Regular features along the dendritic shaft of the fish. (A) Spine necks forming regular linear arrays over the shaft surface, revealed in glancing confocal sections (shaft axis is vertical). (B) Periodic arrangement incorporating linear arrays of spines (e.g., circles) in a region of high population density. (C) Diffraction pattern of B, showing two pairs of peaks arranged with approximate mirror symmetry about a vertical axis; the distance of these peaks from the equator indicates that the periodicities repeat every 1.25 μm. (D and E) Filtered images revealing the paths traced by lines of spines on the near (N) and far (F) sides of the shaft, made by including only terms associated with the separate pairs of peaks within the masks (see Materials and Methods). (F) Filtered image made by including terms within all of the masked areas in C; the pair of vertical lines indicate the radius at which the modulations have the greatest contrast. Here and in Figs. , , , and , the contrast has been inverted so that areas of high fluorescence appear dark. (Scale bars, 1.0 μm.)