Abstract
Visually evoked escape flight initiation in Drosophila, according to the accepted account, involves a rapid extension of the middle legs that propels the fly into the air while the wings are still folded. This description has remained unchallenged and is accounted for in terms of the activation of a simple neural circuit, the Giant fibre (GF) system. The accepted description of escape is however inconsistent with the sequence of events recorded when the GF system is stimulated. Specifically, previous electrophysiological recordings have shown that the wing depressor muscles are activated before the wings are in a position to be depressed because they have not yet been elevated. Here we show that the accepted behavioural description is wrong. Escape flight initiation actually begins with wing elevation. The current model of the GF system is revised to account for the actual sequence of events that occur when a fly escapes.
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Abbreviations
- DLMn:
-
Dorsal longitudinal flight motoneuron
- GF:
-
Giant fibre
- PSI:
-
Peripherally synapsing interneuron
- TTMn:
-
Tergotrochanteral muscle motoneuron
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Acknowledgements
We thank the Rutherford Appleton Laboratory and the Engineering and Physical Sciences Research Council for the loan of the Kodak Motion Corder SR-Ultra camera used in this study. György Kemenes advised on the statistical analysis and Jane Davies and Jonathan Bacon provided helpful comments on the manuscript.
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Fig. S1
The approaching object stimulus. a The experimental set-up. The disc’s distance from the funnel when the two strains of fly initiated an escape response is also indicated. b The accelerating approach of the disk was plotted by filming five descents (each point is the mean of five observations). The curve was extended to calculate the mean time to collision (234.4 ms ± 3.9 SEM). The position of the descending disc when escape is initiated is also indicated. (GIF 29 kb)
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Hammond, S., O’Shea, M. Escape flight initiation in the fly. J Comp Physiol A 193, 471–476 (2007). https://doi.org/10.1007/s00359-006-0203-9
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DOI: https://doi.org/10.1007/s00359-006-0203-9