Fig. 6. Branchial hsp90 (A) and hsp90ß (B) mRNA levels for northern (NH, hatched bars) and southern (GA, grey bars) killifish exposed to heat shock. Control (C) samples were taken prior to experimentation, and handling controls (CH) were treated identically to the heat shock groups but exposed only to the acclimation temperature of 20°C. All mRNA expression data is normalized to the control gene EF-1 (values are mean ± s.e.m.; N=6). Different letters indicates significant differences between treatments but within a population, and an asterisk indicates a significant difference between northern and southern fish within a treatment.