title: Neuronal connectome of a sensory-motor circuit for visual navigation.
abstract: 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.
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Randel
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Albina
authors.initials: A
authors.lastname: Asadulina
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Bezares-Calderón
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Csaba
authors.initials: C
authors.lastname: Verasztó
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Williams
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Conzelmann
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Réza
authors.initials: R
authors.lastname: Shahidi
authors.affiliation: Max Planck Institute for Developmental Biology, Tübingen, Germany.
authors.forename: Gáspár
authors.initials: G
authors.lastname: Jékely
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000845:Annelida / Q000502:physiology*; D001522:Behavior, Animal; D063132:Connectome; D020869:Gene Expression Profiling; D017403:In Situ Hybridization; D007395:Interneurons / Q000502:physiology*; D008027:Light; D046529:Microscopy, Electron, Transmission; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D014785:Vision, Ocular
chemical_list: D018377:Neurotransmitter Agents
keywords: Platynereis; annelid; connectomics; eye evolution; neuroscience; phototaxis; platynereis dumerilii