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

Stress response in honeybees is associated with changes in task-related physiology and energetic metabolism

In a rapidly changing environment, honeybee colonies are increasingly exposed to diverse sources of stress (e.g., new parasites, pesticides, climate warming), which represent a challenge to individual and social homeostasis. However, bee physiological responses to stress remain poorly understood. We therefore exposed bees specialised in different tasks (nurses, guards and foragers) to ancient (immune and heat stress) or historically more recent sources of stress (pesticides), and we determined changes in the expression of genes linked to behavioural maturation (vitellogenin – vg and juvenile hormone esterase – jhe) as well as in energetic metabolism (glycogen level, expression level of the receptor to the adipokinetic hormone – akhr, and endothermic performance). While acute exposure to sublethal doses of two pesticides did not affect vg and jhe expression, immune and heat challenges caused a decrease and increase in both genes, respectively, suggesting that bees had responded to ecologically relevant stressors. Since vg and jhe are expressed to a higher level in nurses than in foragers, it is reasonable to assume that an immune challenge stimulated behavioural maturation to decrease potential contamination risk and that a heat challenge promoted a nurse profile for brood thermoregulation. All behavioural castes responded in the same way. Though endothermic performances did not change upon stress exposure, the akhr level dropped in immune and heat-challenged individuals. Similarly, the abdomen glycogen level tended to decline in immune-challenged bees. Altogether, these results suggest that bee responses are stress specific and adaptive but that they tend to entail a reduction of energetic metabolism that needs to be studied on a longer timescale

Between day comparison of spatial association (≤1 m).

<p>Sociograms comparing A) non-testing conditions and B) testing conditions. Nodes represent individuals in the group (n = 5), node shape indicates sex (square, male), node size and opacity represents centrality, edges represent dyadic association (rates of and edge thickness represents rates of association. Positions of nodes determined through MDS analysis. Numbers represent position in the hierarchy.</p

Rates of group behaviours per hour.

<p>Values are Mean±SD, N<i> = </i>5.</p

Description of sampling conditions and contexts, including total observational time.

<p>Description of sampling conditions and contexts, including total observational time.</p

Within day comparisons of spatial association.

<p>Sociograms comparing A) post-testing condition, B) during the testing of individual Bai, C) during the testing of individual Dru and D) during the testing of individual Sat. See Fig. 1 for details. The individual who split from the group to participate in cognitive testing is not included in the social networks B, C, and D.</p

List of behaviours monitored during all conditions.

<p>FS = recorded during focal samples, SS = recorded during scan samples.</p

Within day comparison of aggressive interaction.

<p>Sociograms comparing A) non-testing conditions and B) testing conditions. See Fig. 1 for details. Instead here, node size and opacity represents in-degree centrality (received aggression) and edges and arrows represent the directed aggressive interaction and edge thickness represents rates of interaction.</p

Chemical detection triggers honey bee defense against a destructive parasitic threat

International audienceInvasive species events related to globalization are increasing, resulting in parasitic outbreaks. Understanding of host defense mechanisms is needed to predict and mitigate against the consequences of parasite invasion. Using the honey bee Apis mellifera and the mite Varroa destructor, as a host–parasite model, we provide a comprehensive study of a mechanism of parasite detection that triggers a behavioral defense associated with social immunity. Six Varroa-parasitization-specific (VPS) compounds are identified that trigger Varroa-sensitive hygiene (VSH, bees’ key defense against Varroa sp.), enable the selective recognition of a parasitized brood and induce responses that mimic intrinsic VSH activity in bee colonies. We also show that individuals engaged in VSH exhibit a unique ability to discriminate VPS compounds from healthy brood signals. These findings enhance our understanding of a critical mechanism of host defense against parasites, and have the potential to apply the integration of pest management in the beekeeping sector

The impact of cognitive testing on the welfare of group housed primates

Providing cognitive challenges to zoo-housed animals may provide enriching effects and subsequently enhance their welfare. Primates may benefit most from such challenges as they often face complex problems in their natural environment and can be observed to seek problem solving opportunities in captivity. However, the extent to which welfare benefits can be achieved through programmes developed primarily for cognitive research is unknown. We tested the impact of voluntary participation cognitive testing on the welfare of a socially housed group of crested macaques (Macaca nigra) at the Macaque Study Centre (Marwell Zoo). First, we compared the rate of self-directed and social behaviours on testing and non-testing days, and between conditions within testing days. Minimal differences in behaviour were found when comparing testing and non-testing days, suggesting that there was no negative impact on welfare as a result of cognitive testing. Lipsmacking behaviours were found to increase and aggressive interaction was found to decrease in the group as a result of testing. Second, social network analysis was used to assess the effect of testing on associations and interactions between individuals. The social networks showed that testing subjects increased their association with others during testing days. One interpretation of this finding could be that providing socially housed primates with an opportunity for individuals to separate from the group for short periods could help mimic natural patterns of sub-group formation and reunion in captivity. The findings suggest, therefore, that the welfare of captive primates can be improved through the use of cognitive testing in zoo environments