Fig. 4: Morphological features of individual projection neurons in different Drosophila species.

a Schematic depicting the technique used to dye-label a projection neuron innervating a given glomerulus: a glomerulus is used as a landmark for a first round of photo-labeling (blue dashed outline) during which the projection neurons connected to the targeted glomerulus are lightly photo-labeled; dye is electroporated in one of the photo-labeled projection neurons such that a single projection neuron is dye-labeled. b A projection neuron innervating the DL2d (upper row), DC3 (middle row) and VM5v (lower row) glomeruli were dye-labeled in D. melanogaster (left column), D. simulans (middle column) and D. sechellia (right column); the axonal termini these neurons extend in the mushroom body were imaged. Scale bar is 50 µm. c Various morphological features displayed by projection neurons in the mushroom body were quantified and compared across species (red: D. melanogaster; blue: D. simulans; green: D. sechellia). The statistical significance, or p-value, was measured using the Mann–Whitney U test (*p-value < 0.5, **p-value < 0.01, ***p-value < 0.001; n = 5, standard deviation from mean is shown). See Supplementary Table 1 for quantifications. All source data used in this figure are provided in the Source Data file.