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Fig. 8
Iridophores influenced melanophore pattern in xanthophore-deficient csf1r mutants.
(A,B) In stage-matched siblings treated with Mtz, a region on the tail from which iridophores have been ablated (dashed yellow lines in B) exhibits more melanophores than the corresponding region of the control larva (shown here at ~8.5 SSL). Both larvae were treated with epinephrine immediately before imaging. (C,D) Iridophore ablation at the mid-trunk region (dashed yellow lines in D) likewise resulted in increased numbers of melanophores compared to stage-matched control (C)(shown here at ~10.2 SSL). Note that some iridophores have regenerated within previously ablated regions and that melanophores are present at the left edge of the ablated region, adjacent to remaining interstripe iridophores. Larvae in these images were not treated with epinephrine. (E) Quantification of melanophore distributions within dorsal–ventral regions of the flank for larvae that were uninjected but treated with Mtz (left) and for regions of injected, Mtz-treated larvae from which iridophores were unablated (middle) or ablated (right). Plots show means±SE within each region. Asterisk denotes the residual interstripe in csf1r mutants, where melanophore numbers differed significantly between unablated and ablated regions (paired t = 5.6, d.f. = 2, P<0.05). (F,G) Details showing melanophore behaviors in an uninjected control larva (F) and an injected larva (G) in the region of iridophore ablation. Day 0 panels show initial distribution of iridophores and melanophores, prior to Mtz treatment (7.0 SSL). Following iridophore ablation (G), some melanophores moved short distances ventrally (red arrows at d0 and d2 show starting and stopping positions of two melanophores). Melanophores also differentiated within the ablated region (dashed red circles in G, d2); dashed orange circle in G, d7 shows a lightly melanized cell just beneath the surface of the myotome that emerges within the skin by d8. In unablated individuals (F), melanophores typically differentiated further ventrally at sites lacking iridophores (an exception is the left-most melanophore that appeared at d7). Also see Figure S3C. (H) Detail from another individual showing a lightly melanized cell initially near an iridophore that was ablated (blue arrowhead); the melanophore subsequently translocated to settle adjacent to another iridophore. All larvae in F–H were treated with epinephrine. (Total sample size, N = 55.) Scale bars: in (A) 200 μm for (A,C); in (B) 400 μm for (D); in (F, d0) 80 μm for (F,G); in (H, d0) 20 μm for (H).