An official website of the United States government
In temperate climates, honey bees show strong phenotypic plasticity associated with seasonal changes. In summer, worker bees typically only survive for about a month and can be further classified as young nurse bees (which feed the developing brood) and older forager bees. In winter, brood production and foraging halts and the worker bees live several months. These differences in task and longevity are reflected in their physiology, with summer nurses and long-lived winter bees typically having larger fat bodies, high expression levels of vitellogenin (a longevity, nutrition, and immune-related gene), and larger provisioning glands in their head. The environmental factors (both within the colony and within the surrounding environment) that trigger this transition to long-lived winter bees are poorly understood. One theory suggests is that winter bees are an extended nurse bee state, brought on by a reduction in nursing duties in the fall (i.e., lower brood area). We examine that theory here by assessing nurse bee physiology in both the summer and fall, in colonies with varying levels of brood. We find that season is a better predictor of nurse bee physiology than brood area. This finding suggests that seasonal factors beyond brood area, such as pollen availability and colony demography, may be necessary for inducing the winter bee phenotype. This finding furthers our understanding of winter bee biology, which could have important implications for colony management for winter, a critical period for colony survival.
more »
« less
Carbohydrate nutrition associated with health of overwintering honey bees
Abstract In temperate climates, honey bees rely on stored carbohydrates to sustain them throughout the winter. In nature, honey serves as the bees’ source of carbohydrates, but when managed, beekeepers often harvest honey and replace it with cheaper, artificial feed. The effects of alternative carbohydrate sources on colony survival, strength, and individual bee metabolic health are poorly understood. We assessed the impacts of carbohydrate diets (honey, sucrose syrup, high-fructose corn syrup, and invert syrup) on colony winter survival, population size, and worker bee nutritional state (i.e., fat content and gene expression of overwintered bees and emerging callow bees). We observed a nonsignificant trend for greater survival and larger adult population size among colonies overwintered on honey compared to the artificial feeds, with colonies fed high-fructose corn syrup performing particularly poorly. These trends were mirrored in individual bee physiology, with bees from colonies fed honey having significantly larger fat bodies than those from colonies fed high-fructose corn syrup. For bees fed honey or sucrose, we also observed gene expression profiles consistent with a higher nutritional state, associated with physiologically younger individuals. That is, there was significantly higher expression of vitellogenin and insulin-like peptide 2 and lower expression of insulin-like peptide 1 and juvenile hormone acid methyltransferase in the brains of bees that consumed honey or sucrose syrup relative to those that consumed invert syrup or high-fructose corn syrup. These findings further our understanding of the physiological implications of carbohydrate nutrition in honey bees and have applied implications for colony management.
more »
« less
- Award ID(s):
- 2109109
- PAR ID:
- 10478369
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Insect Science
- Volume:
- 23
- Issue:
- 6
- ISSN:
- 1536-2442
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Over the last quarter century, increasing honey bee colony losses motivated standardized large-scale surveys of managed honey bees (Apis mellifera), particularly in Europe and the United States. Here we present the first large-scale standardized survey of colony losses of managed honey bees and stingless bees across Latin America. Overall, 1736 beekeepers and 165 meliponiculturists participated in the 2-year survey (2016–2017 and 2017–2018). On average, 30.4% of honey bee colonies and 39.6% of stingless bee colonies were lost per year across the region. Summer losses were higher than winter losses in stingless bees (30.9% and 22.2%, respectively) but not in honey bees (18.8% and 20.6%, respectively). Colony loss increased with operation size during the summer in both honey bees and stingless bees and decreased with operation size during the winter in stingless bees. Furthermore, losses differed significantly between countries and across years for both beekeepers and meliponiculturists. Overall, winter losses of honey bee colonies in Latin America (20.6%) position this region between Europe (12.5%) and the United States (40.4%). These results highlight the magnitude of bee colony losses occurring in the region and suggest difficulties in maintaining overall colony health and economic survival for beekeepers and meliponiculturists.more » « less
-
Foster, Leonard (Ed.)Abstract Honey bees are important organisms for research in many fields, including physiology, behavior, and ecology. Honey bee colonies are relatively easy and affordable to procure, manage, and replace. However, some difficulties still exist in honey bee research, specifically that honey bee colonies have a distinct seasonality, especially in temperate regions. Honey bee colonies transition from a large society in which workers have a strict temporal division of labor in the summer, to a group of behaviorally flexible workers who manage the colony over winter. Furthermore, opening colonies or collecting bees when they are outside has the potential to harm the colony because of the disruption in thermoregulation. Here, we present a simple and affordable indoor management method utilizing a mylar tent and controlled environmental conditions that allows bees to freely fly without access to outdoor space. This technique permits research labs to successfully keep several colonies persistently active during winter at higher latitudes. Having an extended research period is particularly important for training students, allowing preliminary experiments to be performed, and developing methods. However, we find distinct behavioral differences in honey bees managed in this situation. Specifically learning and thermoregulatory behaviors were diminished in the bees managed in the tent. Therefore, we recommend caution in utilizing these winter bees for full experiments until more is known. Overall, this method expands the research potential on honey bees, and calls attention to the additional research that is needed to understand how indoor management might affect honey bees.more » « less
-
In holometabolous insects, larval nutrition affects adult body size, a life history trait with a profound influence on performance and fitness. Individual nutritional components of larval diets are often complex and may interact with one another, necessitating the use of a geometric framework for elucidating nutritional effects. In the honey bee, Apis mellifera, nurse bees provision food to developing larvae, directly moderating growth rates and caste development. However, the eusocial nature of honey bees makes nutritional studies challenging, because diet components cannot be systematically manipulated in the hive. Using in vitro rearing, we investigated the roles and interactions between carbohydrate and protein content on larval survival, growth, and development in A. mellifera. We applied a geometric framework to determine how these two nutritional components interact across nine artificial diets. Honey bees successfully completed larval development under a wide range of protein and carbohydrate contents, with the medium protein (∼5%) diet having the highest survival. Protein and carbohydrate both had significant and non-linear effects on growth rate, with the highest growth rates observed on a medium-protein, low-carbohydrate diet. Diet composition did not have a statistically significant effect on development time. These results confirm previous findings that protein and carbohydrate content affect the growth of A. mellifera larvae. However, this study identified an interaction between carbohydrate and protein content that indicates a low-protein, high-carb diet has a negative effect on larval growth and survival. These results imply that worker recruitment in the hive would decline under low protein conditions, even when nectar abundance or honey stores are sufficient.more » « less
-
Abstract Varroa destructor is an ectoparasitic mite of immature and adult honey bees that can transmit several single-stranded RNA viruses to its host. Varroa reproduce in brood cells, and mite populations increase as colonies produce brood in spring and summer. Mite numbers also can sharply rise, particularly in the fall, by the migration of varroa into hives on foragers. Colonies with high levels of varroa and viruses often die over the winter. Feeding colonies pollen might keep virus levels low and improve survival because of the positive effects of pollen on immunity and colony growth. We compared varroa and virus levels and overwinter survival in colonies with (fed) and without (unfed) supplemental pollen. We also measured the frequency of capturing foragers with mites (FWM) at colony entrances to determine its relationship to varroa and virus levels. Colonies fed supplemental pollen were larger than unfed colonies and survived longer. Varroa populations and levels of Deformed wing virus (DWV) rose throughout the season, and were similar between fed and unfed colonies. The growth of varroa populations was correlated with FWM in fed and unfed colonies, and significantly affected DWV levels. Increasing frequencies of FWM and the effects on varroa populations might reduce the positive influence of supplemental pollen on immune function. However, pollen feeding can stimulate colony growth and this can improve colony survival.more » « less
