Fig. 3. Pigment pattern metamorphosis differs between D. rerio (A-E') and D. nigrofasciatus (F-J'). Panels shown are of selected days from a complete image series for individual, representative larvae. In A and F, the sites of early larval melanophore stripes are indicated at the dorsal and ventral margins of the myotomes (horizontal arrowheads), and at the horizontal myoseptum (squares). In D. rerio, pigment pattern metamorphosis begins with the differentiation of pioneer metamorphic melanophores over the ventral myotomes (A, arrow), with additional metamorphic melanophores (B, arrow) appearing both dorsally and ventrally over a period of several days (B-D). Adult primary stripes become evident as dispersed melanophores migrate to sites of stripe formation and additional metamorphic melanophores differentiate within the stripes (D,E). A few early larval melanophores move from the horizontal myoseptum to join the adult dorsal primary melanophore stripe (C-E, arrowheads). Near the end of pigment pattern metamorphosis the larvae have developed an adult dorsal primary melanophore stripe and an adult ventral primary melanophore stripe (1D, 1V, respectively, in panel E). The adult ventral primary melanophore stripe develops just ventral to the level of the aorta (a, in panel E), about halfway between the horizontal myoseptum and the ventral margin of the myotomes (E'). In D. nigrofasciatus, pigment pattern metamorphosis begins with early larval melanophores becoming displaced from the larval stripes (F, melanophores 1-6). Whereas some metamorphic melanophores differentiate de novo (G,H, arrows), these are markedly fewer than in D. rerio. As metamorphosis proceeds, melanophores initially present in the ventral early larval stripe (H, arrowheads) become increasingly distant from the ventral margin of the myotomes. By late stages of pigment pattern metamorphosis, a complete adult ventral primary melanophore stripe has formed (J), and both dorsal and ventral stripes contain numerous early larval melanophores. The D. nigrofasciatus ventral primary melanophore stripe develops further ventrally relative to the level of the aorta (a, J), and closer to the ventral margin of the myotome (J'), compared to D. rerio. Inset (J) shows brownish cast of an adult stripe melanophore (6) that originated in the early larval stripe. (E',J') Schematics of fish shown in E and J, showing melanophores associated with the adult primary melanophore stripes, and residual melanophores from the early larval stripes dorsally and ventrally, as determined by following individual melanophores from early larval stages throughout the image series (i.e. by analyzing cell lineage rather than by examination of final melanophore colors). For consistency with Fig. 2, melanophores that originated in the early larval pattern are shown in brown, and melanophores that differentiated during metamorphosis are shown in black. Dorsal metamorphic melanophores that will cover the dorsum and dorsal scales are omitted for clarity. Double arrowheads in B and F indicate deep, internal melanophores that are ventral to the notochord, or dorsal to the neural tube, respectively, and that do not contribute to pigment patterns beneath the skin. Standard lengths of larvae (mm): A, 6.7; B, 7.4; C, 8.6; D, 10.3; E, 11.5; F, 6.7; G, 7.1; H, 8.6; I, 9.4; J, 10.3.