Figure 5

QTL on chromosomes 4 and 20 control the number and spacing of early raker buds. (A, B) Left ventral row 1 gill raker bud number (left) and left ventral row 1 to 7 raker bud spacing (right) in 20 dpf fry (approximately 8 mm total length). Mean phenotypes are displayed for F2s homozygous for the marine allele (red) or freshwater allele (blue) of a chromosome 4 marker (Chr4_221) or chromosome 20 marker (Stn212) very tightly linked to the peak marker in both crosses (Additional file 7: Table S2). Phenotypes are back transformed residuals for a regression to total length for a mean length of 8 mm. N = 96 F2s from each of the Paxton benthic freshwater (PAXB) × Little Campbell marine (LITC) (A) and the Fishtrap Creek freshwater (FTC) × Little Campbell marine (LITC) (B) crosses were analyzed. * P <0.05, ** P <0.01, *** P <0.001 by a two-tailed t-test. Values are presented as mean +/- SEM. Additional information on these early time point QTL is presented in Additional file 12: Table S5.