Fig. 3. Relative abundance of 5'-UTR variants (v1, 2, 3, 4) in the gill under control conditions (12 h exposure to 100% air) and skin during control conditions and after 12 h of exposure to hypercapnia (1% CO₂ in air) in 10 mmol l^–1 Hepes-buffered water. Expression data were normalized to ng total RNA concentration. Different letters indicate significant differences in mRNA abundance between variants in the skin under control conditions. Data are means ± s.e.m. (N=6).