Samples of two contacts cut the birth to adult clustering contrast by 88–90% in two C. elegans comparisons under a proximal node model

We tested whether the age rise in the fraction of spatially clustered connections remained at a fixed contact count. We used 5,712 released connection rows and source skeletons from eight C. elegans maps. The reference model samples distinct presynaptic skeleton nodes close to the target. We enumerated all pairs of observed contact records and all pairs of eligible reference nodes. This gives the exact expected clustering call for a uniform sample of two records. Released full-count fractions were 9.90% at birth and 19.42% and 18.61% in adults. Two-record fractions were 8.27%, 9.26% and 9.33%. The age contrasts fell by 89.6% and 87.9%. In 177 connection identities available in all eight maps, two-record fractions were 8.79% at birth and 8.67% and 6.70% in adults. Controls for repeated locations, muscle targets, region support and proximity cutoffs kept a much smaller two-record contrast. A selected panel of 22 connections with four records available in every map retained adult increases of 6.68 and 5.68 percentage points. The exact main result shows strong count sensitivity. It does not show that counts alone caused the full developmental contrast. One animal at most ages, two adults, sparse early counts and the spatial reference limit inference. The package preserves code, source hashes, per-connection data, figures, proofs, controls and repeat instructions.

C. elegans · connectome · development · synapse clustering · contact count · spatial null model · exact enumeration