Fig. 2. Expression of genes involved in ion secretion increased in both gills (A) and opercular epithelium (B) after seawater transfer. Na⁺/K⁺-ATPase _1a subunit, Na⁺/K⁺/2Cl^– cotransporter 1 (NKCC1), cystic fibrosis transmembrane conductance regulator (CFTR) Cl^– channel, Na⁺/H⁺ exchanger isoform 3 (NHE3) and carbonic anhydrase isoform II (CAII) mRNA levels are shown after transfer from brackish water (10% seawater) to brackish water (BW; handling control, grey bars) or seawater (SW; black bars). Expression is relative to the expression of EF1 and is normalized to pre-transfer brackish water controls. Data are expressed as means ± s.e.m. (N shown within each bar). ^*Significantly different from time-matched brackish water controls (P0.05); significantly different from pre-transfer (Pre) brackish water controls (assessed using a post-hoc test; P0.05).