conducted. On an individual level, the handling of individual honey bees, including the queen, larvae and pupae are required. There are different methods for the immobilising, killing and storing as well as determining individual weight of bees. The precise timing of developmental stages is also an important aspect of sampling individuals for experiments. In order to investigate and manipulate functional processes in honey bees, e.g. memory formation and retrieval and gene expression, microinjection is often used. A method that is used by both researchers and beekeepers is the marking of queens that serves not only to help to locate her during her life, but also enables the dating of queens. Creating multiple queen colonies allows the beekeeper to maintain spare queens, increase brood production or ask questions related to reproduction. On colony level, very useful techniques are the measurement of intra hive mortality using dead bee traps, weighing of full hives, collecting pollen and nectar, and digital monitoring of brood development via location recognition. At the population level, estimation of population density is essential to evaluate the health status and using beelines help to locate wild colonies. These methods, described in this paper, are especially valuable when investigating the effects of pesticide applications, environmental pollution and diseases on colony survival.

The importance of protein type and protein to carbohydrate ratio for survival and ovarian activation of caged honeybees (Apis mellifera scutellata)

Pollen is the natural source of protein for bees and it is commonly assumed that a high protein content in pollen is beneficial. Investigation of the optimal nutrient ratio for honeybees was prompted by our earlier study showing surprisingly high mortality in caged honeybees fed with the protein-rich pollen of Aloe greatheadii var davyana, although field bees experience optimal growth when feeding on this pollen. We tested the effect of different protein sources and different protein:carbohydrate (P:C) ratios on the survival and ovarian activation of caged bees. Bees fed casein showed consistently higher survival than those fed royal jelly or aloe pollen, regardless of P:C ratios. They survived longer on lower P:C ratios and longest on a pure carbohydrate diet. The greatest ovarian activation was recorded for bees fed royal jelly in a 1:3 P:C ratio, showing the superior quality of royal jelly for supporting development.ZusammenfassungDie Hauptnahrungsquellen für Honigbienen sind Nektar, der ihnenn hauptsächlich als Kohlenhydratquelle zur Energiegewinnung dient, und Pollen, der die hauptsächliche Proteinquelle darstellt und aus dem sie ausserdem Vitamine, Mineralien und Lipide gewinnen. Proteine sind vor allem für das rasche Wachstum der Larven und den Abschluss der Entwicklung erforderlich, und junge Arbeiterinnen füttern demzufolge die Larven mit Gelée royal, eingelagertem Pollen und Honig. Trotzdem sind unsere Kenntnisse gering über die Beziehungen der Makronährstoffe in der Diet der Honigbienen und deren physiologische Effekte. Wir untersuchten hier die Hypothese, ob eine Verringerung des Protein/Kohlenhydrat-Verhältnisses (P:C-Verhältnis), z.B. bedingt durch eine relative Anreicherung der Nahrung mit Kohlenhydraten, die Überlebensrate und die Ovaraktivität junger Arbeiterinnen erhöhen könnte. Dazu hielten wir jeweils 100 Arbeiteinnen in Käfigen in einem Brutschrank unter kontrollierten Bedingungen. Wir verabreichten ihnen jeweils eine von 11 zu testenden Diäten und untersuchten über einen Zeitraum von 14 Tagen die Überlebensraten. Danach wurden alle Bienen zur Erfassung der Ovarentwicklung abgetötet. Die Wichtigkeit des Kohlenhydratgehalts für das Überleben der Bienen ist unabhängig vom verabreichten Proteintyp (Abb. 1). Bienen, die auschschliesslich Proteine erhielten, zeigten eine deutlich verkürzte Lebensdauer, ganz im Gegensatz zu solchen, die ausschlieslich Sacharose erhielten. Der Unterschied zwischen diesen beiden Kontrolldiäten ist hochsignifikant (Tab. II). Innerhalb der Bienen, die den 14-täigen Untersuchungszeitraum überlebten. zeigten diejenigen, die Gelée royale in einen 1:3 P:C-Verhältnis erhalten hatten, den höchsten Grad der Ovaraktivierung (Abb. 2), mit einem mittleren Wert von Grad 3. Innerhalb der drei getesteten Proteinquellen zeigte Casein die besten Werte in Bezug auf die Überlebensraten, und zwar bei allen jeweiligen P:C-Verhältnissen. Da Gelée royale für alle essentiellen Aminosäuren über den Minimalanforderungen liegt und da Casein diese Anforderungen ebenfalls erfüllt, ist es unwahrscheinlich, dass die Aminosäurenzusammensetzung die niedrigere Mortalität bei Caseindiäten erklären kann. Die niedrigsten Úberlebensraten hatten wir für Pollen von A. greatheadii var davyana, der von Bienen gesammelt war. Dies mag daran liegen, dass sich bei den gekäfigten Bienen nicht abbaubare und/oder toxische Substsanzen im Darm ansammeln.Unsere Ergebnisse stehen in Einklang mit denen von Human et al. (2007), denenzufolge gekäfigte Bienen, die mit Aloepollen gefüttert worden waren, eine höhere Mortalität und eine geringere Ovaraktivität zeigten als Bienen, die Sonnenblumenpollen erhalten hatten. Dies könnte auf soziale Interaktionen innerhalb der gekäfigten Bienen zurückzuführen sein. Dominante Arbeiterinnen, die ihre Ovarien aktivieren, nutzen den “sozialen Nahrungsweg” und werden von untergeordneten Arbeiterinnen gefüttert, die Pollen verdauen und Gelée royale synthetisieren. Wenn diese untergeordneten Arbeiterinnen beispielsweise zu schnell aufgund der negativen Effekte von Pollen sterben, bricht die Nahrungskette zusammen und führt im Gesamtbild zu niedrigeren Überlebensund Ovaraktivierungsraten. In einer Feldsituation hingegen kann vermutlich der Proteinüberschuss in A. greatheadii var davyana Pollen gegenüber anderen Nahrungskompenenten durch das Vorhandensein ausreichenden Nektars verdünnt werden. Ausserdem sind unter Feldbedingungen stets genügend Arbeiterinnen vorhanden, um eventuelle Ausfälle in der Kette des “sozialen Nahrungswegs” zu kompensieren.

Do honeybees, Apis mellifera scutellata, regulate humidity in their nest?

Honeybees are highly efficient at regulating the biophysical parameters of their hive according to colony needs. Thermoregulation has been the most extensively studied aspect of nest homeostasis. In contrast, little is known about how humidity is regulated in beehives, if at all. Although high humidity is necessary for brood development, regulation of this parameter by honeybee workers has not yet been demonstrated. In the past, humidity was measured too crudely for a regulation mechanism to be identified. We reassess this issue, using miniaturised data loggers that allow humidity measurements in natural situations and at several places in the nest. We present evidence that workers influence humidity in the hive. However, there are constraints on potential regulation mechanisms because humidity optima may vary in different locations of the nest. Humidity could also depend on variable external factors, such as water availability, which further impair the regulation. Moreover, there are trade-offs with the regulation of temperature and respiratory gas exchanges that can disrupt the establishment of optimal humidity levels. As a result, we argue that workers can only adjust humidity within sub-optimal limits.

A survey of managed honey bee colony losses in the Republic of South Africa–2009 to 2011

Summary This study reports honey bee, Apis mellifera L., colony losses that occurred in South Africa over two consecutive years. The total losses were 29.6% (95% CI: 22.8–37.5) in 2009–2010 and 46.2% (95% CI: 37.3–55.0) in 2010–2011. Furthermore, the study shows that the capensss worker social parasite, a problem unique to southern Africa, is the main perceived cause, and could explain the significant differences in the number of losses between beekeepers using the subspecies A. m. scutellata and those using the subspecies A. m. capensis. In contrast to previous studies in North America and Europe, we find a significant negative effect of migratory beekeeping practices on the extent of colony losses. Migratory beekeepers lost on average more colonies (35.5% (95% CI 29.7–47.2)) than did stationary beekeepers (17.2% (95% CI 11.2–22.3)). This was especially pronounced when the beekeepers were migrating for the pollination of apples/cherries, eucalyptus, onions and/or sunflowers. The major beekeeper-perceived causes of mortality were small hive beetles, varroa mites, absconding (non-reproductive swarming), and chalkbrood disease. Those listing chalkbrood disease lost significantly fewer colonies than those who did not list chalkbrood. The exact mechanism for this difference is unknown, and may be related to other beekeeping practices that correlate with finding chalkbrood infections—namely more intensive inspection and management.

Seasonal prevalence of pathogens and parasites in the savannah honeybee (Apis mellifera scutellata)

The loss of Apis mellifera L. colonies in recent years has, in many regions of the world, been alarmingly high. No single cause has been identified for these losses, but the interactions between several factors (mostly pathogens and parasites) have been held responsible. Work in the Americas on honeybees originating mainly from South Africa indicates that Africanised honeybees are less affected by the interplay of pathogens and parasites. However, little is known about the health status of South African honeybees (A. m. scutellata and A. m. capensis) in relation to pathogens and parasites. We therefore compared the seasonal prevalence of honeybee pathogens (viruses, bacteria, fungi) and parasites (mites, bee lice, wax moth, small hive beetles, A. m. capensis social parasites) between sedentary and migratory A. m. scutellata apiaries situated in the Gauteng region of South Africa. No significant differences were found in the prevalence of pathogens and parasites between sedentary and migratory apiaries. Three (Black queen cell virus, Varroa destructor virus 1 and Israeli acute paralysis virus) of the eight viruses screened were detected, a remarkable difference compared to European honeybees. Even though no bacterial pathogens were detected, Nosema apis and Chalkbrood were confirmed. All of the honeybee parasites were found in the majority of the apiaries with the most common parasite being the Varroa mite. In spite of hosting few pathogens, yet most parasites, A. m. scutellata colonies appeared to be healthy.

Chemical composition of the ‘low quality’ pollen of sunflower (Helianthus annuus, Asteraceae)

The nutritional needs of bees are receiving renewed attention in the context of declining bee populations and changes in land use that threaten floral resources. We present a comprehensive analysis of the nutritional composition of sunflower (Helianthus annuus L.) pollen, comparing hand-collected, bee-collected and stored pollen. As found in previous studies, the protein content of sunflower pollen was relatively low compared to other important bee forage plants. In the cultivars tested, two essential amino acids, methionine and tryptophan, are likely to be below the minimum requirements for honeybees. Fatty acid composition showed lauric acid to be most abundant, followed by palmitic and α-linolenic acids. While sunflower offers abundant and accessible pollen, its quality may hinder bee development when it is an exclusive pollen source, and the cultivars of such mass-flowering crops may vary in value for pollinators.

Digestion of maize and sunflower pollen by the spotted maize beetle Astylus atromaculatus (Melyridae): is there a role for osmotic shock?

We investigated the mechanism and efficiency of digestion of two types of pollen, maize, Zea mays, and sunflower, Helianthus annuus, by the spotted maize beetle, Astylus atromaculatus (Melyridae). We found similar and high extraction efficiencies, but different mechanisms of digestion. Osmotic shock was apparently involved in digestion of the large and thin-walled maize pollen grains. In the anterior midgut most maize pollen grains were already ruptured, in contrast with the intact exines of sunflower pollen, which suggests another mechanism of digestion for the latter, such as enzymatic action. We investigated the effect of osmotic shock on maize pollen in vitro by looking at the behavior of pollen grains in varying osmotic concentrations. Maize pollen grains burst in both distilled water and sugar solutions of various concentrations, and the amount of rupturing decreased with an increase in sugar concentration. Digestion of maize pollen was much slower in honeybees than in spotted maize beetles. Maize pollen bursts early in the midgut of maize beetles, but remains intact in honeybees: this suggests that osmotic shock may not be as important for honeybees as previously suggested.

Bees get a head start on honey production

Nectar concentration is assumed to remain constant during transport by honeybees between flowers and hive. We sampled crop contents of nectar foragers on Aloe greatheadii var. davyana, a major winter bee plant in South Africa. The nectar is dilute (approx. 20% w/w), but the crop contents of bees captured on flowers are significantly more concentrated. In returning foragers, the concentration increases further to 38–40%, accompanied by a volume decrease. The doubling of sugar concentration suggests that nectar is regurgitated onto the tongue and evaporated during foraging and on the return flight. Processing of the dilute nectar into honey thus begins early, aided by low ambient humidities. This has implications for honeybee thermoregulation, water balance and energetics during foraging, and for the communication of nectar quality to recruits.

Flower structure and nectar availability in Aloe greatheadii var davyana : an evaluation of a winter nectar source for honeybees

The winter‐flowering Aloe greatheadii var. davyana is a major indigenous bee plant in South Africa, widely distributed across the northern summer rainfall areas. Migratory beekeepers take advantage of its highly nutritious pollen for colony increase and strong nectar flow for honey production. We looked at variation on different levels in assessing this nectar resource for bees. There were no significant differences in nectar volume and concentration between the basal swelling (bulb) and the floral tube, only between flower stages. Nectar was continuously available, with volume and concentration remaining relatively constant throughout the day despite pronounced diurnal temperature changes and very low afternoon humidities. Bee foraging reduced mean nectar volumes in unscreened flowers by 50%, from 30.7 to 14.7 μL; bees are unable to access nectar in the bulb. Nectar volume was lowest and nectar concentration highest late in the flowering season, while the highest sugar content (3.54 mg per flower) was recorded in the middle of the flowering season. Aloe greatheadii var. davyana nectar, although dilute from a bee perspective (ca. 20% w/w), is more concentrated than that of many bird‐pollinated Aloe species and is an ideal source of energy and water for honeybees during dry winter months.

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 the Western 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.