Monoterpenoid-based preparations in beehives affect learning, memory, and gene expression in the bee brain

Combined effect of a neonicotinoid insecticide and a fungicide on honeybee gut epithelium and microbiota, adult survival, colony strength and foraging preferences

Fungicides, insecticides and herbicides are widely used in agriculture to counteract pathogens and pests. Several of these molecules are toxic to non-target organisms such as pollinators and their lethal dose can be lowered if applied as a mixture. They can cause large and unpredictable problems, spanning from behavioural changes to alterations in the gut. The present work aimed at understanding the synergistic effects on honeybees of a combined in-hive exposure to sub-lethal doses of the insecticide thiacloprid and the fungicide penconazole. A multidisciplinary approach was used: honeybee mortality upon exposure was initially tested in cage, and the colonies development monitored. Morphological and ultrastructural analyses via light and transmission electron microscopy were carried out on the gut of larvae and forager honeybees. Moreover, the main pollen foraging sources and the fungal gut microbiota were studied using Next Generation Sequencing; the gut core bacterial taxa were quantified via qPCR. The mortality test showed a negative effect on honeybee survival when exposed to agrochemicals and their mixture in cage but not confirmed at colony level. Microscopy analyses on the gut epithelium indicated no appreciable morphological changes in larvae, newly emerged and forager honeybees exposed in field to the agrochemicals. Nevertheless, the gut microbial profile showed a reduction of Bombilactobacillus and an increase of Lactobacillus and total fungi upon mixture application. Finally, we highlighted for the first time a significant honeybee diet change after pesticide exposure: penconazole, alone or in mixture, significantly altered the pollen foraging preference, with honeybees preferring Hedera pollen. Overall, our in-hive results showed no severe effects upon administration of sublethal doses of thiacloprid and penconazole but indicate a change in honeybees foraging preference. A possible explanation can be that the different nutritional profile of the pollen may offer better recovery chances to honeybees.

Pollen diet mediates how pesticide exposure impacts brain gene expression in nest-founding bumble bee queens

A primary goal in biology is to understand the effects of multiple, interacting environmental stressors on organisms. Wild and domesticated bees are exposed to a wide variety of interacting biotic and abiotic stressors, with widespread declines in floral resources and agrochemical exposure being two of the most important. In this study, we used examinations of brain gene expression to explore the sublethal consequences of neonicotinoid pesticide exposure and pollen diet composition in nest-founding bumble bee queens. We demonstrate for the first time that pollen diet composition can influence the strength of bumble bee queen responses to pesticide exposure at the molecular level. Specifically, one pollen mixture in our study appeared to buffer bumble bee queens entirely against the effects of pesticide exposure, with respect to brain gene expression. Additionally, we detected unique effects of pollen diet and sustained (versus more temporary) pesticide exposure on queen gene expression. Our findings support the hypothesis that nutritional status can help buffer animals against the harmful effects of other stressors, including pesticides, and highlight the importance of using molecular approaches to explore sublethal consequences of stressors.

The Effect of Eucalyptol on Nursing Home Residents

Eucalyptol is one of the most popular volatile components. It is used in many essential oils for relieving sinus and lung congestion caused by a variety of conditions. This pilot study sought to analyze clinical evidence for the effect of the scent of eucalyptol on the cognitive function of elderly people. Seventy nursing-home residents with cognitive impairment were recruited. Three one-week experiments were performed: eucalyptol scent was diffused in bedrooms with a diffuser only at wake-up time in the first experiment, and at wake-up time and bedtime in the second and third experiments. Results showed that although an improvement was not seen when using Mini Mental State Examination (MMSE) and Cohen-Mansfild Agitation Inventory (CMAI) measures, Dementia Behavior Disturbance Scale (DBD) scores improved significantly, even though no subject reported perceiving the scent. The significant improvements of the behaviour were found not only among the subjects whose room had a diffuser but also among the subjects who were exposed to an unperceivable level of eucalyptol drifted in the living room.

Impact of Stressors on Honey Bees (Apis mellifera; Hymenoptera: Apidae): Some Guidance for Research Emerge from a Meta-Analysis

Bees play an essential role in plant pollination and their decline is a threat to crop yields and biodiversity sustainability. The causes of their decline have not yet been fully identified, despite the numerous studies that have been carried out, especially on Apis mellifera. This meta-analysis was conducted to identify gaps in the current research and new potential directions for research. The aim of this analysis of 293 international scientific papers was to achieve an inventory of the studied populations, the stressors and the methods used to study their impact on Apis mellifera. It also aimed to investigate the stressors with the greatest impact on bees and explore whether the evidence for an impact varies according to the type of study or the scale of study. According to this analysis, it is important to identify the populations and the critical developmental stages most at risk, and to determine the differences in stress sensibility between subspecies. This meta-analysis also showed that studies on climate change or habitat fragmentation were lacking. Moreover, it highlighted that technical difficulties in the field and the buffer effect of the colony represent methodological and biological barriers that are still difficult to overcome. Mathematical modeling or radio frequency identification (RFID) chips represent promising ways to overcome current methodological difficulties.

Identification of the neurotransmitter profile of AmFoxP expressing neurons in the honeybee brain using double-label in situ hybridization

BACKGROUND

FoxP transcription factors play crucial roles for the development and function of vertebrate brains. In humans the neurally expressed FOXPs, FOXP1, FOXP2, and FOXP4 are implicated in cognition, including language. Neural FoxP expression is specific to particular brain regions but FoxP1, FoxP2 and FoxP4 are not limited to a particular neuron or neurotransmitter type. Motor- or sensory activity can regulate FoxP2 expression, e.g. in the striatal nucleus Area X of songbirds and in the auditory thalamus of mice. The DNA-binding domain of FoxP proteins is highly conserved within metazoa, raising the possibility that cellular functions were preserved across deep evolutionary time. We have previously shown in bee brains that FoxP is expressed in eleven specific neuron populations, seven tightly packed clusters and four loosely arranged groups.

RESULTS

The present study examined the co-expression of honeybee FoxP (AmFoxP) with markers for glutamatergic, GABAergic, cholinergic and monoaminergic transmission. We found that AmFoxP could co-occur with any one of those markers. Interestingly, AmFoxP clusters and AmFoxP groups differed with respect to homogeneity of marker co-expression; within a cluster, all neurons co-expressed the same neurotransmitter marker, within a group co-expression varied. We also assessed qualitatively whether age or housing conditions providing different sensory and motor experiences affected the AmFoxP neuron populations, but found no differences.

CONCLUSIONS

Based on the neurotransmitter homogeneity we conclude that AmFoxP neurons within the clusters might have a common projection and function whereas the AmFoxP groups are more diverse and could be further sub-divided. The obtained information about the neurotransmitters co-expressed in the AmFoxP neuron populations facilitated the search of similar neurons described in the literature. These comparisons revealed e.g. a possible function of AmFoxP neurons in the central complex. Our findings provide opportunities to focus future functional studies on invertebrate FoxP expressing neurons. In a broader context, our data will contribute to the ongoing efforts to discern in which cases relationships between molecular and phenotypic signatures are linked evolutionary.