Honeybee evolution : royal jelly proteins help queen larvae to stay on top

A new study shows that, in honey bees, the main role of certain proteins in royal jelly is to ensure that the larva stays in its cell, thereby allowing it to develop into a queen.https://www.journals.elsevier.com/current-biology2019-04-23hj2018Zoology and Entomolog

Reproductive conflicts in honeybee colonies

In advanced eusocial hymenopteran societies workers have ovaries and can lay eggs, but are unable to mate. Workers are more related to their own offspring than to every other member of the colony. So worker reproduction contains both worker-worker and worker-queen conflict. The queen- worker conflict is discussed elsewhere, but if the queen mates with more than two males, worker policing should be selected to lower potential conflicts. However in the Cape honeybee it was predicted that worker policing is absent or less expressed than in other honeybee subspecies, because workers produce female offspring thelytokously. So laying workers and their offspring are nearly genetically identical, which results in the fact that other workers are as related to workers derived from eggs laid by the queen as laid by a worker. However, worker reproduction may be costly and therefore worker policing could be an evolutionary adaptation in the Cape honeybee to lower the costs derived from laying worker activity. Indeed, Cape honeybee colonies show efficient egg removal behaviour, suggesting that other factors like colony efficiency could favour egg removal behaviour. Since egg removal behaviour is a colony phenomenon, factors that affect colony performance could also affect egg removal behaviour. Egg removal behaviour was considerably affected by environmental changes, indicating that other tasks have a higher priority than egg removal behaviour. Thousands of queenright colonies of the neighbouring subspecies (A. m. scutellata) were taken over by laying A. m. capensis workers, showing that A. m. capensis workers are facultative social parasites. These observations strongly indicate that laying workers of A. m. capensis are able to evade worker policing and the inhibitory effects of the queen pheromones, but what potential strategies could these laying workers use to increase the survival of their eggs and evade the queen? On the one hand, egg removal behaviour is variable. One behavioural strategy of laying workers to achieve successful reproduction could be that they lay during periods with low egg removal behaviour. On the other hand, the inhibitory effect of the queen’s pheromones diminishes with distance. Maybe the level of egg removal also depends, like the inhibitory effect of the queen pheromones, on the distance from the queen. Indeed, further away from the queen the effect of the queen pheromone and the level of egg removal is reduced, making successful worker reproduction possible. In both subspecies, A. m. capensis and A. m. scutellata, egg removal behaviour is reduced further away from the queen. In the case of A. m. scutellata egg removal is lacking further away from the queen. This explains why colonies of scutellata are so prone to takeovers by laying Cape honeybee workers. One question in the context of parasitic Cape honeybees is how they manage to get into the host colony. One way could be that they get into the colonies during a natural colony merger which is common in African bees. Two unrelated colonies merged and it took them only 24 hours to show effective integration. Because both colonies are unrelated, the potential reproductive conflict among workers should be more strongly expressed than in a normal colony, which is not the result of a merger. Therefore, the effect of nestmate recognition for eggs on the egg removal behaviour was investigated. The results suggest that workers recognise the origin of an egg and that the standard policing experiments overestimate the level of egg removal and only represent relative values. Moreover, the results show that colony specific components on the eggs are more important than a postulated queen egg marking pheromone. Finally, for the first time empirical evidence from a population of the parasitic laying Cape honeybee workers, invading thousands of colonies of A. m. scutellata in northern South Africa, for a short-sighted selection theory is presented

Editorial : The effects of diet on health in insects

AUTHOR CONTRIBUTION : All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.Global change brings about a number of new challenges to insects. Urbanisation and landscape transformation, increasing temperatures, and frequent droughts will not only affect the species itself but also has knock-on effects throughout the trophic levels of a network. Plants might flower earlier and leave the previously default pollinator in a situation where it must look for a suitable alternative or starve. Long cold weather periods in spring after an early onset of flowering might starve both solitary and social insects in the beginning of the season. The increasing human food demand is resulting in agricultural intensification and an increase in monocultures, thereby reducing the diversity of floral nectar and pollen (1). Predatory and herbivore insects are similarly affected, with their favourite diet becoming desynchronised from their phenology, either temporally or spatially, due to changes in land use and the loss in connectivity linking favourable habitats.The National Research foundation of South Africa (NRF).https://www.frontiersin.org/journals/insect-scienceam2024Zoology and EntomologySDG-02:Zero HungerSDG-15:Life on lan

Differences in the suitability of published honey bee (Apis mellifera) reference genes between the African subspecies Apis mellifera scutellata and European derived Apis mellifera

DATA AVAILABILITY AND BENEFIT-SHARING STATEMENT : Data values (Cq & RNA amounts) are shared in Figures 1-3.Quantitative real-time polymerase chain reaction (qPCR) is a method widely used to determine changes and differences in gene expression. As target gene expression is most often quantified relative to the expression of reference genes, the validation of suitable reference genes is of critical importance. In practice, however, such validation might not be thoroughly conducted if the same species and the same tissue or body parts are used for qPCR experiments. Here we show, that qPCR reference genes published for workers of European honey bee (Apis mellifera) subspecies fail to be stably expressed in workers of the African subspecies Apis mellifera scutellata. This is the case even when the sampled workers are in the same life stage, the same organ was dissected and the same reagents were used. Thus, reference genes need to be thoroughly re-tested before they can be used as suitable references even when the only thing that changes is the subspecies used.Alexander von Humboldt-Stiftung and the National Research Foundation South Africa.http://www.wileyonlinelibrary.com/journal/mechj2024Zoology and EntomologyNon

Honeybees and nectar nicotine : deterrence and reduced survival versus potential health benefits

Secondary metabolites produced by plants for herbivore defence are often found in floral nectar, but their effect on the foraging behaviour and physiological performance of pollinators is largely unknown. Nicotine is highly toxic to most herbivores, and nicotine-based insecticides may contribute to current pollinator declines. We examined the effects of nectar nicotine on honeybee foraging choices and worker longevity. Free-flying honeybee (Apis mellifera scutellata) workers from six colonies were given a choice between multiple nicotine concentrations (0–1000 lM) in artificial nectar (0.15–0.63 M sucrose). The dose-dependent deterrent effect of nicotine was stronger in lower sugar concentrations, but even the highest nicotine concentrations did not completely repel honeybees, i.e. bees did not stop feeding on these diets. Nicotine in nectar acts as a partial repellent, which may keep pollinators moving between plants and enhance cross-pollination. In the second part of the study, newly emerged workers from 12 colonies were caged and fed one of four nicotine concentrations (0–300 lM) in 0.63 M sucrose for 21 days. Moderate (630 lM) nicotine concentrations had no significant detrimental effect, but high nicotine concentrations reduced the survival of caged workers and their nectar storage in the honey comb. In contrast, worker groups that survived poorly on sugar-only diets demonstrated increased survival on all nicotine diets. In the absence of alternative nectar sources, honeybees tolerate naturally occurring nectar nicotine concentrations; and low concentrations can even be beneficial to honeybees. However, high nicotine concentrations may have a detrimental effect on colony fitness.http://www.elsevier.com/ locate/ jinsphyshb2014ab201

Mandibular glands secrete 24-methylenecholesterol into honey bee (Apis mellifera) food jelly

DATA AVAILABILITY STATEMENT : The data that support the findings of this study (ng amounts of substances as evaluated by gas chromatography) are available in the methods and appendix of this article.Honey bee (Apis mellifera) workers feed their larvae with food jelly that is secreted by specialized glands in their heads – the hypopharyngeal and the mandibular glands. Food jelly contains all the nutrients the larvae need to develop into adult honey bees, including essential dietary sterols. The main sterol in food jelly, 24-methylenecholesterol (24MC), is pollen-derived and delivered in food jelly to the larvae in a complex with two proteins, major royal jelly protein 1 (MRJP1) and apisim. Whereas the proteins are synthesized in the hypopharyngeal glands, the sterol-secreting gland has not been identified. We here identified the mandibular glands as sterol-secreting gland for food jelly production by direct detection of the four main honey bee sterols (24MC, campesterol, β-sitosterol and isofucosterol). Furthermore, 24MC seems to be specifically enriched in the mandibular glands, thereby ensuring that food jelly contains the amounts of 24MC necessary for complex formation with MRJP1 and apisimin.https://www.elsevier.com/locate/ibmbam2024Zoology and EntomologySDG-15:Life on lan

Effects of cage volume and bee density on survival and nutrient intake of honeybees (Apis mellifera L.) under laboratory conditions

International audienceAbstractLaboratory experiments are vital to exploring the causes of pollinator loss, but for these experiments to be informative, they should attempt to replicate the hive environment and conserve social interactions. It is unclear how honeybee density and group size affect survival and behaviour in the laboratory. We manipulated cage volume (125–1312 ml) and honeybee group size (10–180 bees) and tested the effects on survival and feeding behaviour. Bees were allowed to regulate their intake from two liquid diets with dry ingredient protein: carbohydrate (P:C) ratios of 0:1 and 1:50 (w/w). Intake was consistent across cages, showing that feeding behaviour is largely unaffected by cage conditions. High survival was recorded in cages with a volume of 2.08 ml/bee, which falls within the natural range of 1.9–3.8 ml/bee in nest sites, and in groups of < 60 bees. We suggest that cage volume is more important than group size, and that cage dimensions should be adjusted so that each bee has < 3.0 ml of space

Physical properties of honeybee silk : a review

Honeybee silk is released from secretory cells and polymerises as birefringent tactoids in the lumen while silk is spun by a spinneret at the tip of the labium–hypopharynx and contains ά-helical proteins arranged in a four-strand coiled-coil structure. Wet fibres are only half as stiff as dried ones, but are equal in strength. The fibroin is hygroscopic and lithium thiocyanate and urea eliminate the yield point tested on both dry and wet fibres. The slopes of the solvent-related curves are reduced compared to those tested in water. Silk sheets are independent of temperature when deformed in tension. This fibre is rather crystalline and its hydration sensitivity, expressed as the ratio of the elastic modulus of wet to that of dry fibre, is 0.53. The ά-helical fibroins are predicted to have an antiparallel tetrameric configuration that is shown as a possible structural model. The molecular structure of ά-helical proteins maximizes their robustness with minimal use of building materials. In conclusion, it appears that the composition, molecular topology and amino acid content and sequence are a highly conserved feature in the evolution of silk in Apis species.http://link.springer.com/journal/13592hb201

The influence of sublethal neonicotinoid doses on individual Apis mellifera scutellata thermotolerance

DATA AVAILABILITY : Data will be made available on Research Gate.Honey bee (Apis mellifera L.) thermoregulation plays an integral part in their behaviour and physiology and has been shown to be vulnerable to the effects of neonicotinoid insecticides. Baseline thermotolerance of 53.8 °C (defined as LT50; temperature at which 50% mortality is recorded) was determined for this subspecies. We evaluated the influence of sublethal dosages of three widely used neonicotinoid insecticides, clothianidin, imidacloprid and thiamethoxam, on individual Apis mellifera scutellata thermotolerance, each evaluated at a range of increasing ambient temperatures. For all three neonicotinoid treatments, A. m. scutellata thermotolerance was decreased by more than 3 °C as compared to the baseline data. Such a reduction in honey bee thermotolerance, especially under the increasing frequency and intensity of hot weather events, is a cause for concern when considering legislation and use of these neonicotinoids in the South African agricultural and suburban setting.The South African National Research Foundation (NRF) and the University of Pretoria.https://link.springer.com/journal/13592hj2024Zoology and EntomologySDG-13:Climate actionSDG-15:Life on lan

A new design for honey bee hoarding cages for laboratory experiments

Honey bees are the subject of research around the world due to their great economic importance and current population declines (vanEngelsdorp and Meixner, 2010). Many studies cannot be conducted at the colony level. Controlled cage experiments provide insight into behavioural interactions (Elzen et al., 2001), diseases (Martín-Hernández et al., 2009), nutritional requirements (Altaye et al., 2010) and effects of insecticides and genetically engineered plants on these important pollinators (Malone et al., 1999; Medrzycki et al., 2003).A grant from BBSRC, Defra, NERC, the Scottish Government and the Wellcome Trust, under the Insect Pollinators Initiative (BBI000968/1)http://www.ibra.org.uk/am2014ab201