Periodic Reporting for period 3 - ElectroBee (Mechanisms of electroreception in bees and other terrestrial animals)
Période du rapport: 2020-09-01 au 2022-02-28
The project aims at generating transformative information on the sense of electroreception in terrestrial arthropods. The project will identify the how and why of electroreception in honeybees and bumblebees, and establish the importance of this new sense in the sensory ecology of these animals. Beyond bees, the project is investigating aerial electroreception in other arthropod species, namely beetles, treehoppers and spiders.
The importance of this project resides in the fact that aerial electroreception, as a new sense, might be more general present in animals than previously surmised. Our work has established that electroreception is possible outside the aquatic environment, where it has been scientifically studied for more than half a century. The overall objective is to develop a general framework in which a sound and testable scientific rationale that explains electroreception in air.
The project will contribute to evaluating whether the electric ecology of natural environments is affected or not by human activity. The world, under human influence, has become very electrically-laden, and this change may generate alterations in the physical and sensory ecologies of organisms, including humans. Studying an evolved sense, and describing and characterising it in its natural condition will help appreciate the changes and potential disruption, or their absence, for the health of ecosystems and their organisms. An additional overall objective is to delineate, using said framework, predict and evaluate the conditions presiding to electroreception in air, and to develop a reliable logic and tools to measure anthropogenic deviations or alterations of it.
The importance of this project resides in the fact that aerial electroreception, as a new sense, might be more general present in animals than previously surmised. Our work has established that electroreception is possible outside the aquatic environment, where it has been scientifically studied for more than half a century. The overall objective is to develop a general framework in which a sound and testable scientific rationale that explains electroreception in air.
The project will contribute to evaluating whether the electric ecology of natural environments is affected or not by human activity. The world, under human influence, has become very electrically-laden, and this change may generate alterations in the physical and sensory ecologies of organisms, including humans. Studying an evolved sense, and describing and characterising it in its natural condition will help appreciate the changes and potential disruption, or their absence, for the health of ecosystems and their organisms. An additional overall objective is to delineate, using said framework, predict and evaluate the conditions presiding to electroreception in air, and to develop a reliable logic and tools to measure anthropogenic deviations or alterations of it.
We have initiated work on several work packages. In particular, the part dedicated to further instrumentation development has yielded some valuable outcomes. For example, we have been able to break a length scale barrier with a new laser Doppler vibrometer, allowing us to measure electromechanical actuation with unprecedented spatial accuracy. Using our state of the art low-noise laboratories at the University of Bristol (Robert lab), the resolution obtained in the magnitude of vibration is ground-breaking. We have been able to measure deflection of bulk sensory insect material as low as 8 picometres. To facilitate perspective, it might be noted that 10 pico metres are to a metre what the stone of a cherry is to the earth. Such resolution allows us to establish that very weak electric fields have an (electromechanical) effect on selected cuticular structures. Whilst we have not yet fully developed the electrophysiological tests, the putative sensors are being now identified. Another piece of progress is the development of techniques to "make electric visible". How do we know about the existence of electric field arising between a flower and a pollinator such as a bee? How do we know about the field between an insect sitting on the surface of a leaf, the leaf, and the predatory wasp searching for its prey? These questions necessitate the characterisation of electric fields, in magnitude, dynamics and structure. For this objective we now have prototype dual electrometers and broadband pico ammeters that can report on electric field and electric induction respectively at the length scale required by leaves and insects, in the order of 5-10 cm and sometimes below in stable conditions. For smaller scale, more development is needed for the probes involved, accompanied by computer modelling. We have also made progress on the plant side of the question, establishing that contrary to prediction, the electro-activity of plants within an atmospheric electric gradient depends very much on its surface chemistry. This is this chemistry that will also interact with the insect, hence we are paying attention to this aspect. Also, we have completed the first stage of understanding the direct role of atmospheric potential gradient on the ballooning behaviour of spiders. Since Darwin and Faraday, the suspicion was that both mild wind and electrostatic interactions were important to the ballooning behaviour of spiders, in which they cast thin strands of silk to create a "silk sail". We have demonstrated that the electric potential present in the atmosphere on fair weather days is sufficient to create enough force to make the spiders airborne. This answers the question asked by Darwin, eg. how can spiderlings alight on calm days, and also establishes a general mechanism by which trillions of insects and arachnids can be found flying in the atmosphere up to 5km altitude, even if they do not have wings. The biomass of airborne insects, and how it can move over large distances, between continents, is important to the spread of species in novel environments. In view of a changing climate, new territories become fertile for species to invade. It may be useful to be able to predict the spread of species and the reason how and why they can or could do so in the near future. Progress was made in identifying putative electroreceptive structures on treehoppers, discovering a new species of treehopper in the process of doing that! The peculiar morphology of treehoppers is currently modelled mathematically to investigate the possible benefits of cuticular extensions in the process of electroreception.
The results with the new laser technology, although it has suffered teething problems, is beyond state of the art. In general, as mesoscale electric field imaging is not very well developed in physics, there is ample space for further instrumentation development. Mindful of the limitation in scope and length of this project, we consider our activities as innovative with this respect, but are also conscious of the focus we must apply to deliver on the objectives. Fortunately, we have excellent contacts with experts in the UK, and in the EU, that contribute to our progress. We have generated two review and integrative publications with EU colleagues that contribute to set up the large scope of the roles of electrostatics, atmospheric electricity and bio-meteorology. We do communicate our progress with colleagues in the atmospheric physics and biometeorology communities, as much as we can and inasmuch useful. More specifically, we expect to be able to contribute broadly and specifically to a further and deeper and broader appreciation of the role of weak electric fields and triboelectrification in animals, plants and their possible role in adapted behavioural strategies in the course of biological evolution. As sated above as well, we anticipate our activities to have an impact on our understanding of the effects of anthropogenic "industrial and post-industrial electrification" of the natural and human environments.