Fig 1.
Schematic representation of crosses illustrating the pattern of color inheritance.
Cobalt blue and yellow-albino (F0) were initially crossed. Then, F1 yellow- and white-albino trouts were crossed with the same color phenotype, as indicated by loops. The first group produced an F2 generation composed of yellow-albino and wild-type trouts in a proportion of 3:1, following Mendelian segregation for crosses between bbAa genotypes. Crosses between F1 white-albino produced an F2 generation composed of white-albino, cobalt blue, yellow-albino, and wild-type phenotypes in a 9:3:3:1 proportion, following Mendelian segregation for crosses between double heterozygous BbAa.
Table 1.
Frequency of color phenotypes generated by crosses using cobalt blue, wild-type, and yellow-albino (dominant) rainbow trout.
Table 2.
Results of progeny tests to determine the genotype of blue trouts.
Table 3.
Frequency of color phenotypes in crosses with blue, yellow-abino, and white-albino trouts.
Fig 2.
External appearance and chromatophores analysis in the four color phenotypes.
A: Lateral view of wild-type, cobalt blue, yellow-albino, and white-albino female adults of rainbow trout. Chromatophores in bright field (left inferior) and under fluorescence (right inferior; xanthophores emit green auto fluorescence); the region selected for chromatophore analysis is depicted by a yellow box. Cobalt blue melanophores are more contracted compared to wild-type. Yellow- and white-albino are devoid of melanophores, which are indicated by blue arrowheads; red arrowhead indicates xanthophores. Scale bars indicate 25 μm. B: Number of xanthophores per section and C: size of xanthophores in the dorsal region of trouts from each color phenotype (same as Fig 2A). Different letters represent significant difference for p < 0.05 by one-way ANOVA analysis. Data are shown as average ± SEM. Five to seven fields were randomly selected and analyzed for each color phenotype.
Fig 3.
Comparative analysis of growth and pituitary morphology among color phenotypes.
A: Standard length, B: body weight, and C: condition factor analysis in females from the four color phenotypes (n = 14 per color phenotype). D-F: Relative pituitary weight in juveniles, adult females, and adult males from the four color phenotypes. G: Images of pituitary in wild-type, cobalt blue, yellow-albino, and white-albino juveniles with similar sizes and same age. Different letters represent significant difference by one-way ANOVA analysis for p < 0.05. Data are shown as average ± SEM. Scale bar represents 0.5 mm.
Fig 4.
Relative expression of genes in the pituitary of cobalt blue and wild type phenotypes.
A: Grow hormone (gh), prolactin (prl), deiodinase1 (deio1), deiodinase 2 (deio2), thyroid stimulating hormone (tshb), and thyroid-releasing hormone (trh). Expression of target genes was normalized against the respective β-actin values. Genes with significant difference by Student`s T test are indicated by an asterisk (p < 0.05). Data are shown as average ± SEM. B: Linear correlation analysis between the relative expression of tshb and trh in wild-type and cobalt blue phenotypes (same data from A), with linear correlation coefficient (R2) values for each group.