Animals use spatial differences in environmental light levels for visual navigation; however, how light inputs are translated into coordinated motor outputs remains poorly understood. Here we reconstruct the neuronal connectome of a four-eye visual circuit in the larva of the annelid Platynereis using serial-section transmission electron microscopy. In this 71-neuron circuit, photoreceptors connect via three layers of interneurons to motorneurons, which innervate trunk muscles. By combining eye ablations with behavioral experiments, we show that the circuit compares light on either side of the body and stimulates body bending upon left-right light imbalance during visual phototaxis. We also identified an interneuron motif that enhances sensitivity to different light intensity contrasts. The Platynereis eye circuit has the hallmarks of a visual system, including spatial light detection and contrast modulation, illustrating how image-forming eyes may have evolved via intermediate stages contrasting only a light and a dark field during a simple visual task.
High-resolution image stack of the Platynereis larval primary optic neuropil
High-resolution (1.13 nm/pixel) image stack (tiff series) of the Platynereis larval primary optic neuropil. Contains 4 layers of 22,304 x 5680 pixels.
Dryad_dataset1.tif
acetylated tubulin staining registered to the unbiased nuclear reference
Tiff stack of average acetylated tubulin staining registered to the unbiased nuclear reference of 3-day-old Platynereis larvae. The antibody labels cilia and the axonal scaffold (white).
Dryad_dataset2.tif
Average full-body gene expression patterns of r-opsin1, hdc and VAChT
RGB tiff stack of average registered full-body gene expression patterns of eye marker gene r-opsin1 (red) and neurotransmitter marker genes hdc (green) and VAChT (blue), created by RNA whole mount in situ hybridization in 3-day-old Platynereis larvae. Note that signal present in spinning glands, parapodia and chaetae of larvae is background.
Dryad_dataset3.tif
Average full-body gene expression patterns of VGluT, TrpH and ChAT
RGB tiff stack of average registered full-body gene expression patterns of neurotransmitter marker genes VGluT (red), TrpH (green) and ChAT (blue), created by RNA whole mount in situ hybridization in 3-day-old Platynereis larvae. Note that signal present in spinning glands, parapodia and chaetae of larvae is background.
Dryad_dataset4.tif
Average full-body gene expression patterns of gad, TyrH and dbh
RGB tiff stack of average registered full-body gene expression patterns of neurotransmitter marker genes gad (red), TyrH (green) and dbh (blue), created by RNA whole mount in situ hybridization in 3-day-old Platynereis larvae. Note that signal present in spinning glands and chaetae of larvae is background, however, signal in the parapodia in the TyrH (green) channel represents real gene expression.
Dryad_dataset5.tif
Double in situ hybridization for r-opsin1 and hdc
RGB tiff stack of raw data from high-resolution apical scan of double RNA whole mount in situ hybridization with r-opsin1 (red) and hdc (green) in 3-day-old Platynereis larvae. Larva is counterstained with acetylated tubulin antibody (blue) to show cilia and axonal scaffold.
Dryad_dataset6.tif
Blender file containing the complete virtual anatomical atlas of the Platynereis eye circuitry
Simplified 3D models of all neurons, synapses, muscles and ciliated cells are included. The file can be viewed with the Blender software http://www.blender.org/.
Dryad_dataset7.blend
Node ranking in the Platynereis eye circuitry
Node ranking in the Platynereis eye circuitry based on various centrality measures.
Dryad_dataset8.xlsx
3-day-old nuclear-stain whole-body reference template
Nuclear-stain whole-body reference template for 3-day-old (72 hours post fertilization) Platynereis larvae (tiff image stack). The whole-body nuclear-stain reference template was generated by the iterative registration of 40 individual scans.
Dryad_dataset9.tiff
Phototaxis ImageJ Macro
ImageJ macro used to score phototaxis videos.
Dryad_dataset10.ijm
Phototaxis videos of control and mecamylamine-treated larvae
Videos of phototaxis experiments. 3-day-old control larvae and larvae treated with 50 μm mecamylamine were imaged with 15 frames per second in a split phototaxis assay cuvette. The length of the cuvette is 15 mm. Directional white stimulus light was provided from the left. Each video is 600 frames. The videos are in Zeiss zvi format. The files were compressed with tar -jcvf archive_name.tar.bz2 directory_with_files/*, use tar –jxvf to uncompress them.
Dryad_dataset11.tar.bz2