Fig. 5. A temperature-sensitive allele uniquely implicates fms in melanophore stripe disorganization and xanthophore reduction in hybrids. Tester fms¹⁷⁴ mutant D. rerio xD. albolineatus hybrids were reared at 28.5°C through middle metamorphosis, then were transferred either to 24°C or 33°C until adult pigment patterns had formed. (A,B) fms¹⁷⁴ hybrids reared at 24°C develop well-organized stripes and numerous xanthophores on the body (A) and fins (B, arrows). (C,D) fms¹⁷⁴ hybrids reared at 33°C develop poorly organized melanophore stripes and have fewer xanthophores on the body (C) and fins (D, arrows). Pigment patterns of control wild-type hybrids do not differ between 24°C and 33°C (data not shown). Scale bars: in A, 1 mm for A,C; in B, 150 µm for B,D.