Influence of female orientation and pigmentation on male positioning during courtship
Despite its emergence as a premier model for visual processing, little is known about object recognition in Drosophila. One possible explanation for this deficit is that Drosophila do not display behaviors typically associated with exemplary feats of object recognition, like the flower shape memory exhibited by bees. In addition, Drosophila eyes provide poor spatial resolution. Nevertheless, visual object recognition may be important during courtship. Because courtship occurs at a very close distance, flies could distinguish fine-scale pigmentation patterns. At a greater distance, a chasing male would have access to cues such as shape, size, and patterns of motion. To understand how courting male flies use vision, we developed a behavioral apparatus, dubbed "Flyatar," consisting of a remotely actuated fly dummy. We can modify the dummy's appearance, pattern of motion, and pheromone coating. Males will robustly court the dummy, enabling us to delineate the relative contributions of visual and other sensory cues to male courtship behavior. We are using Flyatar to examine how a male uses vision and chemosensation to position its body during chases. To have a chance at successful copulation, a male must position itself appropriately around the female. Male flies preferentially bias their chasing towards the female's abdomen, irrespective of her body orientation and direction of movement. This preference is maintained towards females that have been genetically altered to not produce pheromones, suggesting that males can distinguish different parts of the female body using vision alone. In addition, males demonstrate a preference for chasing objects painted specific shades, and are not strongly attracted towards very dark or very light objects. These results suggest that, though simple, visual object recognition nevertheless plays an important role in courtship behavior.
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