Manuscript and Data

Fish1: A Connectomic Resource for the Larval Zebrafish Brain

A correlated light and electron microscopy (CLEM) dataset from a 7-day-old larval zebrafish, spanning the brain and anterior spinal cord with over 180,000 segmented soma, 40,000 molecularly annotated neurons, and 30 million synapses. Excitatory (vglut2a+) and inhibitory (gad1b+) neurons are molecularly annotated at single-cell resolution. Published on bioRxiv, June 2025.

Abstract

We present a correlated light and electron microscopy (CLEM) dataset from a 7-day-old larval zebrafish, integrating confocal imaging of genetically labeled excitatory (vglut2a) and inhibitory (gad1b) neurons with nanometer-resolution serial section EM. The dataset spans the brain and anterior spinal cord, capturing >180,000 segmented soma, >40,000 molecularly annotated neurons, and 30 million synapses, most of which were classified as excitatory, inhibitory, or modulatory. To characterize the directional flow of activity across the brain, we compute region-wise input and output drive indices that quantify synaptic polarity and molecular labeling — at single cell resolution. We illustrate the dataset's utility by dissecting and validating circuits in three distinct systems: water flow direction encoding in the lateral line, recurrent excitation and contralateral inhibition in a hindbrain motion integrator, and functionally relevant targeted long-range projections from a tegmental excitatory nucleus, demonstrating that this resource enables rigorous hypothesis testing or exploratory-driven novel circuit analysis. The dataset is integrated into an open-access platform optimized to facilitate community reconstruction and discovery efforts throughout the larval zebrafish brain.


Correlated Light and Electron Microscopy

CLEM Overlays

Multimodal overlay combining electron microscopy with confocal fluorescence data. Excitatory (vglut2a+) and inhibitory (gad1b+) neurotransmitter identities are visualized alongside the vasculature (kdrl+) using transgenic reporter lines. Cellular polarities are assigned based on EM-defined soma overlaps.

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Semantic Segmentation Masks

Tissue Type

Global classification of tissue types.

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Subcompartment Classification

Classification of cellular subcompartments.

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Semantic Artifact Mask

Identified imaging and processing artifacts.

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Evaluations

Supervoxel Merge Rates

Evaluation of merge errors in the supervoxel segmentation.

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Ouroboros Merge Rates

Evaluation of merge errors in the Ouroboros agglomeration.

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Automatic Synapse Predictions

Annotation of true positive, false positive, and false negative synaptic predictions.

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Automatic Subcompartment Classification

Evaluation of subcompartment classification (axon, dendrite, glia) accuracy.

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EI Polarity Assignment

Evaluation of Excitatory/Inhibitory classification accuracy.

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EI Morphological Differences

Evaluation of the morphological differences in vesicle appearance between excitatory and inhibitory neurons.

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Circuits

Tegmental Excitatory Nucleus

Characterization of the synaptic outputs of a tegmental excitatory nucleus (TEN).

Hindbrain Motion Integrator

Connectomic analysis of a hindbrain integrator circuit and its role in sensorimotor integration.