A Complete Male Fruit Fly Connectome Reveals Sex Differences in the Brain
When a male fruit fly pursues a female, it uses vision to track her position, detects odors and pheromones, and samples gustatory information by touching her with its forelegs. Males can also detect courtship song produced by other males through their antennae, altering their locomotor activity and courtship behavior in response. Male and female flies receive much of the same sensory information from the outside world, yet they can respond in strikingly different ways. At what point in the nervous system do these differences arise? By comparing neural connections between the sexes neuron by neuron, researchers can begin to identify where shared sensory signals are routed toward different behavioral outputs.
In 2026, researchers completed a connectome of the entire central nervous system of an adult male fruit fly, Drosophila melanogaster. The reconstruction spans the brain and optic lobes through the ventral nerve cord, while preserving the neck connective that links the brain to the nerve cord. Using seven enhanced focused ion beam scanning electron microscopy systems, the researchers spent about a year acquiring images at an isotropic resolution of 8 × 8 × 8 nm, producing a dataset of roughly 160 teravoxels. After automated segmentation, 29 expert proofreaders spent approximately three years inspecting and correcting the reconstructed neurons.
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