Complete male fruit fly nervous-system connectome (166,000 neurons), reconstructed with Google AI, published in Cell
On Sept 3, 2026 Google Research, HHMI Janelia and Cambridge (MRC LMB) announced peer-reviewed publication in Cell of the first complete connectome of an adult male fruit fly's central nervous system (brain plus ventral nerve cord). It maps more than 166,000 neurons and about 125 million synapses in 11,691 cell types. Google calls it the largest brain map by neuron count to date. Google's AI segmented the electron microscopy data, and Janelia and Cambridge teams proofread and annotated it. The map allows the first whole-CNS comparison of male and female wiring in an animal with complex social behavior.
Key facts
- >166,000 neurons and ~125 million synapses; 11,691 neuron types in the male CNS (Google blog/Google Research)
- First complete male fruit fly CNS map; builds on the 2024 complete female fruit fly brain connectome (FlyWire)
- Sex differences: most neurons are the same in both sexes; a minority are sex-specific, and 'dimorphic' neurons exist in both sexes but wire differently, mainly in courtship- and aggression-related circuits
- Method: thin sections imaged by focused ion beam scanning electron microscopy; Google's flood-filling networks and its PATHFINDER reconstruction system (trained partly on synthetic neurons) turned millions of 2D images into 3D neurons; human experts at Janelia and Cambridge proofread and labeled them
- Papers: Cell, 'Sexual dimorphism in the complete connectome of the Drosophila male central nervous system', with companion papers; the Google blog links doi 10.1016/j.cell.2026.08.014, 10.1016/j.cell.2026.08.016 and Current Biology 10.1016/j.cub.2026.08.013; a preprint appeared on bioRxiv in Oct 2025
- Data: Janelia 'male-cns' dataset, explorable in Neuroglancer
- Google Research's post also cites new Nature papers on an elephantnose fish cerebellum-like circuit and a zebrafish whole-brain connectome (not separately verified here)
Science result
- Field
- biology / neuroscience / connectomics
- Problem
- Complete synapse-level wiring diagram of an adult male Drosophila central nervous system
- Result
- Full male CNS connectome: >166,000 neurons, ~125M synapses, 11,691 cell types; systematic map of sex-specific and dimorphic neurons
- AI system
- Google flood-filling networks, PATHFINDER
- Human role
- Human-led with AI tools: AI segmentation of EM data; human proofreading, cell typing and analysis
- Verification
- Peer-reviewed in Cell (Sept 2026)
- Status
- confirmed
What happened
A years-long collaboration between HHMI Janelia, Google Research, the MRC Laboratory of Molecular Biology and the University of Cambridge published the first complete wiring diagram of an adult male fruit fly's central nervous system, covering both the brain and the ventral nerve cord. Janelia imaged the tissue with focused ion beam electron microscopy. Google's machine-learning segmentation reconstructed the 3D shapes of more than 166,000 neurons from millions of 2D images, and human teams proofread and classified them into 11,691 types. Comparing it with the female brain map from 2024 shows which neurons are sex-specific or wired differently between sexes, mostly in circuits for courtship and aggression.
Why it matters
Connectomics is one of the clearest cases where AI turns an impossible manual task into a feasible one. This is the largest complete brain map by neuron count, and the first that allows a whole-nervous-system comparison of the two sexes. Google says the same pipeline is being scaled toward vertebrate brains.
Changelog
- 2026-09-30: created (official-blog audit)
Sources (8)
- officialGoogle Research: A connectomics milestone: mapping the complete male fruit fly brain
- officialGoogle blog: 5 amazing visuals show how the male fruit fly's brain map is advancing neuroscience
- paperCell paper (doi 10.1016/j.cell.2026.08.014)
- paperCell companion paper (doi)
- paperCurrent Biology companion paper (doi)
- officialJanelia: Researchers reveal connectome of the male fruit fly central nervous system
- docsJanelia FlyEM: male CNS connectome dataset
- pressNeuroscience News: Microscopy and AI decipher fruit fly neural architecture
id: 2026-09-03-male-fruit-fly-connectome · updated 2026-09-30 · open in the interactive timeline