Overexpressing temperature-sensitive dynamin decelerates phototransduction and bundles microtubules in drosophila photoreceptors

shibire(ts1), a temperature-sensitive mutation of the Drosophila gene encoding a Dynamin orthologue, blocks vesicle endocytosis and thus synaptic transmission, at elevated, or restrictive temperatures. By targeted Gal4 expression, UAS-shibire(ts1) has been used to dissect neuronal circuits. We investigated the effects of UAS-shibire(ts1) overexpression in Drosophila photoreceptors at permissive (19 degrees C) and restrictive (31 degrees C) temperatures. At 19 degrees C, overexpression of UAS-shi(ts1) causes decelerated phototransduction and reduced neurotransmitter release. This phenotype is exacerbated with dark adaptation, age and in white mutants. Photoreceptors overexpressing UAS-shibire(ts1) contain terminals with widespread vacuolated mitochondria, reduced numbers of vesicles and bundled microtubules. Immuno-electron microscopy reveals that the latter are dynamin coated. Further, the microtubule phenotype is not restricted to photoreceptors, as UAS-shibire(ts1) overexpression in lamina cells also bundles microtubules. We conclude that dynamin has multiple functions that are interrupted by UAS-shibire(ts1) overexpression in Drosophila photoreceptors, destabilizing their neural communication irreversibly at previously reported permissive temperatures

Multiple spectral inputs improve motion discrimination in the Drosophila visual system

Color and motion information are thought to be channeled through separate neural pathways, but it remains unclear whether and how these pathways interact to improve motion perception. In insects, such as Drosophila, it has long been believed that motion information is fed exclusively by one spectral class of photoreceptor, so-called R1 to R6 cells; whereas R7 and R8 photoreceptors, which exist in multiple spectral classes, subserve color vision. Here, we report that R7 and R8 also contribute to the motion pathway. By using electrophysiological, optical, and behavioral assays, we found that R7/R8 information converge with and shape the motion pathway output, explaining flies’ broadly tuned optomotor behavior by its composite responses. Our results demonstrate that inputs from photoreceptors of different spectral sensitivities improve motion discrimination, increasing robustness of perception

Supplementary Material for: The Killer Fly Hunger Games: Target Size and Speed Predict Decision to Pursuit

Predatory animals have evolved to optimally detect their prey using exquisite sensory systems such as vision, olfaction and hearing. It may not be so surprising that vertebrates, with large central nervous systems, excel at predatory behaviors. More striking is the fact that many tiny insects, with their miniscule brains and scaled down nerve cords, are also ferocious, highly successful predators. For predation, it is important to determine whether a prey is suitable before initiating pursuit. This is paramount since pursuing a prey that is too large to capture, subdue or dispatch will generate a substantial metabolic cost (in the form of muscle output) without any chance of metabolic gain (in the form of food). In addition, during all pursuits, the predator breaks its potential camouflage and thus runs the risk of becoming prey itself. Many insects use their eyes to initially detect and subsequently pursue prey. Dragonflies, which are extremely efficient predators, therefore have huge eyes with relatively high spatial resolution that allow efficient prey size estimation before initiating pursuit. However, much smaller insects, such as killer flies, also visualize and successfully pursue prey. This is an impressive behavior since the small size of the killer fly naturally limits the neural capacity and also the spatial resolution provided by the compound eye. Despite this, we here show that killer flies efficiently pursue natural <i>(Drosophila melanogaster)</i> and artificial (beads) prey. The natural pursuits are initiated at a distance of 7.9 ± 2.9 cm, which we show is too far away to allow for distance estimation using binocular disparities. Moreover, we show that rather than estimating absolute prey size prior to launching the attack, as dragonflies do, killer flies attack with high probability when the ratio of the prey's subtended retinal velocity and retinal size is 0.37. We also show that killer flies will respond to a stimulus of an angular size that is smaller than that of the photoreceptor acceptance angle, and that the predatory response is strongly modulated by the metabolic state. Our data thus provide an exciting example of a loosely designed matched filter to <i>Drosophila</i>, but one which will still generate successful pursuits of other suitable prey