Determining navigational mechanisms in migratory insect pests: a feasibility study

Lead Research Organisation: Rothamsted Research
Department Name: Computational & Systems Biology



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Reynolds AM (2016) Orientation in high-flying migrant insects in relation to flows: mechanisms and strategies. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

Description We identified putative mechanisms by which high-flying nocturnal migratory insects can sense the wind direction and orientate, so as to fly downwind. We recognised that "flight noise" created by beating wings does not interfere with these mechanisms. We have identified a new turbulence mechanism and published a paper in Phil. Trans. Roy. Soc. B
Exploitation Route Our findings will lead to improved predictions and modelling of the flight patterns of migratory insects, many of which are of agricultural significance. A paper describing some of our key findings is being prepared for submission to the Philosophical Transactions Royal Society B.
Sectors Agriculture, Food and Drink

Description Visiting Sanjay Sane 
Organisation National Centre for Biological Science (NCBS)
Country India 
Sector Academic/University 
PI Contribution Rothamsted Research has made seminal contributions to the monitoring of migratory pests through the employment of vertical looking radar that allows identification of individual migrating insects up to 1 km above the ground. Data from these studies have been used to develop and validate a predictive model of migration (Reynolds et al. 2009, 2010, 2010). This model explains how migrants can use wind-mediate cues to locate the fastest airstreams and to orientate downwind, a behaviour known as 'common orientation'; two facets of insect migration that have puzzled researchers for more than 40 years. These advances have the potential to improve considerably models of long-range migration and so better predict the arrival of migratory pests and beneficials.fluctuations indicate the mean wind flow?
Collaborator Contribution Progress at Rothamsted is being hindered by a lack of understanding of the sense organs involved in insect navigation, enabling inferences to be made the migratory propensity of different species under different meteorological conditions. Prof. Sane's group is uniquely positioned to provide this information. His multidisciplinary group is concerned with the physics, neurobiology and ecophysiology of insect flight. They utilize diverse techniques such as high-speed videography, behavioural measurements, neuroanatomy and neurophysiology; techniques that are ideally suited for the identification of orientation mechanisms. We discussed how to bring our expertise and understanding together. Ideas generated in discussions n with Prof. Sane and co-workers at NCBS on how migratory pests/ beneficials utilize the wind provided new insight into turbulence cues used by migratory insect pests for orientation. These insights will improve predictive models of long-range models by better coupling innate behaviours and meteorological conditions.During the visit we met several times a day for hourly discussions, pooling our knowledge of the two mechanisms. We agreed that it is likely that in most cases the cues for orientation are not exclusive but are instead hierarchical, with wind-mediated cues being predominate in many cases. Nonetheless, we also agreed that the radar observations can be explained in a self-consistent way without reference to optomotor responses but that this does not preclude their absence since it is now realized that some nocturnal insects have remarkable visual abilities (as evidenced by recent studies of dung beetles which have been reported by Marie Dacke and Eric Warrant at Lund University to use weak celestial cues such as polarized moonlight and the milky way for path-straightening). Moreover, optomotor effects in themselves are not sufficient to explain orientation and layering because (a) they cannot account for observed headings having right-of-the-mean-wind-line offsets and (b) because frequent stimulation of sensilla is required for maintenance of the 'migration mode' through the production of octopamine. Air puffs mediate a response; and once initiated sensitise indirect flight muscles (that are required for sustained flight). Lots of stimulation leads to continuous flight. We agreed that 'fight noise' due to wing beating will be anisotropic (i.e., dependent upon orientation with respect to the mean wind direction) and will amplify rather than mask wind-mediated cues for orientation. In particular, any disturbance of the wake due to surrounding atmospheric turbulence will almost certainly be felt by the migrant. In summary: the turbulence mechanism can fully explain current observations; whereas no optomotor mechanism can fully explain the data. Nonetheless, it may be possible to devise experiments or analysis of data to set bounds on the relative importance of the optomotor mechanism. Following the visit we continued to interact via email and produced the following paper Reynolds A.M., Reynolds D., Sane S.P., Hu G., Chapman J.W. 2016. Orientation in migrating insects in relation to flows: mechanisms and strategies. Philosophical Transactions Royal Society B 371: 20150392.
Impact This is a multi-disciplinary collaboration concerned with the physics, neurobiology and ecophysiology of insect flight. The collaboration has resulted in one joint publication Reynolds A.M., Reynolds D., Sane S.P., Hu G., Chapman J.W. 2016. Orientation in migrating insects in relation to flows: mechanisms and strategies. Philosophical Transactions Royal Society B 371: 20150392.
Start Year 2015