Skip to main content
European Commission logo print header

How does dopamine link QMP with reproductive repression to mediate colony harmony and productivity in the honeybee?

Periodic Reporting for period 1 - DRiveR (How does dopamine link QMP with reproductive repression to mediate colony harmony and productivity in the honeybee?)

Periodo di rendicontazione: 2018-03-01 al 2020-02-29

The honeybee is the most important managed pollinator species globally. Honeybees are extremely efficient pollinators, at least in part because of their unusual life-history. Honeybees live in large colonies and each colony has only one reproductive female, the other bees are also all females – but are kept from reproducing by the presence of a queen and her pheromone (Queen Mandibular Pheromone, QMP). This reproductive division of labour is integral to the success of honeybee colonies and crucial for ensuring food-security through maintaining pollinator capacity. Yet we don’t really have a good understanding of how QMP represses reproduction in honeybee workers, nor the role of this repression in maximising colony productivity.
This project aimed to determine whether dopamine (a biogenic amine) links the brain and ovary with exposure to QMP in the honeybee. This project also sought to determine whether environmental perturbations, such as exposure to pesticides disrupts this signalling leading to a problem in a honeybee colony and possibly contributing to colony declines.
The objectives of this project were to determine how dopamine links the brain and ovary in the worker honeybee mediating responsiveness to QMP and define what role this pathway has in maintaining colony harmony and maximising colony productivity. To achieve this the project proposed three specific objectives; 1. How does dopamine link reproduction with QMP in the worker honeybee? 2. Is dopamine signalling responsible for establishing individual variation response to QMP 3. Is dopamine-signalling integral for colony productivity and is it resilient to environmental perturbation?
The overall objective of this project was to determine how dopamine links the brain and ovary in the worker honeybee mediating responsiveness to QMP and to define what role this pathway has in maintaining colony harmony and maximising colony productivity.

The majority of our focus in this project has been attempting to link dopamine signalling in the brain and ovary with QMP. We have shown that multiple tissues in the bee produce dopamine, including both the brain and the ovary. This raises the possibility that dopamine acts very differently in the honeybee to other insect species. Understanding this basic biology in the honeybee, such as how dopamine signalling differs from other insects is really important as it may, in the future, help us protect this really important pollinator species.

In our project we have also shown that dopamine signalling is likely directly affected by QMP; exposure to QMP affects both the levels of dopamine that we detect in various honeybee tissues but also the levels of dopamine receptors expression and we also see differences in expression of genes that we know are responsive to dopamine. This, altogether, is consistent with dopamine signalling being a key mechanism by which QMP represses reproduction. To test this hypothesis directly we were able to manipulate dopamine levels either by feeding microcolonies of bees an inhibitor of dopamine production or by stimulating dopamine production. The results from these manipulations indicate that that the relationship between dopamine signalling and QMP isn’t as simple as we had first thought and we are planning more experiments to get to the bottom of the mechanisms by which QMP affects dopamine signalling and mediates repression of reproduction in honeybee workers.

In this project, we have also used state-of-the-art approaches to determine the primary response of honeybee workers to the loss of the queen. Finding out how the bee, in particular the ovary, is affected by the loss of the queen pheromone immediately and preceding any physiological change tells us about the primary response of the ovary and is a major step-change in our thinking about how the ovary is responding to QMP and the role of dopamine in this process.

We are currently completing experiments to determine whether dopamine signalling is perturbed when bees are exposed to common environmental contaminants such as pesticides.

This project has resulted in three publications, eight conference presentations, and there are another six publications planned.
One of the main findings of this project is the determination that QMP likely does act through dopamine signalling to stop workers from reproducing, but that the physiological effect of dopamine is dependent on the dose – this indicates that dopamine signalling is more complicated than we expected and may be functioning differently in the honeybee as compared with other insect species. We are currently collecting more data to complete the objectives in this grant but also to address specific questions raised in this grant. This project will, therefore, give significant insights into honeybee physiology and behaviour. Understanding this aspect honeybee biology is important as the honeybee is a critically important pollinator species. In performing pollination, the honeybee is potentially exposed to numerous environmental chemicals including pesticides which have been shown to have sub-lethal effects on honeybees. Our data indicate that this may be partially through impacting on dopamine signalling. This has the potential to have significant impacts on agrichemical usage including pesticides, but also potentially for informing targets for the development of pesticides in the future.

Honeybees are eusocial species, meaning that one female, the queen, is responsible for the majority of the reproduction. This seemingly goes against Darwin’s theory of evolution by natural selection where all individuals should want to reproduce, to pass their genes on to the next generation. Although we have a good understanding of the evolutionary theory of how this remarkable life-history strategy evolves, we don’t really understand how such major shifts in evolution occur. My work, and that of others in this field, will help inform our understanding of these crucial evolutionary processes. Insight into evolutionary processes is not just important from an academic standpoint, but may help us understand how species that exist today may adapt or evolve in response to changing environments.
Apis mellifera foraging