The spectral sensitivity of Drosophila photoreceptors

Abstract

Drosophila melanogaster has long been a popular model insect species, due in large part to the availability of genetic tools and is fast becoming the model for insect colour vision. Key to understanding colour reception in Drosophila is in-depth knowledge of spectral inputs and downstream neural processing. While recent studies have sparked renewed interest in colour processing in Drosophila, photoreceptor spectral sensitivity measurements have yet to be carried out in vivo. We have fully characterised the spectral input to the motion and colour vision pathways, and directly measured the effects of spectral modulating factors, screening pigment density and carotenoid-based ocular pigments. All receptor sensitivities had significant shifts in spectral sensitivity compared to previous measurements. Notably, the spectral range of the Rh6 visual pigment is substantially broadened and its peak sensitivity is shifted by 92 nm from 508 to 600 nm. We show that this deviation can be explained by transmission of long wavelengths through the red screening pigment and by the presence of the blue-absorbing filter in the R7y receptors. Further, we tested direct interactions between inner and outer photoreceptors using selective recovery of activity in photoreceptor pairs.

A visual pathway for skylight polarization processing in Drosophila

“…Within a narrow strip of skyward-facing ommatidia in each eye, known as the dorsal rim area (DRA), each R7/R8 pair is sensitive to a different angle of polarization (AoP, also referred to as the e-vector orientation), organized in a 'polarotopic' fashion ( Figure 1A ). This specialized array of polarization detectors covers the complete 180° range of orientations and, with a peak spectral sensitivity to UV light, is well-suited to sensing the patterns of polarized light in the sky ( Feiler et al, 1992 ; Salcedo et al, 1999 ; Sharkey et al, 2020 ; Weir et al, 2016 ). A previous characterization of DRA R7/R8 in Drosophila established their visual response properties and the spatial organization of their preferred angles of polarization ( Weir et al, 2016 ).…”

Crumbs and the apical spectrin cytoskeleton regulate R8 cell fate in the Drosophila eye

“…The rhabdomeres of the R7 and R8 photoreceptor cells are arranged in tandem and share the same optic path, with the R7 cell positioned distally and the R8 cell positioned proximally ( Fig 1A and 1A’ ) [ 4 ]. Each photoreceptor cell expresses a specific rhodopsin, a photosensitive G protein-coupled receptor with a distinct spectral sensitivity [ 5 , 6 ]. Expression of distinct rhodopsins in different photoreceptor cells allows each cell to respond to specific wavelengths of light and prevent sensory overlap.…”

An Inexpensive, High-Precision, Modular Spherical Treadmill Setup Optimized for Drosophila Experiments

“…An important consideration for measuring visually guided behaviors is to use illumination that minimally interferes with the animal's vision. The most practical solution is to use NIR illumination since fly vision is insensitive to these longer wavelengths (Sharkey et al, 2020), but most camera sensors measure it well. As we operate our camera at high frame rates and with a fixed aperture lens, intense illumination is essential for reliable sphere tracking, yet the light cannot be so intense that it saturates regions of the image (due to the limited dynamic range of any camera).…”