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Contribution of photoreceptor subtypes to spectral wavelength preference in Drosophila

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The visual systems of most species contain photoreceptors with distinct spectral sensitivities that allow animals to distinguish lights by their spectral composition. In Drosophila, photoreceptors R1-R6 have the same spectral sensitivity throughout the eye and are responsible for motion detection. In contrast, photoreceptors R7 and R8 exhibit heterogeneity and are important for color vision. We investigated how photoreceptor types contribute to the attractiveness of light by blocking the function of certain subsets and by measuring differential phototaxis between spectrally different lights. In a "UV vs. blue" choice, flies with only R1-R6, as well as flies with only R7/R8 photoreceptors, preferred blue, suggesting a nonadditive interaction between the two major subsystems. Flies defective for UV-sensitive R7 function preferred blue, whereas flies defective for either type of R8 (blue- or green-sensitive) preferred UV. In a "blue vs. green" choice, flies defective for R8 (blue) preferred green, whereas those defective for R8 (green) preferred blue. Involvement of all photoreceptors [R1-R6, R7, R8 (blue), R8 (green)] distinguishes phototaxis from motion detection that is mediated exclusively by R1-R6.
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... Drosophila suzukii is highly sensitive to temperature, humidity, and light (Tochen et al. 2014(Tochen et al. , 2016Guédot et al. 2018), and suboptimal conditions can impact development, behavior, and survival of all developmental stages (Kinjo et al. 2014;Ryan et al. 2016;Tochen et al. 2016;Zerulla et al. 2017;Evans et al. 2018). Light is a major driver of D. suzukii behavior, since the flies are sensitive to wavelengths between 300 and 660 nm (Hardie 1979;Yamaguchi et al. 2010;Kelber and Henze 2013;Schnaitmann et al. 2013;Fountain et al. 2020) and attracted to or repelled by different wavelengths (Lee et al. 2013;Rice et al. 2016;Little et al. 2018Little et al. , 2019. Ultraviolet (UV; < 400 nm) light may be especially important, since it is used by insects for navigation through vegetation and orientation relative to the sky (Weir and Dickinson 2012;Cronin and Bok 2016). ...
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