loading two brains
0 traced neurons · Danio rerio larva
0 inferred connections
0 neurons · Drosophila melanogaster
every synapse mapped, FlyWire 783
awaiting launch
NOW
WHAT THE FISH WANTS TO DO
every name below is a region that exists in the atlas and does this job in a real hunt
WHAT THEY FEEL · EVERY TRADE OF $FLYFISH
buy = the eyes converge and the fish swims closer · a buy above the 90th percentile of the last 24 hours = the strike · sell = the fish drifts back and gets hungrier
SCIENCE
The predator
Danio rerio, larva. 4,172 neurons, each one traced by hand and registered into a common brain, coloured here by the anatomical region its cell body actually falls in. The larval zebrafish is the only vertebrate whose entire brain has been recorded neuron by neuron while it was alive and behaving.
Kunst et al. 2019, Neuron. mapzebrain single neuron atlas and anatomical segmentation v2.0.1, 597 x 974 x 359 micrometre standard brain. Whole brain recording: Ahrens et al. 2013, Nature Methods.
The prey
Drosophila melanogaster. 139,248 neurons and 2.7 million connections, every one verified at the synapse. It is the only brain that has ever been wired in full. What you see running through it is the escape: the looming detector fires, then the giant fiber, then the muscle. Five milliseconds, in that order.
Dorkenwald et al. 2024, Nature. FlyWire 783. Annotations: Schlegel et al. 2024.
What we are not claiming
The fish connectome is not finished. What exists publicly is the traced atlas above, plus a whole brain electron microscopy volume still being proofread. The connections we run in the fish are inferred from arbors touching, within four micrometres, not verified synapse by synapse.
So the two brains are complete in different ways. The fly is fully wired. The fish was fully recorded. We say so rather than let you assume otherwise.
The hunt
Prey capture in a zebrafish larva is one of the best described behaviours in any vertebrate. Prey enters the visual field, the optic tectum builds a map of it, the pretectum commits, the eyes converge, a J turn aims the body, approach swims close the gap, and the mouth opens. The larva misses often. So does this one.
The strike lands with a probability between 0.15 and 0.85, from the distance at that moment and how hungry the fish is. Nothing is scripted.