Figure 1. Different pigment patterns of D. rerio and D. albolineatus.

(a) D. rerio have interstripes with intervening stripes. The primary interstripe (1i) is first to develop, followed by primary stripes of melanophores (1m) and secondary interstripes (2i) and stripes (2m)⁴². Xanthophores (lower, inset) and melanophores are segregated spatially. D. al-bolineatus develop only a single incomplete interstripe, and melanophores and xanthophores are intermingled across the flank.

(b) Early in adult pigment pattern development in D. rerio (stage AR ⁴²), xanthophores had not yet differentiated and only adult iridophores (blue arrowhead) and residual early larval melano-phores were observed hypodermally. At the same stage in D. albolineatus, numerous xantho-phores (green arrowheads) had differentiated hypodermally and extra-hypodermally. hm, horizontal myoseptum; v, vertebral column; da, dorsal aorta.

(c) In comparison to D. rerio, xanthophores of D. albolineatus developed precociously. Shown are mean±s.e.m. days post-fertilization when pigment cells of each class first appeared (species difference across all classes, F_2,18=158, P<0.001; n=5 D. rerio; n=3 D. albolineatus).

Scale bars,1 mm (a upper); 200 μm (a lower); 60 μm (b).