Fig. 6. Analysis of the dynamic behavior of amacrine neurites within the IPL reveals extensive remodeling. Changes in neurite length over a period of 30 minutes were measured for amacrine cells with extensive lateral arbors in the IPL and used to calculate average motility rates. (A) Changes in length for three neurites (1,2,3) from the lateral arbor of an amacrine cell (CFP⁺ line Q11, 58 hpf) are plotted in B. (C) Average extension and retraction rates of processes within the IPL were found to be similar (0.16±0.06 µm/minute and 0.15±0.04 µm/minute, respectively; n=3 cells, 24 processes; P>0.05; Mann-Whitney rank sum test). (D) Time-lapse images of an amacrine cell (54 hpf at 0') digitally rotated to provide a clearer view of its lateral arbor. Extensions (e) and retractions (r) of neurites within the IPL resulted in dramatic changes of the territory occupied by the lateral arbor (see E). Occasionally, neurite outgrowth towards the outer retina, from the lateral arbor (o at 0') or from the cell body (o at 80') was observed. (E) Time-lapse images of the amacrine cell in D digitally rotated to provide en face views of the lateral arbor. The extent of the cell's lateral territory is outlined in white and the location of the presumed Golgi (bright spot in the cell body in D) is depicted by a black oval.