The effects of target contrast on Drosophila courtship
Many animals use visual cues such as object shape, color and motion to detect and pursue conspecific mates. Contrast is another possibly informative visual cue, but has not been studied in great detail. In this study, we presented male Drosophila melanogaster with small, fly-sized, moving objects painted either black, white or gray to test whether they use contrast cues to identify mates. We found that males frequently chased gray objects and rarely chased white or black objects. Although males started chasing black objects as often as gray objects, the resulting chases were much shorter. To test whether the attraction to gray objects was mediated via contrast, we fabricated black and gray behavioral chambers. However, wild-type males almost never chased any objects in these darkly colored chambers. To circumvent this limitation, we increased baseline levels of chasing by thermogenetically activating P1 neurons to promote courtship. Males with thermogenetically activated P1 neurons maintained a similar preference for gray objects despite elevated levels of courtship behavior. When placed in a black chamber, males with activated P1 neurons switched their preference and chased black objects more than gray objects. We also tested whether males use contrast cues to orient to particular parts of the female's body during courtship. When presented with moving objects painted two colors, males positioned themselves next to the gray half regardless of whether the other half was painted black or white. These results suggest that males can use contrast to recognize potential mates and to position themselves during courtship.
© 2019 Published by The Company of Biologists Ltd. Received 14 March 2019; Accepted 11 July 2019. We thank D. Anderson for providing the P1 split-GAL4 line and A. Sustar for her help with backcrossing all fly lines into a Canton-S background. We also thank S. Safarik for his help with technical details relating to the Flyatar apparatus, and Kristin Branson, Alice Robie and Juan Rodriguez-Gonzalez for the Duotrax software used to track wings. The authors declare no competing or financial interests. Author contributions: Conceptualization: S.A., M.H.D.; Methodology: S.A., M.H.D.; Software: S.A.; Validation: S.A.; Formal analysis: S.A.; Investigation: S.A.; Resources: M.H.D.; Data curation: S.A.; Writing - original draft: S.A.; Writing - review & editing: S.A., M.H.D.; Visualization: S.A., M.H.D.; Supervision: M.H.D.; Funding acquisition: M.H.D. This material is based upon work supported by the Paul G. Allen Family Foundation and the National Science Foundation Graduate Research Fellowship Program under grant no. DGE-0718124. Data availability: Data are available from the Dryad Digital Repository (Agrawal and Dickinson, 2019): https://doi.org/10.5061/dryad.k74670v Supplementary information: Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.203414.supplemental
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Supplemental Material - JEB203414supp.pdf