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Abstract

Juvenile and adult guppies (Poecilia reticulata) of both sexes are camouflaged by an inconspicuous reticulate pattern. Additionally, guppy males develop exceptionally colorful and highly variable ornamental patterns during puberty. Sex-linked inheritance of several guppy color traits has been demonstrated, but the developmental pathways forming the guppy color pattern have not yet been discovered. We have investigated two independently segregating autosomal genes designated golden and blue. Golden guppies lack almost all melanophores at birth, but acquire some melanophores dorsally at later stages that eventually form an incomplete reticulate pattern in adults. This indicates that golden is crucial for specification, migration, differentiation or survival of embryonic melanophores. Further, early golden-dependent and late differentiating golden-independent melanophore populations may exist in the guppy. The male ornamental melanophore pattern is also affected in golden fish. In blue fish, a recessive mutation leads to almost complete loss of xanthophores. Adult blue males therefore lack orange spots. In addition, the black ornamental pattern of blue males is changed substantially compared with the wild-type, suggesting that both golden and blue play a significant role in the development of the guppy reticulate and male specific ornamental pattern. We have taken a candidate gene approach to identify the molecular basis of these mutations and have detected potential splicing defects and frameshift mutations in candidate genes.