With gap counts by partner type, side and chemical state fixed, 311 of 327 pairs were forced among 163 Ciona neurons

We asked if putative gap junctions join Ciona neurons with similar chemical partners. We used 163 neurons from one larva's released 2016 map. We fixed each neuron's gap counts by partner cell type, side and direct chemical state. The chemical state was no edge, one direction, or both directions. We enumerated all 648 feasible labelled gap graphs. All contained the same 311 of 327 recorded pairs. Independent binary integer optimization confirmed this count. Recorded mean input and output cosines were 0.354952 and 0.366782. The exact reference means were 0.354627 and 0.366653. The output-minus-input contrast had an exact upper tail fraction of 0.5324. Sampled degree and region-side controls left larger similarity excesses. Removing motor and midtail neurons left 93.9% of pairs forced. Removing the motor ganglion left 93.0% forced. The method shows how much freedom a count control leaves. It does not establish biological randomness or function. The data concern one animal and putative electrical contacts. The package contains source tables, label audits, enumeration and optimization code, provenance, results and figures.

connectome · Ciona intestinalis · gap junctions · chemical synapses · exact enumeration · constrained graphs · forced edges