New insights into honey bee (Apis mellifera) pheromone communication. Is the queen mandibular pheromone alone in colony regulation?

<p>Abstract</p> <p>Background</p> <p>In social insects, the queen is essential to the functioning and homeostasis of the colony. This influence has been demonstrated to be mediated through pheromone communication. However, the only social insect for which any queen pheromone has been identified is the honey bee (<it>Apis mellifera</it>) with its well-known queen mandibular pheromone (QMP). Although pleiotropic effects on colony regulation are accredited to the QMP, this pheromone does not trigger the full behavioral and physiological response observed in the presence of the queen, suggesting the presence of additional compounds. We tested the hypothesis of a pheromone redundancy in honey bee queens by comparing the influence of queens with and without mandibular glands on worker behavior and physiology.</p> <p>Results</p> <p>Demandibulated queens had no detectable (E)-9-oxodec-2-enoic acid (9-ODA), the major compound in QMP, yet they controlled worker behavior (cell construction and queen retinue) and physiology (ovary inhibition) as efficiently as intact queens.</p> <p>Conclusions</p> <p>We demonstrated that the queen uses other pheromones as powerful as QMP to control the colony. It follows that queens appear to have multiple active compounds with similar functions in the colony (pheromone redundancy). Our findings support two hypotheses in the biology of social insects: (1) that multiple semiochemicals with synonymous meaning exist in the honey bee, (2) that this extensive semiochemical vocabulary exists because it confers an evolutionary advantage to the colony.</p

Brood thermoregulation effectiveness is positively linked to the amount of brood but not to the number of bees in honeybee colonies

To ensure the optimal development of brood, a honeybee colony needs to regulate its temperature within a certain range of values (thermoregulation), regardless of environmental changes in biotic and abiotic factors. While the set of behavioural and physiological responses implemented by honeybees to regulate the brood temperature has been well studied, less is known about the factors that may influence the effectiveness of this thermoregulation. Based on the response threshold model of task allocation, increased effectiveness of colony homeostasis should be driven by increases in group size. Therefore, we determined whether colony size (number of adult bees and amount of brood) positively influenced the effectiveness of brood thermoregulation that we measured via two criteria: (i) the brood temperature accuracy, via mean brood temperature, supposedly close to the optimum value for brood rearing, and (ii) the stability of the temperature around the mean value. Finally, within the applied perspective of honeybee colony monitoring, we assessed whether the effectiveness of thermoregulation could be used as a proxy of colony size. For that purpose, we followed 29 honeybee colonies over two years, measured both brood and adult population size regularly over the beekeeping season, and monitored the brood temperature over the 24 hours preceding the inspections of these colonies. We then studied the effect of the size of the colony (number of adult bees and number of brood cells), as well as meteorological variables, on the effectiveness of thermoregulation (mean and stability of brood temperature). We found a clear link between meteorological conditions and brood thermoregulation (mean temperature and its stability). Interestingly, mean brood temperature was also positively linked to the amount of brood, while its stability did not seem influenced by the size of the colony (number of bees or brood amount). The relationship between brood amount and mean temperature was however too weak for clearly discriminating colony population size based solely on the brood thermoregulatory effectiveness. These results demonstrate an extremely high effectiveness of honeybee colonies to thermoregulate the brood regardless of colony size

Honeybee Colony Vibrational Measurements to Highlight the Brood Cycle

Insect pollination is of great importance to crop production worldwide and honey bees are amongst its chief facilitators. Because of the decline of managed colonies, the use of sensor technology is growing in popularity and it is of interest to develop new methods which can more accurately and less invasively assess honey bee colony status. Our approach is to use accelerometers to measure vibrations in order to provide information on colony activity and development. The accelerometers provide amplitude and frequency information which is recorded every three minutes and analysed for night time only. Vibrational data were validated by comparison to visual inspection data, particularly the brood development. We show a strong correlation between vibrational amplitude data and the brood cycle in the vicinity of the sensor. We have further explored the minimum data that is required, when frequency information is also included, to accurately predict the current point in the brood cycle. Such a technique should enable beekeepers to reduce the frequency with which visual inspections are required, reducing the stress this places on the colony and saving the beekeeper time

E-β-Ocimene, a Volatile Brood Pheromone Involved in Social Regulation in the Honey Bee Colony (Apis mellifera)

Background: In honey bee colony, the brood is able to manipulate and chemically control the workers in order to sustain their own development. A brood ester pheromone produced primarily by old larvae (4 and 5 days old larvae) was first identified as acting as a contact pheromone with specific effects on nurses in the colony. More recently a new volatile brood pheromone has been identified: E-β-ocimene, which partially inhibits ovary development in workers. [br/] Methodology and Principal Finding: Our analysis of E-β-ocimene production revealed that young brood (newly hatched to 3 days old) produce the highest quantity of E-b-ocimene relative to their body weight. By testing the potential action of this molecule as a non-specific larval signal, due to its high volatility in the colony, we demonstrated that in the presence of E-β-ocimene nest workers start to forage earlier in life, as seen in the presence of real brood. [br/] Conclusions/Significance: In this way, young larvae are able to assign precedence to the task of foraging by workers in order to increase food stores for their own development. Thus, in the complexity of honey bee chemical communication, E-β- ocimene, a pheromone of young larvae, provides the brood with the means to express their nutritional needs to the workers

Host adaptations reduce the reproductive success of Varroa destructor in two distinct European honey bee populations

Honey bee societies (Apis mellifera), the ectoparasitic mite Varroa destructor, and honey bee viruses that are vectored by the mite, form a complex system of host–parasite interactions. Coevolution by natural selection in this system has been hindered for European honey bee hosts since apicultural practices remove the mite and consequently the selective pressures required for such a process. An increasing mite population means increasing transmission opportunities for viruses that can quickly develop into severe infections, killing a bee colony. Remarkably, a few subpopulations in Europe have survived mite infestation for extended periods of over 10 years without management by beekeepers and offer the possibility to study their natural host–parasite coevolution. Our study shows that two of these “natural” honey bee populations, in Avignon, France and Gotland, Sweden, have in fact evolved resistant traits that reduce the fitness of the mite (measured as the reproductive success), thereby reducing the parasitic load within the colony to evade the development of overt viral infections. Mite reproductive success was reduced by about 30% in both populations. Detailed examinations of mite reproductive parameters suggest these geographically and genetically distinct populations favor different mechanisms of resistance, even though they have experienced similar selection pressures of mite infestation. Compared to unrelated control colonies in the same location, mites in the Avignon population had high levels of infertility while in Gotland there was a higher proportions of mites that delayed initiation of egg-laying. Possible explanations for the observed rapid coevolution are discussed

Essai d’efficacité thérapeutique de l’amitraze contre Varroa destructor

De nombreux exemples montrent qu’à terme les acariens deviennent résistants aux acaricides utilisés pour contrôler leurs populations. L’amitraze est utilisée depuis plus de 23 ans pour lutter contre le varroa et il se pose régulièrement la question de l’apparition de populations résistantes. Cet article traite de l’efficacité de cette molécule sur des populations de varroas en Avignon

Should I stay or should I go: honeybee drifting behaviour as a function of parasitism

Nest drifting is often observed in honeybees (Apis mellifera ) and can be detrimental to neighbouring colonies because it has the potential to increase disease transmission. However, the characteristics of drifting behaviour over a honeybee’s lifetime and the influence of parasitism on this phenomenon have been insufficiently investigated. Using optical bee counters, we tracked the drifting behaviour of workers that were either infected with the parasite Nosema ceranae or uninfected. Approximately 10 % of the tracked bees drifted into a foreign colony. The drifting prevalencewas influenced by the colony’s location in space but not by N. ceranae parasitism. However, the number and duration of drifts changed over the lifetime of the bees and the season, and parasitism had an effect on drifters, with Nosema -infected bees performing more but shorter drifts. This phenomenon was more pronounced in old bees (+62 and −15%for the number and duration of drifts, respectively) and could potentially be explained by the energetic stress induced by the parasite. In conclusion, combining a detailed analysis of drifting behaviour with the actual risk of newly established disease in colonies will benefit our knowledge of bee epidemiology

Flight activity of honey bee (Apis mellifera) drones

Compared to the queen or the workers, the biology of honey bee Apis mellifera L. drones is poorly known. Available information on drone activity is based mainly on direct observations during a limited period of time and for a restricted time of the day. Complete registers of the flight activity of honey bee drones are lacking. We studied the activity of A. mellifera drones during their entire life in spring and summer by using an optical bee counter at the entrance of the hive. Drones were active in the afternoon, with most flights occurring between 14:00 and 18:00. Short orientation flights were performed at 6–9 days old, and longer mating flights of 30 min were performed from the age of 21 days onward during the spring and from the age of 13 days onward during the summer. Our registers show that 50 and 80% of the drones remained faithful to their colony (did not drift) in spring and summer, respectively. The present study confirms existing information, but also reveals unknown aspects about drone biology