Meeting Abstract
The fruit fly Drosophila melanogaster is sensitive to light and prefers certain light intensities. But lab-reared flies are often tested for vision in bright light conditions to obtain the best response. Similarly, scarce feeding during the late larval stage, which is common in nature, can lead to smaller flies contributing to a wide range of body and eye sizes which are not observed in lab colonies fed ad libitum. Flying with smaller eyes and under dimmer light conditions is challenging due to reduced signal-to-noise ratio affecting visual behaviors. To better understand the visual capabilities of flies in nature, it is thus important to study flies of different eye sizes and under different light intensities. In this study, we use a virtual reality flight arena and moving sinusoidal gratings to test how spatial acuity, temporal acuity and contrast threshold are affected at different light intensities in female flies that vary in eye size. We also investigate vision in often neglected male fruit flies under different light intensities and compare them to that of females. We show that as light intensity drops from 50.1 lx to 0.3 lx, it leads to reduced spatial acuity (females: from 0.1 to 0.06 cycles per degree, CPD, males: 0.1 to 0.04 CPD) and temporal acuity (females: from 50 Hz to 10 Hz, males: 25 Hz to 10 Hz), and higher contrast detection threshold (females: from 10% to 29%, males: 19% to 48%). We find no major sex-specific differences in visual abilities after accounting for eye size variation. While vision in both small (eye area 0.1 to 0.17 mm2) and large flies (0.17 to 0.23 mm2) reduce at 0.3 lx compared to 50.1 lx, small flies suffered more (spatial acuity: 0.03 vs 0.06 CPD, contrast threshold: 76% vs 57%, temporal acuity: 5 Hz vs 10 Hz). These results have implications to many visual behaviors in flies.
